Lining Up the Engine with the Chassis

[@RonaldFinger]

I am absolutely loving this series. Years ago, I followed as many tube frame build-threads as I could find. I was crazy about them and even ordered a race car chassis design book from the 60s in hopes of doing my own build one day. I had yet to see a well documented tube frame build on KZbin until I came across SK8215's build, and now yours. I'm really looking forward for what's to come!

[@digitalradiohacker]

Get that little pink Fiero finished! Between you and Bad Obsession, we're all going crazy!

[@smevox7490]

This build is the best thing on the youtube right now!!

[@TdrSld]

How dare you disrespect Project Binky like, go stand in the corner and think about what you have done. ;P

[@digginaustin]

You have not seen papadakis racing

[@smevox7490]

@@digginaustin Oh I have, not a BMW fan though, but the amount of work they put into that BMW is pretty sweet.

[@digginaustin]

Gotcha

[@digginaustin]

I was more just referencing it's quality of content

[@GSEShop]

THANK YOU SO MUCH FOR CONFIRMING WHAT I THOUGHT I KNEW. I had a vibration in my 68 Nova at speed and when I suspected the driveshaft and called a reputable vendor they told me 6 degrees down on the transmission output was too much and I needed to move it to under 3 degrees. I told them it should matter as long as my pinion is rotated up to match. They said this was incorrect and even with my LS it would vibrate if I set it more than 3 degrees. I argued about lifted and lowered vehicles and how they drop the transfer case or shim the pinion to match and I was told they would not help me until I corrected my transmission output angle. I beat myself up for months trying to figure out why this mattered, and you confirmed what I thought. Great videos I have been subscribing for a long time. Keep up the awesome work.

[@tracmick2699]

I really like how you have explained what you are doing and how your doing it and y your doing it that way. makes It a lot easier to understand,really love to set back and watch your channel .

[@Hutch-Monster]

I've watched your videos for a few years now starting a while back to pick up welding tips. I've watched a number of different things you've fabricated and have always enjoyed and learned a lot from your videos. You always present material with a lot of great detail and explanations which help me to understand why you make certain choices. Your latest videos really hit me at a great time. I've been working on a '69 Mustang Coupe RestoMod since 2014 (it's now with the painter). I'm currently working on a '59 Apache for my daughter which will need the entire suspension to be replaced. Although, I don't need to do anything like what you're doing, it really helps to understand why certain things need to be done to get everything to operate properly. I love watching your videos and especially your current project, keep up the fantastic work and stay safe during these difficult times. Thanks, Derrick Hutchinson.

[@Ryan_1997]

I don't know how 36 fools can dislike this. You provided a great amount of info that not many of us may know about. Lookin forward seein those custom headers.👍

[@mattaomartinez.9817]

so theres a handful of channels I watch for some gnarly tips in my field. Your obviously one of them, im amazed by how much information you keep putting out. I just started working again. as soon as I pay my rent again im donating money asap. I want you to do these videos as long as possible. Wish I lived near by so I could take a class.

[@dismalfist]

Quite simply the most useful and concise video on this subject I've seen. Thanks from the UK!

[@snr2707]

Best series online right now, hands down. Looking forward to the next video!

[@kevindangeleit6679]

Carb intake manifolds are cast with 3 degrees built in but since engine angle is 3 the intake will measure at 0 when mounted in the car. All older cars engine and trans are mounted 1 inch to passenger side for steering shaft clearance . If your driveline is perfectly straight trans to differential the rollers in the u joints wont spin.

[@RussellTelker]

Your last sentence is the important one, and is the reasoning for the angle in the carb flange. The engines weren't pitched to level the carb, the carb flange was pitched to level the carb. The output of the trans and the input of the differential need to match/oppose (ex: 3 degrees down on output, input is 3 degrees up). And MANY older cars had the engine offset, not all.

[@dsmguy4158]

Love this channel man, you're very informative and makes learning these processes a lot easier. I will be building a chassis jig now for building my "Time Attack" 95 TSI. Also thinking about starting a new channel to document the whole process. Thank you

[@oldandboosted]

So glad I found this video. We are starting next week to put a gen 3 Hemi with a motor plate in a 1974 Challenger no prep car.

[@veraciouspatriot4297]

Great video thanks! Working on installing a Buick V-6 and T5 into a ‘31 Model A pickup, and it’s been a head scratcher. Previous owner really did a hack job on it, and I’m trying to fix all the mistakes.

[@jdwisdom9433]

A lot of very important info that any want2be chassis builder needs to know. Thank you, JD

[@dan1906]

Great stuff, love the videos. I pretty much watch all your content, going back years. Looking forward to the rest. One thing though, raising or lowering the engine doesn't affect the roll center. Roll center is determined by suspense geometry. It is the axis by which the body rolls. Maybe you're thinking of center mass. Raising the engine will raise the center of mass and likely increase body roll while cornering, but not change the roll center.

[@TheFabricatorSeries]

I tend to use terms people reference whether completely right or wrong. I'll address that in a future vid since its technically irrelevant at the moment.

[@firstnamelastnameisallowed7943]

@@TheFabricatorSeries how about just saying "top heavy" thats one we all can wrap our noodles around instead of whatever it was dude said in the original comment here. I like the way you teach things, you give a basic overall summary of everything you need to do/pay attention to then you go in depth on each section of the build as it comes up in order. Cover everything but its not overwhelming like some other fancy pants people do. LoL 😆

[@truenotch]

I agree with this. It’s changing the mass centroid axis. Roll centre is purely set by suspension geometry.

[@reasonsvoice8554]

There's so much to this to actually get through to most people tbh

[@raginrednekk]

Sweet!!! You got the mandrel attachment for the rogue bender! That would mean, thin wall, aluminum, or show quality... Ooh... I'm excited for the next episode!!

[@Andrewlang90]

I love that your making automotive videos. I remember when I first subbed to the channel, you were making cages and such in your garage. This thing is gonna be the Hoonitruck, but on a much lighter platform. Can’t wait!!!

[@mikediamond257]

Lovin the detail to the small stuff that need to be sorted on these builds!!!

[@Strayacunce]

I love the way you explain all this stuff , so easy to follow. Being an apprentice welder wanting to get automotive this is amazing content so thank you.

[@chrisw8794]

I'm definitely going to use this video when I start my senior project for my program. tube chassis bimmer here we come

[@Tmbconfidential2]

Thanks!

[@jakepowell4058]

I’m building a 84 Datsun 200sx and I’ve been worried about the orientation and you’ve been a huge help, I have a 350 SBC I’m throwing in it so I’m a lot less stressed making mounts for it

[@eddyoddrod]

This is definitely a series I will be saving. I have a dream build I would like to accomplish and this just might help me see it to fruition. 👍

[@LonersGuide]

Love your content, man. Great, practical stuff that I haven't seen other people covering in-depth on youtube.

[@stevenmitchell6347]

Ecoboost turbo v6, 6spd, 8.8 diff, in a lightweight tube chassis pickup truck...AWESOME!!

[@chrisadair7760]

Right? Gonna be a terror on the streets

[@jbjunior2008]

Hi there! Greetings from Brasil! I have to say: THANK YOU VERY MUCH SR!!!!! The only one in the hole Internet with the complete explanation!!!!! You got a new follower... no, you got a new FAN!!!!! Question: where do I find the correct "U angle" for my motor? Thank you, again!

[@Ilsabug1]

Nice my last service van had an ecoboost and it would absolutely scoot. Too many LS swaps out there, it's awesome that you are being different!!!

[@fishhuntadventure]

I need to back up and watch the series from the beginning but I’m still working. Great stuff here

[@SteadArcFab_Ministries]

Nothing but sweetness!!! This build has been fun to watch!!!

[@3dmaxers]

I just started welding as hobby and love your channel, you inspire me a lot but have a question and cant find answer. Can i buy plasma cutting torch and use it with my tig/mma welder with compressor instead of argon?

[@Mikeyhunts]

Love the way you teach.... so easy to watch and learn. a+

[@pmccready291]

Interesting choice for engine I started watching your channel for the fab tech and ideas and truly appreciate the build you have started. I'm presently building a '76 Datsun 620 and phase 2 of the build will be improving the motivation - I hadn't considered the EcoBoost before but I have been thinking V6 Turbo...

[@Elvirth24]

I literally know next to nothing about building cars or trucks, more of a motorcycle guy, but this is very informative. Plus I have a sweet job opportunity coming up as a welder at a fab shop that does custom Jeep work and other automotive stuff, so this is technically research.

[@ajhartmanaero]

Hey man. Love the channel and love it more now with the EB swap. I swapped a 3.5 into my 99 Mustang that I road race back in 2016. I wasn't doing videos back then unfortunately. But yeah, I pretty much had to figure out all these measurements when doing my swap. For weight distribution and steering shaft clearance I did shove the engine towards the passenger side as far as I could.

[@aaronrodrigues6905]

I love it. When I mounted my engine all I used was a plum bob, tape measure, marker and a lot of reassurance on my measurements. First time doing it and seems like I did pretty good but Hopefully it works out. Still doing the wiring.

[@revolutionautoworks777]

lightweight platform and turbo power, it should scoot indeed. awesome project, it's tough to wait for the videos but looking forward to all of them.

[@robsimms2766]

What do you do if you want to build a custom body? Can you build your chassis first then your body? Love the video’s you taught me a lot thank you

[@slateslavens]

First, I'm loving this video series. I'll be building a new frame for my 48 Willys later this summer and I'm learning a lot here. A good example of a vehicle where the engine is offset from the vehicle centerline are the early Jeeps. All of the flathead powered models had the engine and trans offset 1.5 inches to the driver's side of the chassis to get the driveline to fit inside the _very_ narrow chassis. As for the pitch angle, you want the pitch angle of the engine/trans/transfer case (if fitted) to match the pinion angle of the rear axle. and DO NOT point the trans/transfer output directly at the rear diff.The reason for this is simply U-Joints. The physics of how u-joint works is that they speed up and slow down during specific angles of rotation as they turn through a single revolution. If the front and rear of the driveshaft aren't parallel (as seen from the side _and_ top, the driveshaft will have an annoying vibration that will be impossible to get rid of. If the trans/transfer output are exactly lined up with the pinion, it causes problems with the u-joints themselves. I don't recall ATM exactly what the issue is, it might be a binding issue, but I'm not positive. Whatever it is, it will wreck the u-joints in short order. As an aside, I learned pie cuts from your videos and made a set of double-Y headers for the V6 in my Willys. Thank you for the lessons!

[@billpapps4345]

I know your not drag racing. But, I found placing the engine Y to the driver side as much as you can,(at least HBody cars Door slammers) helps from twisting the car up like a pretzel on launch. Loving your Channel a lot of good info here.

[@vintagespeed]

ford mod motors are offset toward the passenger side to clear the steering rack. good vid!

[@larrysullivan6536]

Brilliant so well explained but very technical but it has to be right at the end of the day well done buddy can’t wait for the next video cheers Larrysullivan in London

[@edgarcorrea7866]

I love the engine choice I almost put one in my Miata but I had a question. I thought some pinion angle was needed to eliminate driveshaft hum?

[@supersevenn]

correct, you need both pinion angles to be the same to be balanced. cant have them at zero

[@joshhale2473]

This is good stuff I love that you're going a different route than most with the powertrain. I probably would have went with the 2nd gen 3.5 so you would have port injection along with direct for when you decide to start making big power as the direct injection alone has it limits. I have a 2011 gen 1 3.5 eco in my flex and it moves it around nicely for its size

[@hamper116]

And here I was thinking I should ls swap my 300zx but you woke up the idea that I had in the beginning, I worked on these engines and they’re great

[@dwaynewest726]

I'm doing almost the samething to my 95 hardbody, new chassis, new drivetrain which I dont have yet and new layout, going AWD, I'm so pumped to see how u finish this one my instructor

[@rideakhomie]

Are you using the original suspension? I have a 4x4 and been dreaming of converting to coilovers, long arms front and 4 link rear. These truck could use more wheel travel.

[@dwaynewest726]

@@rideakhomie I have a design for a Baja style setup if u like

[@bobross07]

Dont take this comment the wrong way. The ls engine is an amazing and easy platform. That being said...thank you for the love of god for being original and NOT using it.

[@krusher74]

you cant even buy a vehicle in the UK with a LS, how do our cars even work!!!!!!!

[@bobross07]

@@krusher74 lol hey but you guys have some killer ass diesel engines we can't have 😉

[@Andy-Against-The-World]

@@bobross07 nah, I'd prefer a duramax or proper power stroke over the weedy little diesels we have these days

[@mabamabam]

@@krusher74 You got a very small number of Vauxhall badged holdens with LSs

[@Nowayjose-z2r]

Not a fan of the engine choice, but also agree 100%. No, I don;t know what I'd drop in but yes SB(whatever) and LS are WAY to common. Nice to be different!

[@larrysullivan6536]

Absolutely brilliant love this guy he knows what he’s talking about I can’t wait to see more cheers Larrysullivan in London

[@chaseweeks2708]

I thought that part of the engine angle consideration was matching it to the pinion angle in the rear end, or maybe that is coming up when you get to that point?

[@TheFabricatorSeries]

You're backwards. The pinion of the rear pinion matches the trans. We dont match the trans to the rear. We're not there yet 👍

[@chaseweeks2708]

@@TheFabricatorSeries Ok, cool. I'm really looking forward to how this all plays out.

[@timjackson5555]

Only major thing I was ever concerned with was the driveline angle 3°-5°

[@TdrSld]

Like he said, in the old days of toilet bowls on top of the engine you would place the level on the carb flange on the intake manifold and set it to 0* degrees on the x and y axis. With EFI you could hang that engine pointing up and as long as you figure out the oiling needs you just send it lol.

[@TdrSld]

@@timjackson5555 Driveshaft angle is not really a hard point, the hard point is having at least .5* degree of working angle in the u-joint/CV-joint to keep the lube moving in it. You could place the engine and pinion in the same plane, center line to center line and literally put in .25* degree of down for the engine and .25* degree of up on the pinion and have the driveshaft dead nuts level along its length and still get to the .5* degree total working angle at each u-joint/CV-joint.

[@JanELohne]

When building drivetrain from scratch and talking about engine angels. I think it's also important to mention the importance of drive shaft angels and line up. And if you can't laser line up gearbox output flenge to the diff you need to make sure that the driveshaft U-joints have the equal amount of angel on each end (at least within spec) to prevent severe vibration. Angled driveshafts increase and decrease speed twice for each revolution. So it's important to allow both ends of the shaft to increase and decrease speed the same amount.

[@gt-f100irunthis6]

Doin a 09gt-500 swap into a 72 F-100 and this drive train sits over to the passenger side. I was taken back until I did more research and it’s factory ... I enjoyed the info brother.

[@RadDadisRad]

Hey, you should go ahead and do the water pump and timing chain if you haven’t already. Also stock plugs are motor craft SP534 plugs, go ahead and get the next range colder of SP542 and gap them between 0.026-0.028, it’ll help with idle stumble and rev hang.

[@coryhalvorson8874]

You a tech, or just been through it with the same engine?

[@jcnpresser]

Eco boost 3.5’s wear out spark plugs early, around 60-75k. The water pump on his engine is external, not like the explorer and sho. Would be a good idea to at least pull valve covers to see if engine is clean. If not I’d pull cam phaser solenoids and clean or replace them.

[@fordpower9917]

Amazing video man the information you give is very helpful thanks for breaking it all down. Cant wait to see your truck done.

[@macmcmillen6282]

Great video, especially the explanation of the various angles and roll axes.

[@kevinhornbuckle]

I like the overview at the end. This helps keep the goals in perspective.

[@dronedadfpv4541]

A lot of the 80’s gm chassis actually had the front crossmember offset about 3/4” to the right which set the engine and trans offset in the chassis. I’ve been told it was to make the U joints work, steering shaft clearance.. etc. not sure why but I’ve confirmed that it is. Interesting stuff!

[@rickgehring7507]

A lot of Rear wheel drive engines are off set to the Passengers side to maintain a straight centerline with a the rear differential.

[@BillPhillips4]

FYI, many Chrysler passenger cars from the 1960s - 1970s were built with the engine positioned an inch or so to the right side (not centered) to allow clearance for the steering shaft and brake master cylinder power booster.

[@thirstquencher3203]

I'm a little late to your channel however this is by far the Best FABRICATION channel yet!! So much knowledge in every video and such amazing skills🤯! Thank you so much man keep up the amazing work/content 🔥🔥🔥💪💪👏🏼👍👌

[@dhanwatiesukhai2524]

Hello Justin, awesome illustration of how you are doing your build. Hopefully some good day you can do a Trike build with the engine in front. I’m really wanting to build one. I’m considering using a Subaru engine and rear end (Andrew).

[@jcnpresser]

I knew it was a ford transmission from last video. I was thinking 2.3 eco boost, but you got the big daddy eco boost. Should be an awesome build, that engine makes so much low end it’ll probably be breaking the tires loose everywhere!

[@cj7girl280]

Thanks for the video... Any idea about the pitch angle for a 4.3 v6 gen 1 fuel injection GM engine with th700r4 transmission in a 1976 cj7 jeep? I know the engine has to be about 1.5" towards the drivers side (to allow front driveshaft room) and that the engine needs to be at 5-7 degree tilt back too. Thanks again.

[@hutchdw77]

I’m very excited for this series. Thank you.

[@RadDadisRad]

Also XDi-60 high pressure fuel pump is hard to beat and DuetschWorks makes 1700cc matched injectors. The torque curve on the horizontal ecoboost is phenomenal. The thing makes a ton of stink in my 2015 expedition.

[@berlina117]

got some good tools there. I enjoy your channel. Ive just started out tig welding. been doing a few alluminium projects.

[@ifell3]

Great info, nice to see you using some flux core on the quick and easy bits!!

[@ElrodsGarage]

Dang! That's a great explanation of things and stuff. You got all the good toys. I dig it!

[@turbovolvos40]

I have a welding question. I have seen a few KZbin videos showing cold welding. Do you know what this method entails, and if it can and/or should be done with a TIG welder?

[@rennkafer13]

Oooo, an upgrade from the M600 Rogue... will be interested to see how you like it.

[@michaelbarnett7986]

Justin love Your Work. You are a talented welder/engineer and presenter. if i can throw my twobobs worth in on your angles, one of the reasons the pitch angle or v angle is set is in correlation with the final drive pinion angle , if you are using a "Hotchkiss" Drive system (Spelling from memory) that entails cross and yoke universals, to prevent vibration the angles at normal ride height of the power unit and pinion should be as close to each other as possible. However if using a CV drive this is not as important. Just my takeon this, Looking forward to the next episode Cheers Mate. Michael./

[@DStead2239]

Most vehicles have their engines mounted slightly offset to the passenger side, Makes RHD vehicle conversions slightly more difficult as there's less room for steering components and also the weight bias with engine and driver being to the right of the centre line.. Same reason some LHD drag vehicles in RHD countries are preferred as driver weight opposes torque reaction.. Also, gearbox output and pinion angles should be aligned at ride height.. Awesome build👊

[@marksexton1340]

Thank you for this video, finally some answers that make sense. Level at the base of the carburetor, makes all the sense in the world... I've had multiple guys, tell me multiple things....3 degrees, 6 degrees... Thanks.

[@preludedude4765]

Desperately awaiting the next part to this

[@gabrielhermosillo4866]

Is the pitch of motor/trans not relevant to drive shaft alignment? Or can the ujoints just take it without excessive wear?

[@ryanworkman5229]

Nice engine choice, not so common here in Australia but I happened to work on an Expedition with one fitted, I thought it went well in it's natural home, should be a weapon in a Triton. As for mounting the engine, most early Mazda rotaries are offset to the left side probably for exhaust clearance, and older Toyota Landcruisers point to the left noticeably I believe for front diff housing clearance.

[@davesmith8936]

Absolutely LOVE this series! And you're doing great self filming! Keep up the good work. Your content is even better while we are trapped at home! LOL!

[@oscaraguilera2181]

I'm a member of creating a baja vehicle, but recently on a competition, I watched how some other teams have a particular way to install the engine, it remains with an angle. Do you know what are the effects of doing so?

[@station08]

Great lead in to the new bender. Cant wait. It looks sweeeeeet !

[@MathsatBondiBeach]

As a retired mathematician who used to race rally cars and built the last one with help, I got a mild hard on when you mentioned "Euler" angles (pronounced "Oiler"). You did a good job of explaining the basics. Try aligning a prop shaft in a trawler - that is bigger than Ben Hur!

[@s302jzget]

What if your v-measurement with your trans tail shaft pointing too low and your rear axle is tucked up the chassis(lowered). How do you go about correcting the driveline angles? That’s one of my issues at the moment and thinking I’m going to have to redo my motor mounts and drop the front of the engine lower so it will allow the rear to point upwards so I can achieve better driveline angles.The way it sits, the trans is hitting the tunnel if rear section is raised. 🤦 I would hate to cut up the tunnel and redo it but I might have to.

[@allianceofvengeance]

Talk about quality content! I love your videos.

[@turboflush]

Hopefully you ordered the oil pickup and gaskets also with that pan. :) Love the engine choice.

[@TonyHammitt]

Nice engine choice, I think you'll have a lot of fun with the truck with that in it

[@wcmwfab935]

Turbos going to be awsome build can't wait to see.

[@dwheeler6969]

Hey justin great educational videos love the whole series and everything you do man ... keep it classy and rock on

[@LintRoller86]

let’s say my garage floor is level… should the vehicle itself be level on stands or should it be sitting on its suspension and tires?

[@jasoncampbell4723]

Oh the Big Dog bender!! Nice. Nice motor choice, I know a guy who gets 917HP out of one of those. Should be interesting.

[@ernestkosek4455]

Have watched numerous of your videos on tig welders etc. What is your opinion of the everlast 250 EX as a first tig machine? Im having a hard time justifying and extra $1000 for the 250 EXT Appreciate any insight and enjoying your chanel. Thanks Ernest from Montreal

[@aaronhayden1780]

Could you do a review on the Hitbox 200 mig/tig/stick welder on amazon. It’s $350 and seems like a decent unit

[@HermitFab]

One thing to bear in mind when setting the engine/gearbox angle (tilted up or down at the rear) is the diff pinion angle. For this build its not a problem as you will be able to adjust it. But if you were doing an engine conversion only and the pinion angle was not easily adjusted then you need you gearbox angle to match the pinion.

[@dewdsux6127]

I knew it!!! I saw it the other day and said that's a dadgum EcoBoost lmao. I love it bo. Can't wait to see it going.

[@leonkane8240]

You explain things really well.

[@aaronyoung8028]

Hi Justin, any updates on this awesome build? I'm on day 28 of full lockdown, and would watch you just rolling a welder towards your chassis jig 🤣 Looking forward to watching your dream truck come together. Stay safe! Cheers Aaron.

[@rover215]

Extremely good info- glad I found this!

[@retep8891]

You should get the intake manifold from the SHO as well. It kicks the throttle body at more of a 90 degree angle and can give you more room for your radiator and other plumbing at the front of the engine.

[@retep8891]

You should also sell the manifold flanges because I can't find them anywhere on the internet and they would have been really helpful when I put an ecoboost in a ranger.

[@RadDadisRad]

Won’t work. Different cylinder heads different bolt pattern

[@RadDadisRad]

Transverse ecoboost only has VVT on the intake the horizontal ecoboost has VVT on the intake and exhaust.

[@RadDadisRad]

Transverse ecoboost cylinder has the same intake bolt pattern as the cyclone series of engines.

[@retep8891]

hmmm, okay, I never had to the two parts next to each other. They looked the same on the Ford parts page. Still would like the flanges though ;)

[@WhatsCookinToday]

I have an 85 foxbody with a 383 stroker SBC. The engine sits 4” to the left.

[@crazyeyez1502]

Curious.... i understand the reasoning for the different front sump oil pan, but would that have any effect on a front engine, rear wheel drive vehicle during hard straight line acceleration?

[@jamesdow4866]

SGT Nick H unless there’s some serious baffling in the pan, acceleration g forces will rush the oil away from the pickup. Seen it on a few cars that took fwd engines and used them for a rwd application.

[@crazyeyez1502]

@@jamesdow4866 that's my thinking.

[@00ramman]

A lot of Mopar vehicles actually have the engine closer to the passenger side. They did it to give more room for the steering and exhaust so that means the rear diff is also more to the passenger side not in the center.

[@ToshiiTheBlack]

Bro thank you!!! I was trying to figure out how to put this flat 6 in this Nissan for the longest

[@michaelwhitfield5431]

Foxbodys are an example of being offset from the centerline of the car.

[@NorthViewModelShop]

Thank you for the info on engine pitch. I’m putting an LQ4 into a 68 amx and at zero degrees the tranny is inside the car. At 5 degrees it’s pointed at the pinion

[@FrogsGarage]

I will say a lot of factory engines are offset to the passenger side and they do that for more leg room and stuff for the driver also helps balance weight from side to side on some vehicles cause they have the weight of the fuel tank and driver on the driver side plus other things. Also why some vehicles have rear axles where pinion is offset to better line with the engine.