How To Destroy Your TH400 Transmission

[@PaulPitrone]

As a teenager, I am a Victim/Veteran of the rubber cooler hose method of destructing a Turbo 400. Much like any other traumatic method of learning...You only do that once. At 68, I still have the car (1970 El Camino), 46 years and counting. Wish the internet and your videos were around back then, you would have saved me all that heartache. Thanks, and better late than never.

[@stevecarroll3991]

We did participate in Sick Week and did have problems with our th400 so in the quest to learn everything I can about them that’s how I stumbled on to your channel. I appreciate the simple explanation of how everything works and we’re going to fix it ourselves to be self reliant on these drag and drive events. Reassembling video’s to help get things right are very appreciated and yes we’re running mid 8’s in a 3700lb 3rd gen so you know what kind of power it takes to get there.

[@mountainsgarage]

Awesome, glad to help. I would love to fix it on the route, but will have to settle with doing helping remotely for now!

[@darrenlavigne6849]

Another great vid Sean Thanks for sharing all the knowledge and insight. You have inspired me to rebuilding/refreshing the th400 in my ‘66 LeSabre. Cheers

[@mountainsgarage]

Awesome! If you need help holler!

[@MHolt3573]

I thought to myself at lunch today, I hope Shawn has a new video this afternoon and sure enough you did. Thanks for the info. It gives me and my wife's uncle that I work with (he build transmissions) something to talk about. He built alot of GMs back in the day

[@mountainsgarage]

Love it!

[@Dave872010]

My brother had a 400 come apart big time yesterday. Doing a burnout in 3rd gear. It absolutely exploded. Incredible carnage. Beat the heck out of the car. Ripped the bellhousing clean off of it. Input shaft pointing up at an angle. Tailshaft busted off with what I believe is a clutch drum hanging out the back of it. Bent a gforce crossmember. Messed up the flywheel, ripped the oil filter off the engine and broke the block on his fresh $14000 Sbc. Torque converter was laying on the ground like you set it there and the remnants of the transmission was turned sideways laying on the ground. “1000hp” 400 from a local shop. Not sure what caused it so not pointing any blame but it sure is impressive.

[@thisisyourcaptainspeaking2259]

The burn out caused it.

[@christophersanders5007]

Another thing I find to be a good upgrade is using the Sonnax imidized plastic check balls. The steel check balls can tear up the valve body ports pretty good.

[@BigFun4Life]

Thanks again Shawn for all the info you share..Always enjoy watching your videos…

[@johnhenryholiday4964]

Great information.... I had heard about tractor oil.... Im assuming (bad idea to assume) that your talking about using transdraulic oil for a transmission....

[@MrTheHillfolk]

15:20 Oh man , i just finished a cooler install and used AN fittings and hose for it all, i hate that clamp and go fuel line trash. This was a "kit" with an adapter, and a couple of hose barbs for 3/8 hose. The adapters were drilled for 1/8npt, and by eye the 1/8npt to -6 aluminum adapters i got had a horrendous restriction compared to the brass, and even that was marginal. I got some 1/4npt to -6 fittings and drilled and tapped the adapters for 1/4"npt. I got some flow back that i think would have been missing. Not a bad idea to check any kind of fluid flow circuit, and see if you can do a little "porting" so to speak. It couldnt be happier as im seeing average drops of 70 degrees and it even shifts nicer now. I wasnt gonna be that guy on the roadside with a piece of blown out rubber hose ✌️

[@adrenalinejunkie126]

Thanks for all the tips brother! TH400 build coming soon! Lots of your videos put to use!

[@BBBILLY86]

Great video. TY. I run a TH400 in my big block drag Monte SS and big block street Nova. Never knew the don't shift from 1 -2 on burn out. That alone will save a ton of money and hassle. TY

[@davelowets]

Just start your burnout in 3rd if you have a manual V.B.

[@highproof2735]

Subscribed just because of all the turbo hydro tranny info. I learned so much here from not throwing the tranny into neutral at high speeds and all the ways to harm it that I didn’t know about. Amazing channel you definitely deserve a lot more exposure and I will be recommending any chance I get!

[@mountainsgarage]

Thanks for the kind words!

[@MrTheHillfolk]

Late 80s and a buddy got a 350$ 79 Impala wagon ,i think it had a 305/th350 if i recall. Anyways, one day we are rolling along about 45 on this back road that has that greasy tar all over it which is great for burnouts and leaving long stripes. He goes,watch this, and shifts it into neutral, blipped the gas and whacks reverse and boards the pedal😂 One spinning tire to stop your forward motion from 40-45mph takes 4-500 feet in case you were wondering 😂 Be sure to let it one wheel peel in reverse till it hooks ,and dump it in 1 and it leaves 5 feet of rubber 😂 We did that probably 5 times a day for most of the summer ,and the old girl got so tired it wouldn't rev to 3500 in neutral from floating the valves so much. Trans hung in like a champ.

[@Shop209]

I just signed up for RMRW and I have a TH400 that was built in 1998 then sat on shop floor until 2021. I installed it and it works fine so far but I have only driven it a couple of miles. Other than a cheetah RMVB, I have no idea what has been done to it. Any advice on specific mods for drag and drive events? Thanks!

[@BElder762]

Would like to see you and Richard Crich,just talking about th400s.You both are masters in your trade!

[@hooligans_garage7465]

Appreciate the awesome videos! Just finishing my first th400 for my turbo Ls mustang. Wouldn’t have tryed if u didn’t have such good info!

[@mountainsgarage]

Glad to help in a small way!

[@timdontwannasay5889]

I ALWAYS learn a lot from your videos! Thank you so much! 5 items I picked up from just this video alone!

[@joebenhayon8774]

Just completed assembly and conversion of a 4x to 2x th400. Problem, the output shaft is damn hard to turn counterclockwise, as you look at it from the rear. Won't turn clockwise.... Normal, or do I need to pull,it apart and double check clearances? All clutches are fully bottomed out and front pump seated. I Can turn the input shaft easy. Your videos have been a great tool for me.

[@joebenhayon8774]

Well, I started disassembly. Got down to the center support... as I was loosening the support bolt, could finally turn the output easily.... So, how do I prevent this problem from happening again as I go back together?

[@russellbarton7565]

I have a 1990 gmc Grummon Olson step van with a TH400 3 speed transmission with a 210HP vortec tbi crate motor. I want to out more power into this motor but I don’t know how much power the TH400 can handle. I’m only looking to do 300 hp so I’m assuming it will be fine

[@mountainsgarage]

No problem, turn it up!

[@keithwalden7718]

Have a number of transmissions to identify that have been stored many years. I want to clean exteriors without removing any ID info. At least 5 should be th400 and 5 possibly th350. 3 Torqueflites and 2? 1 th400 done by Russell in NH 1th350 done by Pinard others were not bad but removed as I parted out vehicle they were in. Now they look pretty bad but am thinking correct cleaning agent will let me at least figure out which is which. And make more presentable.They should all be rebuildable. Several may be good to go after cleanup. Will paint with Aluthane most likely once cleaned an ID'd. Thanks Keith

[@menoaz]

So what do you recommended we do after the traps with the throttle in a manual th400? Ive always just whomped the throttle a couple times until i slow down.

[@crawford323]

What if a 73 LS4 454 came with aTH400 with a performance package with a posi-trak 3.36/1, did Chevy build it robust enough 50 years ago to handle 390 ft/lbs of torque?

[@mountainsgarage]

Even in stock form the TH400 is stout.

[@danieldavis5242]

My truck th400 shifts hard while accelerateding I'm not trying to hot rod it just normal driving around town jerks around but does drive around okay I know I replace the 6.2 diesel engine for a 454 big block but after the engine swap I noticed some transmission issues

[@danieldavis5242]

I bought a torque converter for the 454 engine swap not sure if I got the right stall

[@mountainsgarage]

Try a red stripe gas engine modulator. Around $15 bucks.

[@geraldstanley6953]

*Shawn. Also got a whirring noise when cold, at idle and throttle. Pump?

[@mountainsgarage]

Do you have a screen type filter?

[@johncarter9054]

@@mountainsgarage Why would that make a difference ? Just curious because I have the same issue and just changed fluid and it had a screen filter. I was just wondering what difference it would make ?

[@timothyheller2580]

Thanks for the info very helpful I have built several transmissions. I really enjoy your videos

[@drjf1]

Hi Sean. Quick question. .011 or .21 for front end play on a full race tb turbo 400. Also has a bte bell housing. Rear is .008. These are my choices. Thank you for the help.

[@mountainsgarage]

Be sure to jack up on the output shaft when checking the front end play. If you have done that choose what gets you close to .002-.005 looser than the rear .

[@larrythompson7802]

I thought that w/ a manual v.b. when you go thru the traps you leave it in 3rd. Did I inderstand this wrong?

[@mountainsgarage]

@@larrythompson7802 That is correct.

[@larrythompson7802]

Thank you. Besides your current videos, I go back and watch the older videos like this.

[@mountainsgarage]

@ Great, thanks for watching!

[@thewrench324]

Great topics! Thanks for sharing

[@samuelrodriguez8198]

Hello friend, I saw your video and I would like to get a question right, I took my th400 transmission to be repaired but it did not make the third change, I already changed the governor, modular, converter, and it continues the same, now to your great experience what will be the problem for which Does the third change not make the transmission? please help

[@billblevin4391]

My th400 spins out second gear under full throttle only. Anything less than full throttle second holds fine, shifted manually second holds fine.

[@mountainsgarage]

Sounds like it needs to come apart. :(

[@terencevictoria8933]

I have a th400 on my 90 p30 with 40k miles and I lost all forward gears under regular driving conditions.stuck on the side of the road and trying my best to get this thing going coz it's a road hazzard.i live in it too due if it makes a difference.i need help on to what I can do to get at least 1 gear Goin except reverse so I can move to a sager place to deal with it.its a class a bus and towing it is the last option.id rather put the money in to fixing the trams instead of handing it to a tow truck driver which is very costly to bring a lowboy to transport it and I'm already low on funds..sos

[@mountainsgarage]

Check the simple stuff, fluid, linkage. But if that checks out the damage is most likely internal and will need to be removed and overhauled. Sorry about your predicament!

[@DWBmotorsports]

A lot of guys kill the engine at the stripe so they can read plugs. How does a guy do that without exploding the drum? Do all autos do this? C4? Glide?

[@drjf1]

Have you used the alto power packs. I am purchasing the 7-6-4 deal for a 1200 build. Patc said it’s the way to go. What’s is your opinion. Great channel learning a boat load. Keep it up.

[@mountainsgarage]

Those are a fine choice, I have used some. I take many transmissions apart with them and they seem to last.

[@drjf1]

Would you recommend anything different.

[@drjf1]

Thankyou for the quick reply

[@mountainsgarage]

@@drjf1 Any good quality clutch is fine. I have only tried one set of blue clutches, expensive. They left in a transmission and I don’t expect it will be back. I use middle of the road Alto and Borg Warner green clutches.

[@young11984]

When i was running a C4 when i did a burnout i would go from 1st to 3rd nearly as soon as the tires rotated(manual vb) so would that save second gear issues with a th400? I whole heartedly agree with you on the rubber or transmission hoses, 90% of the trans leaks at our track is from old ass fuel lines for trans cooler hose. They will spend their kids lunch money for braided ptfe fuel line front to rear but put that rubber shit on there trans coolers

[@davelowets]

Just do your burnout in 3rd. That's what I do..

[@davelowets]

If you run a deep pan, and purposely run it a quart low, make SURE you also install a filter spacer, or it won't pick up fluid.

[@timweb1510]

Cautiously watching this hoping I don’t have problems

[@ijteague]

So to be clear. The transmission is FULL at the pan gasket?

[@mountainsgarage]

Yes

[@ijteague]

@@mountainsgarage thank you. Because my dip stick shaded area is up in the tube still. Good to know.

[@406MenaceRacecar]

I did a lot of 1st gear water burnouts at the track before learning to start in 2nd. Edit: also i was trying to n figure out how to read my plugs and couldn't figure out how to put it in nuetral after a run so i can get a good plug reading... that's when my trans guy told me I'm an idiot and don't think about doing that with a th400. People don't know that- i talked about it and got accused of being a rookie not knowing what I'm talking about. (I used to have the forward pattern VB but now it's rev VB with brake that I never used yet)

[@waynew2831]

I am converting mt 350 TBI to a carburetor. Can you tell me what I need to do with transmission control.

[@mountainsgarage]

What year and transmission do you have?

[@waynew2831]

1988 Chevy C3500. TH400@@mountainsgarage

[@reminoel483]

Precision transmission brings up pump wear caused by excessive pressure in every th400 video they do. Im gonna block off the modulator anyways 😅

[@mountainsgarage]

And never look back!

[@n2fastcars635]

Question about the comments about pump pressure not wearing out the pump? I have seen another KZbinr trans builder say you can't run a trans brake th400 on the street very much at all without wiping out the pump gear because of high pump pressure. Is this what you where eluding to when taking about pump pressure not being bad? Maybe a little more insight on what is bad and not bad in your opinion. Thanks great video!

[@mountainsgarage]

I have not experienced any pressure related pump wear. I install many transmission brakes and many get driven on the street.

[@funfun8095]

That's probably the Precision Transmission idiot from Texas. A lot of people have called him out on that! Jake at Jake's Performance has even called him out on that. Doesn't affect the pump. I know a guy with 10k miles on his, nearly all street miles.

[@PackardDaveH]

Love your videos.....very insightful!

[@mountainsgarage]

Thanks!

[@robertweitlauf4653]

Hi Shawn, what pump would you recommend for a 400 behind a 800hp bbc. and what belhousing do you use, i have an 8 bolt case. i have watched your videos on belhousing choice put i cant remember, sucks getting old. thank you. keep the videos coming. cant wait till the Novas are done. trying to get mine up and running again.

[@funfun8095]

Stock pump, modified.

[@davelowets]

I use a JW Ultrabell behind my 1000 h.p. big block. I have a 6-Bolt case which did have the boss behind one of the pump holed, which I drilled and tapped, so now it's a 7 bolt. No issues with the setup.

[@geraldstanley6953]

Sean, I have a 1989 Jaguar XJS with the TH400. Slipping in 3rd and juddery in reverse. Thinking about rebuilding it myself. The case/bellhousing is different from GM. Any advice? Is there a suitable rebuild kit? Stock v12 motor, 300HP. Thanks!

[@mountainsgarage]

A nice transmission inside in the Jags. Any quality rebuild kit.

[@dantheman1998]

@@mountainsgarage whats inside that Jaguar th400 that makes them different?

[@BigMikesGarage]

You should put an LSA on your Dodge and go do a drag and drive event. I think it would be a blast!

[@dantheman1998]

You talk about alot of race stuff but what about street strip? Something that's comfy to drive but shifts hard when you need it to and holds power?

[@mountainsgarage]

In the TH400 playlist on my channel page I have some street stuff. Need to do more!

[@caddydaddy6728]

If type f fluid is not so good why would a shift kit manufacturer recommend it for their shift kit?

[@mountainsgarage]

Many opinions on fluids. Me personally I have handled enough Type F.

[@elsdp-4560]

Thank you for sharing.👍

[@cameroncashatt692]

your comment of type F is interesting. because i was told by my last rebuilder to use type. I hope that wasnt why 3rd gear wasnt very good at the end.

[@joelbower8908]

I’ve been watching a ton of your videos as I’ve been rebuilding a th400. Well it was a fresh rebuild from someone else. It had a fmvb with no brake. I installed a 34 element sprag and a billet forward hub as well as a speed master rvmb with brake. I haven’t put it on the ground yet but on stands I have no reverse with brake activated. N-3-2 all seem to work but 1st locks it up like the brake is activated without power to the solenoid. Any idea what to look for?

[@bulldogmyth6147]

Did he ever get back to you?

[@joelbower8908]

@@bulldogmyth6147 no. Sprag I purchased on a drum was installed backwards lol

[@joelbower8908]

Had my gear selections off as well with what gears it was acting up in

[@davelowets]

I had the same issue once, and it turned out that the spool valve behind the solenoid was too long and was engaging the brake all the time. Grinding about 1/4" off the solenoid side of the valve fixed the issue.

[@Caleb_S26]

Is there anyone in Texas who can rebuild my th400? My 85 suburban went through two 700r4’s and now 4 years later I have loss of power and reverse delays in the th400 I put in it

[@veggiepowered]

I'am Your Newest Subscriber Great Videos My 1988 G20 Camper Van Has A TH400 wish it had 700R4 it drinks fuel with no overdrive

[@mountainsgarage]

Welcome! And Thanks!!

[@Blackbullet_racing]

Will the stock direct survive at 8000rpm ?

[@georgegrimm4952]

I bought an used expired SFI TCI shield from Ebay just for safety and I don't even drag race, its on the street only.

[@mountainsgarage]

Good idea! That is an item I think it’s silly to have an expiration date.

[@flinch622]

@@mountainsgarage It is stupid: metal doesn't have an exiration date like milk. You would think tech can inspect fasteners, check thickness, and have a nice day - just the design needs acepted certification. Now, seat belts? That is reasonable [yet annoying]- oil and dirt over time can degrade both stitching and material, and cleaning up later won't cure that.

[@mountainsgarage]

@@flinch622 Even seat belts. Good for 5 years in a Stock Car with no windows, and they hit things! I am pro safety, but…

[@Elcoboyz]

When does the video start?

[@YourTransmissionRepair]

Old school.

[@jamieknight9636]

Thx for the vid Shawn. Last month I fitted a line pressure sensor in the t400 in my HZ for logging and find it's running around 170psi on a pass. would you suggest dropping the pan and lifting it? I should be able to shim the existing spring shouldn't I, do you know what thickness shim generally works to lift the pressure?

[@littledeel]

If doing a burnout in first gear with a turbo 400 is detrimental to it then why is it used and drag racing applications where most of the time people spin the tires from 1st gear?

[@mountainsgarage]

With no load in the waterbox you start in second and shift to third then drive out to avoid damage. There is a load with minimal spin off the starting line. It is the No load free spin that hurts the transmission on a 1-2 shift.

[@richiec4120]

Would a stock drum and clutch pack stand up to 1200 hp ..nitrous motor ??

[@funfun8095]

Yes.

[@richiec4120]

@@funfun8095 👍👍Thank You !!

[@tacotimeracing6638]

Sean thanks for the videos that helped me build my first th400 for "Taco Time"... It lasted through RMRW 2.0 last year, several street races, Sick Week, aprox 3,000 miles of driving with and without pulling a trailer, but unfortunately with some new found power it broke the first pass at Summit Midwest Drags last week. I am back going through the videos as I assemble a better version with your help! Thanks so much for sharing, and look forward to more content from Mountains Garage.... Aaron/Taco Time Fairmont

[@mountainsgarage]

Glad to be along for the ride!!

[@billypaige9570]

Do you have any experience with building a 2 speed th400? What parts needed or parts not needed? Thanks

[@Boostismyfriend]

Love it

[@funfun8095]

Best benefit of hydraulic fluid is, it's not flammable. Use it in all my builds.

[@alchampion340]

What tractor fluid would be best? I’ve been considering this route for a while.

[@funfun8095]

@@alchampion340 I use John Deere Hy Gard. Some people use Catrol blue. Any good one will work.

[@flinch622]

I thought about that but... what about seals? Not all hydraulic fluids get along with certain materials. Have you noticed any change in stall speed?

[@funfun8095]

@@flinch622 Nope.

[@jasonjennings5833]

More videos please

[@mountainsgarage]

On it!

[@notsure7874]

I have seen some guys that kill the engine at the traps so they can read plugs - after of course clicking on the clean neutral. Which is 100% defeated by shutting the engine off because the pump now has no pressure. Don't do that.

[@benjohnson3700]

you must be living in bible belt, sure talk a lot

[@mountainsgarage]

Be kind of odd not to say anything.

[@robwwhit3453]

Second gear sprag...ha

[@Schlipperschlopper]

´Modern ATF suck you need DEXRON 2 and ONLY DEXRON 2.

[@skutahuniai4830]

This may sound anal but you appear to be part of the group that continues to call a roller clutch a SPRAG. A sprag was invented by Borg Warner and the name itself designates it as being with the "figure eight" elements. There is no such thing as a "ramp style sprag". A sprag is a sprag, and a roller clutch is a roller clutch. There is also a mechanical diode. They are all one way clutches.

[@mountainsgarage]

I believe the word sprag was in the dictionary long before Borg Warner came along. Among the group is General Motors, who regardless of style referred to either as rollers or sprags depending on the manual page. They also refer to the ramps of the roller style, also calling them teeth. Fun Fun!

[@skutahuniai4830]

@@mountainsgarage Not going to argue with you about this but I am right. I have researched this many times. I didn't just pull it out of my arse. I also have many GM manuals and a quick check in one area they describe a transmission as having a "sprag(or in the case of older models, a roller clutch)". Exact wording. Here is a quote from a bearing design firm. "Ramp & roller clutches are used for applications with low-to-medium overrunning speeds and for indexing . Sprag clutches are the choice for applications with high overrunning speeds and for backstopping . When the outer race is the driving member, this is the resultant race activity." Many more examples available by Google search. If you have the ATSG Upgate Handbook for the 700R4, check the 1982 changes. Here is what it says. "Beginning on May 3, 1982, a new forward sprag clutch entered production, replacing the forward roller clutch on all THM 700-R4 transmissions." So I repeat - a sprag is a sprag and a roller clutch is a roller clutch.

[@mk-xg2kt]

one more. poorly adjusted shifter

[@mountainsgarage]

Yes!

[@77camaro]

Don't forget driveshaft length.

[@mountainsgarage]

For sure!

[@littledeel]

Complete gibberish to me. Why won’t you put any of this in Laymans terms, not all of us know what you’re talking about and we’re trying to learn. This was extremely confusing are you telling us to never shut our engine off or allow it to turn off when the vehicle is moving at a high rate of speed? And if it does we’re probably going to die due to some uncontrolled explosion inside the transmission? Why can’t you do a burn out in first gear also what happens if you blow the tires off from the starting line? I’m not trying to be a dick but I really don’t understand what you’re talking about

[@codymartin879]

Why don't you look up transmissions for idiots first?

[@robertshaw5914]

1.75 playback 😊speed works great for the videos. Other w i s e it's to S L o W.