4. GM TH400 Rebuild: Gear Train Assembly and Installation

I rebuild the gear train, check travel between the front and rear planet, then install the assembled gear train into the case and check rear end play.

[@nv1493]

Years later your th400 builds continue to be extremely helpful. I'm working on my first one, using ATSG manual, doing stuff like dual feed, 4L80e direct drum w 34 element sprag, rollerized output, the list goes on for a durable dependable unit. The clear instruction and details you give will help make this a success. All I have to do is pay attention and work to specs. THANK YOU.

[@nickstransmissions]

Great to hear, NV! Thank you for watching!

[@nickkiofetzis5667]

that's some pretty awsome video and thanks heaps for the intresting knowledge and great footage, you are currently number one in t400 rebuilds in my books thanks heaps cheers nick

[@nickstransmissions]

Thanks, Nick! I appreciate it.

[@johnnybriggs2090]

Nice work nick.

[@nickstransmissions]

Thanks, Johnny!

[@inscoredbz]

Was those shims for the rear planetaries the sonnax shim kit they make? Where can you get the selectives for the rear planetaries and the forward hub? Can you get them in metal instead of plastic? For a performance build, i prefer metal thrust washers, but is plastic just as good or better? What should the clearances be for the forward hub? Does anyone make shims for it as well? Your the man Nick! There's a heck of a lot of great information in this video that nobody shows.. That is the best i have seen on setting up endplay for the rear planetaries and forward hub. I appreciate it very much. one more question if you don't mind. You said in the pump video that the cover was new and also fit an Allison transmission. Did they update the converter feed hole to reduce thrust on the converter? Where can one of those pump bodies be bought from? Thanks again.

[@nickstransmissions]

Thanks, Nitroman. Shims are for/from setting backlash for a GM 12 bolt Truck differential carrier (they go underneath the carrier bearings) and can be bought online or local driveline shops. You can also buy the Sonnax shims. No measurements for travel, it’s all by eye and feel, as explained in the video. Pump body doesn’t have the TC charge port, that’s in the pump cover and should be restricted if a high pressure PR spring is used so you avoid ballooning the converter. Those pump bodies are available from Transtar.

[@inscoredbz]

@@nickstransmissions your right about the converter charge port, I was backwards thinking on that. I'll have to look for those shims. What about the smaller selective for the forward hub? I haven't seen those offered as selectives.

[@nickstransmissions]

Google; not sure where i got them. Some may have come with billet forward hubs

[@ronselberg4704]

Hi Nick, I know this is an older video. Some comments on shimming under the 4 tang washer to reduce slop in the upper planetary movement. Did the same test on mine and ended up with a .045" shim. Then realized I had not installed the plastic washer up inside of the bottom of the center support. I didn't see you install it in your video either? Anyway, after installing the plastic washer, I had to reduce the shims under the 4 tang to .015". I used the same shims from a 12 bolt installation kit. Without relief grinding the shim where it resides inside the tangs, the shim didn't fit flat. Probably some variation on the OD depending on the shim kit.

[@nickstransmissions]

Hi Ron, thank you for watching...That center support rear-side washer is on there, I just may have not have shown it (can't remember) but you don't want to omit it. Sometimes you don't need to shim the rear planet as the travel between it and the front planet is acceptable as-is, but sometimes you do.

[@ronselberg4704]

Appreciate the response Nick. Very informative, and you are right, not a common check. I'm not a trans guy, just a drag racer who has done all my own TH400's. Mid 8 sec belly button turbo Nova. Adding the HD shafts, 36 element sprag etc and finally a trans brake. Should be interesting.

[@nickstransmissions]

You're welcome, Ron. Yep, for sure sounds like a neat build...let me know how it turns out or if you have any other questions.

[@jordansmith8467]

How wide and deep is your channel in your assembly stand? Just curious and looks like a wonderful tool to make! ☺️

[@keysautorepair6038]

I seriously don't know how anyone makes money building transmissions it takes 17 hours to clean them prep and assemble you definitely earn every penny.

[@nickstransmissions]

There’s still a relative scarcity between supply (ie reputable, competent transmission builders and demand for their services so that’s keeping the segment going…Equipment like hot tanks, solvent washers, sonic cleaners etc speed up the cleaning process so getting all the individual parts clean for a given unit only takes an hour or so and assembly is usually only a couple hours once your versed on a given model of transmission. For example, Im into a 4L60e between 4-6 hours depending….But like anything else, you have to make the investment in equipment to make it efficient and be willing to wait a while before your revenues offset all that outlay. In short, you’re paying one way or another (time or or money, two sides of the same coin).

[@keysautorepair6038]

@@nickstransmissions I would say you would have to be a dedicated transmission builder to make any money and people don't want to pay for anything anymore they want cheap.

[@nickstransmissions]

@@keysautorepair6038 trans work is all I do for the general public and no arguments from me.

[@donaldbrinkman8209]

Great video,where did you get the shims used to adjust the drum clearance? I'm doing a 400 right now and need to shim for proper clearance.

[@nickstransmissions]

Thanks, Donald. I believe those particular shims are from a GM 12 Bolt Truck differential bearing shim kit used to set/adjust ring gear backlash. They can be found online or at most driveline shops.

[@donaldbrinkman8209]

@@nickstransmissions Thank's for the quick reply 👍

[@jordansmith8467]

Very interested in making the stand you are using here in the video holding the planets. Amazing idea. Looks like a 8"x8" 3/8" plate steel top but how bid is your opening and depth? If it's a trademark secret, I understand but would love to make a similar unit as I'm a newer th400 builder myself.thank you kindly and have a good day

[@nickstransmissions]

Assuming you're referring to the first portion of the video, the stand is actually just my foot press. Those are available on-line and through some transmission parts suppliers. Price-wise, they range from a few hundred to $1000+ depending on who makes it and where it's made (USA-made presses are typically much more expensive). If you only anticipate doing one to a few transmissions per year, you can buy vice-mounted units that compress return spring assemblies that are much cheaper. But if you plan on building transmissions more frequently, I'd spend the money on a good foot press.

[@ijteague]

Does the sun shaft and sun gear weep hole alignment depend on the type or year of sun shaft? My sun shaft is grooved 360 in which case I would imagine the fluid will fill up the channel and weep out regardless of its position.

[@nickstransmissions]

The lube port in the sun gear shaft must align with the lube port on the sun gear (they are lube ports, not weep holes). The beveled splines on the sun gear must face down (ie rearward) when installed.

[@designsinorbit]

Hello there...thanks for the great video. I have a quick question for ya- I'm attempting to reassemble my TH400 and I am getting conflicting information online regarding the rear case thrust bearing. My transmission currently has a thrust bearing (the kind that is just a washer with 3 tabs and no actual bearings) but I'm not sure if I should be upgrading this. My goal is trying to upgrade as much as possible to keep up with the added horsies. I'm at 575hp up from 250hp. Anyhow, if you can shed any light I'd surely appreciate it. I wish I could hire you as a consultant from afar because I REALLY don't want to mess this up.

[@nickstransmissions]

Hi Designs in Orbit...Rollerizing is easy..just swap the three-tab steel washer and babbit style washer on the back of the output shaft for a TH350 pump thrust bearing and appropriate amount of shims to get your rear end play to about .006-.012. Here's my video where I walk you through the process: kzbin.info/www/bejne/jaXNmaB8ep11frc

[@jordansmith8467]

I've stacked up my gear train 5 times now and have zero play. What am I doing wrong? I follow you and mr mountain

[@nickstransmissions]

Hi Jordan, impossible to say without being there to watch what you're doing but my guess is that you aren't doing anything wrong...stack it up with no four-tab thrust washer on the rear planet and see if you have space between them. If you still dont have any something is wrong...Are you working with all of the origional gear train parts or were one or more parts replaced?

[@jordansmith8467]

All original parts in amazing shape. Just at a loss here. Even atsg shows me doing it right

[@nickstransmissions]

@jordansmith8467 yea stack it up without the washer and see if you have spacing between them, and if so about how much...should feel like about the thickness (or slightly more) of that washer on the rear planet in terms of spacing...

[@designsinorbit]

Hey Nick... it's been awhile since I reached out with any questions. I'm hoping I still have one token left. 😊 So my downshift solenoid started leaking so profusely that I had to drain it. I ordered a new one and before I install it, do you have suggestions on how I can not have this issue again? It does look like the new solenoid has a slightly wider rubber seal. The case seems fine. Nice and smooth hole. Do you ever use more than just a seal? Thanks man. Appreciate anything you can give.

[@nickstransmissions]

Hi DinO - your new solenoid shouldn't leak as long as you lube up the o-ring seal and bore thoroughly. If it still leaks then that bore is excessively worn where you'll need either a different o-ring, RTV or a different case.

[@designsinorbit]

@@nickstransmissions Alrighty, I'll do it. Thanks for your time man.

[@johnnybrigham8754]

What thread locker number did you use for the install of the 3/8 cup plugs thanks jb.

[@nickstransmissions]

Locktite 262

[@johnnybrigham8754]

@@nickstransmissions your red foot press is by who thank you.

[@nickstransmissions]

No idea as I purchased it a while back from a trans shop that was going out of business. There's no manufacturer's name anywhere on it. You can buy one identical to it on Amazon or eBay.

[@johnnybrigham8154]

Hi were can I get some of 3/8 cup plugs for the dual reverse thank you jb.

[@nickstransmissions]

You should be able to source them on Ebay or Amazon

[@johnnybrigham8154]

@@nickstransmissions nope I've been to napa advance ect can you help me out thank you.

[@nickstransmissions]

Hmmm…i just did a search on ebay, google and amazon and couldn’t find any in stock either. I bought a box of them a few years ago and haven’t had to source any since so not sure when they became scarce. Perhaps you can use a 3/8x16 set screw. Just run a 3/8x16 tap through the reverse feed passage port on the case then once the center support is installed for the final time, put some thread sealent on the set screw threads and screw it in. Alternatively you can plug the corresponding feed hole location on the separator plate though ive never done it that way so can’t tell you how to go about it.

[@johnnybrigham8154]

@@nickstransmissions anyway to get like 4 of them sent to me thank you john brigham 241 west hill rd apt15a newington ct 06111 thank you I just subscribe to your channel nice work thank you.

[@johnnybrigham8154]

@@nickstransmissions hi if you would save me I would like 4 3/8 cup plugs send you be a life saver and greatly appreciated thank you Johnny brigham 241 west hill rd unit15 a newington ct 06111