Hitman's Pontiac Trans Am Forum

Trans Am Information => Trans Am Tech => DriveTrain => Topic started by: Sir english firebird on November 15, 2009, 11:50:32 AM

Title: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 15, 2009, 11:50:32 AM
Ok i had a looky through the forum and couldnt find what i was looking for so its time to post.

I want to rebuild my poor ol tired TH slushbox, im pretty sure its a 350 but to be honest i cant be sure as the previous owners where less than kind to my poor ol Bird.

Its needed a new box ever since ive had it, but time and funds just never seem to be together , but the old box plodded on and put up with the grief.

Now its really had enough, ive had a looky at rebuild kits and was wondering if anyone had built their own or has any usefull advice.

Yes i could buy a recon box here (UK ), but the prices are just sky high and as for a new one, well the only way to go would be to get one there ( US ) and have it shipped and then im talking again.

Thanks guys, i took the poor old girl out for a spin today and it made me realise just how bad it is.......  :'(
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: RENOVATIONS on November 17, 2009, 08:22:30 AM
I'm no help on that but you might check with ih8z28s (Joe)...I recalll he rebuilt his own trans in the past ;)
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: kjkjkcjkcj on November 17, 2009, 08:39:22 AM
If you do I siggest taking lltons of photos. I could only imagine
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: SoonerTA on November 17, 2009, 11:19:32 AM
I have seen step by step videos online.  I will try and find them again.  I think it would help a lot. 
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 17, 2009, 12:34:18 PM
Cheers guys, i have bought a " rebuild and uprate " book off Ebay, i was lucky as its the only one ive seen over here.

When i do get my finger out ill shoot pics etc, but it wont be for a while yet, i havent even pulled the transmission yet!
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: deadfish on November 17, 2009, 02:27:43 PM
Did mine years ago using a "B&M Transkit" and a manual I found through a parts supplier. You will need a few special tools to compress springs but I made them as I needed them...not too difficult if you're a bit inventive. It is also VERY important to keep everything extremely clean as there are small screen filters here and there that will clog easily...even lint free shop rags. To get it all back together in the proper order, as each part was removed and cleaned, I'ld put it in a wax paper sandwhich bag marked with a label and strung them along a wire with clothespins, then when it came time to reassemble, I simply started from the far end of the wire and replaced the parts in reverse order. The case was sent to a tranny shop to be hot tanked. I also bought the low/reverse clutches and steels and a "case saver" from the shop. Those parts were not included in the "Transkit". Anyway it can be done more easily than you might think..heck...mine still works!
Good luck and keep us posted!

Rick C.
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: turbota400 on November 17, 2009, 05:17:39 PM
I also rebuilt mine.  I agree, keep the parts on order as you take them apart and keep them CLEAN.  Any little bit of debris could plug things up or scar the clutch plates.
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 17, 2009, 06:16:09 PM
Rick and Shawn thankyou, i appreciate what youre saying, as for tools, well im pretty inventive but well see, its a little way off yet, i need to source the " kit " to do the job.

Thanks, i dont know if im looking forward to it or not but im most certainly going to have a go..... whats the worst that could happen? 3 reverse gears perhaps? LOL
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: deadfish on November 18, 2009, 06:33:20 AM
Rick and Shawn thankyou, i appreciate what youre saying, as for tools, well im pretty inventive but well see, its a little way off yet, i need to source the " kit " to do the job.

Thanks, i dont know if im looking forward to it or not but im most certainly going to have a go..... whats the worst that could happen? 3 reverse gears perhaps? LOL

Your welcome...LOL three reverse gears? no problem!...just move the steering wheel to the back seat!

I got my kit from "Jegs". Summit also used to carry them. (Jegs was less money at the time...1991?)
Seriously...it really is easier than you might think...hardest part is taking it out and putting it back in!

Rick c.
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 18, 2009, 10:27:21 AM
I think the 3 reverse gears will probably be the least of my worries! PMSL

Ill check into Jegs etc, thankyou again for the heads up!

Much appreciated from over here!
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: SoonerTA on November 18, 2009, 05:10:10 PM
Rick and Shawn thankyou, i appreciate what youre saying, as for tools, well im pretty inventive but well see, its a little way off yet, i need to source the " kit " to do the job.

Thanks, i dont know if im looking forward to it or not but im most certainly going to have a go..... whats the worst that could happen? 3 reverse gears perhaps? LOL

Your welcome...LOL three reverse gears? no problem!...just move the steering wheel to the back seat!

I got my kit from "Jegs". Summit also used to carry them. (Jegs was less money at the time...1991?)
Seriously...it really is easier than you might think...hardest part is taking it out and putting it back in!

Rick c.


What kit did you get?  Did you also install a shift kit?
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: deadfish on November 18, 2009, 07:14:30 PM
I believe it was called "Transkit" or "Transpak" put out by B & M. One is just the shift kit (reroutes fluid in the valvebody) The other is the whole thing and includes the shift kit) (minus the low/reverse clutches and steels for some reason) At the time, they were the only two available from them...(can't remember exactly which was which or if I got the names perfect...I did this in like 1991)

Rick C.

ps.. Oh yeah..I did install the shift kit...utilizes the whole low/reverse piston (stepped piston) in either shift position. Normally only one step section received fluid in each position...makes for a better launch!
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Chobby68455 on November 21, 2009, 02:29:52 AM
Hey i did a TH350 and TH400 in auto trans class(college) what i did was take pictures of how the parts looked inside the transmission. Also be vary careful on the valve body. The little check balls are gonna want to fall out and u dont want to spend ur time looking for them when for some reason they seem to dissapear when they land on the floor. And make good note or take a picture on where they go. O and keep your snap rings in order because i noticed there are two(if i remember correctly) snap rings that are almost identical but actually a little different from each other. Thats if i remember correctly. Im not a master transmission mechanic hence im still learning and in college but, these are some things that might help. Have fun!
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 21, 2009, 10:16:25 AM
Unfortunatley my college was too long ago and we only messed with Europeans!

I think this is going to be a labour of love, i appreciate the comments and theres alot of good advice........ i could always fly it over as "hand baggage" PMSL
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Chobby68455 on November 21, 2009, 01:37:48 PM
hahaha well thats what happens if u live in england. Actually i also own a jetta and man can i tell u the parts are expensive. if i could have only kept that money used in german parts and used it for american parts for my bird.....it be running mid 12s by now hahaha
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: pat on November 21, 2009, 03:21:51 PM
take lots of pics i want to try this too at some point
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: RRR76TA on November 21, 2009, 03:47:55 PM
You can do it
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: chets78TA on November 22, 2009, 02:03:16 AM
The TH350 is the easiest trans I have rebuilt. I've done 5 of them so far and they are all still going. I attached a link for transmissionpartsusa.com which is were I buy most of my parts. they have the best prices around. I'm not sure if they will ship to the UK but it's worth a shot. There is a book out called "Turbo-Hydro Matic 350 handbook" which is VERY good. I highly recomend it as it provides step by step instructions with lots of pictures. It also has performance and trouble shooting chapters. I agree with the others about a clean area and special tools. I made my spring compressor from threaded rod & angle iron 12 years ago and it's worked every time. Give it a shot.  If you have questions or run into trouble give a shout.

http://www.transmissionpartsusa.com/Default.asp (http://www.transmissionpartsusa.com/Default.asp)
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: RENOVATIONS on November 22, 2009, 11:04:17 AM
Found this link that might help a bit Steve:

http://www.nastyz28.com/forum/showthread.php?t=53671
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: Sir english firebird on November 22, 2009, 12:44:52 PM
hahaha well thats what happens if u live in england. Actually i also own a jetta and man can i tell u the parts are expensive. if i could have only kept that money used in german parts and used it for american parts for my bird.....it be running mid 12s by now hahaha

A Jetta??? omg lol
Do you need parts? is it cheaper to buy them here?
As for living in England....... it wasnt my fault where i was born.... but we do have fish n chips and proper pubs! etc etc and MINI's eh Rick!

As for the help guys, i cant tell you how much i appreciate it, im hoping to move workshops soon ( to get more space ) so if work doesnt get too busy the Bird will get a makeover!

Jeff thanks for the link, ive added it to my faves. ( ps wheres your bloody passport? )
Title: Re: "TH" gearbox rebuild, has anyone done it themselves?
Post by: ih8z28s on November 22, 2009, 05:51:33 PM
I rebuilt my TH350 last summer, I was a little intimidated at first, but once I got into it it was actually pretty simple.  I completly disassemble it and took the torque converter and a few parts to a local shop.  I had them flush the converter and run the case through their machine to clean it.  Then I had them install any bearings that needed replacing.  I assembled the rest.  I bought my kit from Northern auto along with a shift kit.  I cannot stress enough that a good manual and torque wrench are needed  during the process.  I took a bunch of pictures, but don't know where I have them.