Thread: 01 gtp tranny question

I have a 01 with 155k on it and 4th gear is gone. Found a junkyard tranny but he don't know if it's a HD or out of a non SC car. Has around 100k on it. My question is what can I read on the tag to see if it's a HD tranny? If it's not how can I covert it over. I obviously know from using the search function the diff and converter need swapped but I can't find any working links that show me how to. No one rebuilds these transmissions in my area anymore. Getting it tuned for the different ratio isn't an issue and I read something about the passenger axle shaft being different which isn't a big deal. Anyone have any useful info on this subject?

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Skip the tag and measure the size of the differential cover. The HD cover is longer than the non-HD. That's the quickest way to tell. Also look at how your transmission lines connect to the trans.

If it's HD there are 37 drive teeth and 33 driven teeth so it's 1.121 ratio, Non-HD is 35 and 35 is 1.00 ratio. After those ratios the diff makes the rest of the difference. Shoot a pm to Scottydoggs or if you find a link to Dropbox from him the rebuild manual is in there.

Heres the torque converter How to install a torque converter onto the transmission
In case you need removal of a trans: How to remove a transmission

I know I've got diff removal somewhere. ... where though? You remove the bolts for the diff cover, then put a large screwdriver into the diff where the output shaft sits and give it a quick hard smack with a hammer. The circlip will release and you'll have the diff out. To reinstall slide the output shaft about 3 inches to the other end of the transmission, put diff in place and cover (if cover does not sit flush by hand there are is a bearing behind diff and parking pawl that needs to be reset (use a dab of grease to hold it in place) on. Then slide output shaft back to the diff and with a block of wood on it.. give it a smack to reseat it.

Originally Posted by BillBoost37

Skip the tag and measure the size of the differential cover. The HD cover is longer than the non-HD. That's the quickest way to tell. Also look at how your transmission lines connect to the trans.

If it's HD there are 37 drive teeth and 33 driven teeth so it's 1.121 ratio, Non-HD is 35 and 35 is 1.00 ratio. After those ratios the diff makes the rest of the difference. Shoot a pm to Scottydoggs or if you find a link to Dropbox from him the rebuild manual is in there.

Heres the torque converter How to install a torque converter onto the transmission
In case you need removal of a trans: How to remove a transmission

I know I've got diff removal somewhere. ... where though? You remove the bolts for the diff cover, then put a large screwdriver into the diff where the output shaft sits and give it a quick hard smack with a hammer. The circlip will release and you'll have the diff out. To reinstall slide the output shaft about 3 inches to the other end of the transmission, put diff in place and cover (if cover does not sit flush by hand there are is a bearing behind diff and parking pawl that needs to be reset (use a dab of grease to hold it in place) on. Then slide output shaft back to the diff and with a block of wood on it.. give it a smack to reseat it.

All great info Bill. Trans works great aside of the 4th gear being shot would it be worth replacing the 4th gear hub? I have no 1811 code or any other codes just no 4th gear? Worth it?

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Originally Posted by dazedandconfused

...would it be worth replacing the 4th gear hub? I have no 1811 code or any other codes just no 4th gear? Worth it?

If you are mechanically inclined, I would say yes. It would also be a great time to instal a shift kit. Having the side cover off gives you access to the part of the kit that usually get left out. 2 birds, one stone.

I've done it .. Brandon's done it. You could.l

Ok planning on doing the 4th gear hub, along with a shift kit. Gunna kill 2 birds with one stone and do my headers while the cradle is lowered. On that note, would it be benificial to pull the trans out all the way to do the 4th hub or not? And do I need any other parts besides the 4th hub?

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Originally Posted by BrandonHall10

If you are mechanically inclined, I would say yes. It would also be a great time to instal a shift kit. Having the side cover off gives you access to the part of the kit that usually get left out. 2 birds, one stone.

What part is that?

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It's been a looong time since I had those instructions in my hands. I want to say the 3-4 accumulator.

I think that's the right name.

Originally Posted by dazedandconfused

Ok planning on doing the 4th gear hub, along with a shift kit. Gunna kill 2 birds with one stone and do my headers while the cradle is lowered. On that note, would it be benificial to pull the trans out all the way to do the 4th hub or not? And do I need any other parts besides the 4th hub?

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Anymore input on this? Would doing a gemini chain be a good idea too? Or will clutches and/input shaft give problems before the drive chain?

Goal is to run a 3.4 pulley when the dust settles so would a shift kit and gemini chain hold up for awhile driven fairly conservatively?

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Thanks to all who partiticipated in this thread. Finally got the 4th gear hub in and fixed my car. Took me about 10 hours altogether. Only slight hiccup I had was that I missed unbolting the rack and pinion from the cradle when I lowered it so I I pulled the intermediate steering shaft apart [emoji23] but that was a simple enough fix and it's all back together. With the writeup on here and a good YouTube tutorial it wasn't too bad. I know these cars are a dead platform, but I enjoy doing this sort of work. A transmission shop quoted me a price of over $1,500 to do it and I had around $100 in it including the hub, fluid, and a shift kit/filter.

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That's awesome. Hey, new cars are nice, but not having a car payment is pretty cool too.

There's a certain amount of confidence that comes with knowing you can fix your own junk if/when it breaks.

You got that right Brandon. Although I find if I fix something here and there whether it's home, car or who knows related, I find it's a great feeling knowing I was able to save a good chunk of cash in the process.

Originally Posted by BrandonHall10

That's awesome. Hey, new cars are nice, but not having a car payment is pretty cool too.

There's a certain amount of confidence that comes with knowing you can fix your own junk if/when it breaks.

I could have any car I want pretty much, but I like bringing a car back to life. When I got this one, 4th was gone, had the water in the floor boards issue, ps pump leaked, crank seal was leaking, but I paid $800 for it and knew about most of its issues beforehand. It's not a daily driver so I have time to work on it. My kids call it dad's racecar [emoji23] boy do I have them fooled. So far, I've fixed brake lines and the above listed issues, put a 180* t Stat, open cone filter, tuned it, headers, and a mps on it, with the shift kit. Hoping to get into the 12's this summer without intercooler or opening the engine. Perhaps with switching to E85 that might be possible. Maybe it's a pipe dream, who knows. If that doesn't get me there a 75 shot surely will [emoji23]

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The hoopty as I affectionately refer to it as

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