One of the last big items on my list to finish my car is the Transmission. I was planning to buy one complete but that DIY bug hit again. I've built a couple TH350's before and both had minor issues so my confidence in transmission building was a little low. But after reading all the books I could find and all the online research my eyes could bare I decided to do it myself. If anyone has any constructive criticism, I'm all ears.
I started with a TH375 that my father in law gave me. He thought it came out of one of his roundy round 70's pontiac grand prix. I didn't care if it worked because it was just a core and it was free. I just had to find a th400 output shaft and extension housing to convert it.
In the process of doing some fab on my old wh1 chassis, I needed an engine and trans for mockup. So, I swapped the output and while I had it apart, I cut it for a JW Ultrabell. It was already a BOP case, but I figured if I ever wanted to swap to an LS, sbc or bbc the trans would already be ready to go.
When I tore down the transmission to inspect it I found that the forward section of the planet had a small crack. I replaced it with a sprag type setup. It had aluminum pistons in each drum and in the center support. The rest of the parts I was going to re-use were in good shape.
I cleaned and cleaned and cleaned the case. I wanted to put it in the dishwasher, but I figured the wife wouldn't like that too much. A fresh coat of paint, new bushings, seals etc and it's ready to go. I left the rear case bushing a little high so I can do the th350 pump bearing mod.
I cleaned, installed new bushing and bearings in planets, they all had acceptable clearances. I'm waiting on a new mainshaft from Extreme Automatics as soon as he gets some other parts in for me.
I bought a "race ground" 34 element direct drum from Hutch Trans. He takes a roller clutch drum and pops the old dog race off and installs a new sprag inner race and grinds it to his own spec. He machines it for extra feed passages, a real snap ring and for a bearing between it and the forward hub. It's a nice piece. I drilled a .063" relief hole in it and loaded it up with 5 grooved borg warner clutches with .070" clearance on Hutch's reccomendation. I'm waiting on the return springs that come with the transbrake so I can finish this up.
The way he machines the new feed passages, requires that the 2nd sealing ring land on the center support be machined away to feed the new ports. While I had the center support in the lathe, I cut it in preperation for adding a new drum support/ sealing ring in the last ring land. I also machined a support/ sealing ring from a piece of teflon. Again, I can't take credit for this idea. Hutch didn't think it was necessary, but it also wouldn't hurt. I'm also using the 4L80E sealing rings and center support bushing here based on Turbobitt's suggestion.
I'm using 3 smooth 4l80e borg warner high energy clutches on the intermediate. Getting the clearance right has been a royal pain and I have a couple sets of clutches and steels here to prove it. Final clearance should be right at .040 if the last steels I ordered come in at the size they are supposed to be. I also bought a case lug support (the original) from Hutch.
The forward drum/ input shaft is something I got on trade for doing some work for a friend. I have no idea who made it, but it appears to be good. The only thing I did was polish the seal surfaces and re-coin the check ball seat. It has a solid shaft, so I've left the outermost bushing out of the stator support. I loaded it up with 5 smooth BW high energy clutches and a sonnax clutch hub. .070 clearance on this pack also.
I don't have any pictures of the pump while it was apart, but I lapped all the surfaces on my surface plate with some 300 grit paper. I installed a plug in the converter feed and drilled a .110" feed hole in it. Put a set of new gears in it with less than .002 clearance. I have a spring in it that should give 195 psi of pressure.
That's where I'm at today. I'm waiting on a griner transbrake and intermediate shaft from Extreme Automatics. Then I'll assemble it all with minimum thrust clearance at both ends.
I started with a TH375 that my father in law gave me. He thought it came out of one of his roundy round 70's pontiac grand prix. I didn't care if it worked because it was just a core and it was free. I just had to find a th400 output shaft and extension housing to convert it.
In the process of doing some fab on my old wh1 chassis, I needed an engine and trans for mockup. So, I swapped the output and while I had it apart, I cut it for a JW Ultrabell. It was already a BOP case, but I figured if I ever wanted to swap to an LS, sbc or bbc the trans would already be ready to go.
When I tore down the transmission to inspect it I found that the forward section of the planet had a small crack. I replaced it with a sprag type setup. It had aluminum pistons in each drum and in the center support. The rest of the parts I was going to re-use were in good shape.
I cleaned and cleaned and cleaned the case. I wanted to put it in the dishwasher, but I figured the wife wouldn't like that too much. A fresh coat of paint, new bushings, seals etc and it's ready to go. I left the rear case bushing a little high so I can do the th350 pump bearing mod.
I cleaned, installed new bushing and bearings in planets, they all had acceptable clearances. I'm waiting on a new mainshaft from Extreme Automatics as soon as he gets some other parts in for me.
I bought a "race ground" 34 element direct drum from Hutch Trans. He takes a roller clutch drum and pops the old dog race off and installs a new sprag inner race and grinds it to his own spec. He machines it for extra feed passages, a real snap ring and for a bearing between it and the forward hub. It's a nice piece. I drilled a .063" relief hole in it and loaded it up with 5 grooved borg warner clutches with .070" clearance on Hutch's reccomendation. I'm waiting on the return springs that come with the transbrake so I can finish this up.
The way he machines the new feed passages, requires that the 2nd sealing ring land on the center support be machined away to feed the new ports. While I had the center support in the lathe, I cut it in preperation for adding a new drum support/ sealing ring in the last ring land. I also machined a support/ sealing ring from a piece of teflon. Again, I can't take credit for this idea. Hutch didn't think it was necessary, but it also wouldn't hurt. I'm also using the 4L80E sealing rings and center support bushing here based on Turbobitt's suggestion.
I'm using 3 smooth 4l80e borg warner high energy clutches on the intermediate. Getting the clearance right has been a royal pain and I have a couple sets of clutches and steels here to prove it. Final clearance should be right at .040 if the last steels I ordered come in at the size they are supposed to be. I also bought a case lug support (the original) from Hutch.
The forward drum/ input shaft is something I got on trade for doing some work for a friend. I have no idea who made it, but it appears to be good. The only thing I did was polish the seal surfaces and re-coin the check ball seat. It has a solid shaft, so I've left the outermost bushing out of the stator support. I loaded it up with 5 smooth BW high energy clutches and a sonnax clutch hub. .070 clearance on this pack also.
I don't have any pictures of the pump while it was apart, but I lapped all the surfaces on my surface plate with some 300 grit paper. I installed a plug in the converter feed and drilled a .110" feed hole in it. Put a set of new gears in it with less than .002 clearance. I have a spring in it that should give 195 psi of pressure.
That's where I'm at today. I'm waiting on a griner transbrake and intermediate shaft from Extreme Automatics. Then I'll assemble it all with minimum thrust clearance at both ends.
