A little more help please. I cleaned off the tranny id tag and found the following codes. PV 69 59587. I don't see this code in the GTO Restoration guide and could not find any info on-line. I am assuming that there was a tranny change by a previous owner. Can you help me id this tranny and let me know if you think I should find an period/car correct tranny. Planning a stock rebuild (except for a 30 over bore) on the 400 350 HP YS block with. The block is not numbers matching but is correct for the period/car.
Assume Turbo Hydra-Matic 400? Can't help you on the ID tag, but it should not make any difference what year or what maker the trans came from. The TH-400 that fits your car also fits Buick & Olds. So as your block is not numbers matching, trans should not be that critical or matter -my opinion.
Tip, the GTO TH-400 was beefed up from the factory. Many had the His/Hers flood shifter (yours?). This allowed the transmission to be placed in "D" for normal shifting via automatic shift points. Slide the shifter over to the 1-2-3 quadrant and it becomes a manual shifting automatic. It will hold in whatever gear you place it into and will not
shift until you shift it. You control your up & down shifts. The transmission also has a higher line pressure so you get firm shifts. I had a '68 with the His/Hers that I used to wind out with the old G-78 tires and non-posi and catch a very audible 1-2 tire chirp. The firmer/higher line pressure is actually a good thing because there is little to no slip from the clutches, so they last longer.
To get this correct go to TransGo
Click on "General Motors"
Click on "THM 400, 3L80"
Click on "400-1&2"
This is the shift kit you want to use. It can be "programmed" using certain springs/check balls to give you different settings. You want the "street" setting. "Competition" setting is a real slam-bang shift - you don't want this.
You can do a search to get your best pricing on this kit if you choose to use it. I used one in my brother's Plymouth 904 trans and it did what it said.
You will also install a new torque converter when you rebuild your trans. You want to make sure you get a converter for a Pontiac engine and not a Chevy as a Chevy converter may have a higher stall RPM when used behind the torque of a Pontiac engine. The Pontiac factory stall is 1800-2000 RPM's. If you get a Chevy converter, you may find it going higher to around 2,200RPM or so. Many converters from many manufacturers and suppliers. Just do some research and question asking.
Check out Cliff Ruggles website. He has a couple books on the TH-400 and swapping in a late model overdrive trans. From what I gather, Cliff Ruggles is a supplier of Continental Converters which are designed for Pontiac applications. You can actually contact/call him to get a better idea and perhaps a price. The only experience I have had with aftermarket torque converters was with my brothers 360CI Plymouth build. I got a torque converter from Edge Racing Converters. The guy will contact you for all your car info and build a torque converter to meet your cars needs. I got a "tight" torque converter with a 2,500 RPM stall and was real pleased with it. It did what it was supposed to do. Very little slip so it was like a stock converter until you nailed the gas -then it got up and went. So they may be able to help. Very reasonable pricing -and I'm cheap. LOL.
I found this tip on another blog on correctly installing a torque converter. Never had a problem with a stock converter, but aftermarket converters are not always as "stock". ------ Just to clear up a possible misconception on the measurement. What they say is to not run the combination with the converter pushed into trans. When you set things up, you do fully seat the converter completely as far back as it can go into the trans. After installing the trans, a perfect distance would be 1/8" from the converter tangs to the flexplate with the converter still all the way back. Then you would simply pull the converter forward against the flexplate and bolt things up. If the distance is not 1/8", but greater, then you need to use hardened flat washers between the flex plate and torque converter tangs to reduce the total distance/gap down to 1/8" before installing your bolts and tightening it up. Too much distance and there is a possibility of pulling the converter out of the pump, or at least not having enough contact area. If you use additional washers, you will need a corresponding longer attaching bolt. Also use blue loctite on the bolt threads during assembly.
It appears the Continental Converters are not tapped for bolts, but the holes are drilled - so you need to ask if you go with one. "We use, and highly recommend, 7/16" grade 8 bolts with nuts (fine thread) for holding the 10" Continental torque converters in place. Make sure to use hardened washers as well, as a soft washer isn't a good idea when used where you are counting on the torque applied to the fastener to keep it from loosening up......Cliff