Removing the Transmission 1969 GTO - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 10-02-2014, 10:50 AM Thread Starter
 
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Removing the Transmission 1969 GTO

I am in the process of dropping the automatic transmission on my 1969 GTO Convertible restoration project. I have disconnected the shift linkage, the cooling lines, and electrical. I removed the cross-member and the three bolts that hold the torque converter to the flex plate. The torque converter turns easily by hand. Last night I supported the trans with jacks and removed the 6 transmission bolts. I raised and lowered the transmission with the jack to try to break the transmission loose from the engine block but it seems to be stuck. I went back over each step to make sure I disconnected and removed all bolts and anything else that may be keeping it from breaking loose. I also put PB Blaster on the aluminum pilot tabs to make sure they are loose. Did I miss something or is there a trick to getting the transmission to break loose from the block?
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post #2 of 10 (permalink) Old 10-02-2014, 12:42 PM
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Make sure you also support the rear of the block before you try to separate them. In the car, the two motor mounts and the rear transmission point are the only 3 points that support the combined weight of the engine and transmission. If you DO manage to get the transmission separated without having the rear of the engine supported, you're going to have a very bad day. The engine is going to rotate and fall backwards, probably ripping both motor mounts loose --- additional mayhem will ensue.

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post #3 of 10 (permalink) Old 10-02-2014, 01:58 PM Thread Starter
 
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Thanks Bear. I will get a jack or jackstand under the block and try to lower the transmission this evening. I did notice that when I lowered the transmission last night that the engine dropped a bit.
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post #4 of 10 (permalink) Old 10-02-2014, 06:30 PM
 
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Make sure the brace on the starter is free, if you have one. Double check that you have ALL bolts out on the bellhousing as I think I have done this and found one that was a little hidden/hard to see. Look at the drawing I posted. If you know you have all the bolts out, it might just be stuck on the alignment dowel pins found in the block -the big holes you see on each side of the bell between the bolt holes. This is common as over time corrosion can make them stick. Get your engine supported as Bear said, I think I have actually placed a block of wood in between the back of the head and firewall.

Make sure your trans jack is not pressuring the trans upward, you want to have some weight of the trans to help drop/separate it from the engine. To separate the bell from the block you may need a screw driver, a thin one at first (or even a well place putty knife as long as you can tap it with a hammer), placed at the parting line and give it a few taps with a hammer to wedge it in. If it does not separate somewhat and remains "tight", you still may have missed something. Try one side then the other. You should be able to get some separation, but don't force anything as you don't want to crack/break the bellhousing.

If you see some separation, ie the screw driver is slipping in, then do the same on the other side. Go a little on each side so as to put even leverage on each side -your alignment pins are sticking. You should see the gap widen on each side, you can step up to a larger screw driver if it appears to be separating and just work side to side. Get ready for it to drop/pull out when the gap gets about 1/4" to 1/2" alll the way around-as I recall. That should do it.
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post #5 of 10 (permalink) Old 10-03-2014, 05:28 PM Thread Starter
 
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Bear and Jim, Thanks so much for the advise. I was able to drop the tranny in about 15 minutes this evening after I propped up the engine and used the screwdriver technique. You guys are great and I sincerely appreciate your help.
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post #6 of 10 (permalink) Old 10-04-2014, 12:41 PM
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Bear, I've never seen that happen, and I've been doing this for over 35 years.
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post #7 of 10 (permalink) Old 10-04-2014, 03:38 PM
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Originally Posted by Rukee View Post
Bear, I've never seen that happen, and I've been doing this for over 35 years.
I've never seen it either - nor do I WANT to

It just stands to reason that having the engine hanging like that on the mounts is going to put some hurt on that rubber, even if they don't tear loose.

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post #8 of 10 (permalink) Old 10-04-2014, 08:07 PM
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I haven't seen it happen, either. But it's good practice to support the engine so that it doesn't tip back and pinch the engine and trans joint tight....and make for a bad situation that needs to be dealt with....lying on your back with trans fluid pouring on your chest from the converter. Easier to support the engine and do it surgically, without the drama. JMHO.....
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post #9 of 10 (permalink) Old 10-09-2014, 08:50 AM Thread Starter
 
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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.
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Originally Posted by gtogoober View Post
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
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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