# TH400 Leak Problem



## Getyourgoat (Jul 1, 2014)

Thanks to anyone who can help.
I have a 1967 GTO with a 1972 455 & a GM TH-400 Transmission.
I have a slow trans fluid leak that according to my research, appears to be coming from either the front pump or the converter seal. I could use some tips on replacing both.

1. If I have the transmission on a transmission jack and lowered can the converter seal be changed by an average DIY'er or do I need to completely remove the transmission?
2. Same question about the pump seal. Can it be changed without removal?
3. Do I need any special tools for changing converter or pump seals?


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## Goat Roper (Oct 28, 2014)

1. You need to pull the tranny and torque converter as one unit, unbolt the converter from the flexplate 3 bolts.
2. No, the pump seal is an O-Ring.
3. Yes, you need T bolts to pull the pump you can remove the converter seal from the outside with a gasket scraper and hammer, do not use a hook puller if you do you will score the bushing for the converter and it will need to be replaced.
Also the bolts that hold the pump in have compression washers so those will need to be replaced so it doesn't leak at the bolts.
You will need a torque wrench for these bolts, some tranny lube for the O-Ring and the torque converter needs to be indexed.

If you have never done this you would be better off pulling the tranny and converter and taking it to a tranny shop or the car to them and let them do the whole job.
Find a reputable shop in your area and stay away from AAMCO.


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## Getyourgoat (Jul 1, 2014)

So it's more than a year later since my last post and I finally decided to pull the whole transmission out and take it to my transmission guy for repair. I've pulled this out once before about 28 years ago for a rebuild and could use a refresher course on removing an automatic transmission. Any pointers welcomed. As I recall, you have to get the car up in the air as far as a standard set of jack stands will reach, then remove the pan and dump the fluid followed by removing oil lines, shifter linkage, speedometer cable, fly wheel cover and dip stick tube. Next remove the drive shaft and then place a tranny jack under the transmission followed by cross member removal. Next remove all the bell housing bolts and then drop it to the ground and pull her out from underneath the car. Have I missed any thing here? And does anyone know the torque specs for the bell housing bolts?


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## Goat Roper (Oct 28, 2014)

Unbolt the torque converter from the flex plate is all you missed.
Converter to flex plate 35 pounds
Bell to block 40 pounds

Print this and put it in your manual.
Wallace Racing - Pontiac Bolt Torque Values


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## Getyourgoat (Jul 1, 2014)

I knew I was forgetting something. Awesome information! Thanks for the reply Goat Roper.


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## Goat Roper (Oct 28, 2014)

You're welcome.


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## Getyourgoat (Jul 1, 2014)

So I got my transmission fixed. I'm installing it today. My transmission guy said to make sure the torque convertor is properly seated back far enough that you can not stick your fingers between the convertor and the bell housing. So, once I have the transmission bolted in, I have about a 1/4" gap between the flywheel and the torque convertor bolt holes. I wondering if I should use shims. If I bolt it up without shims, it will pull the torque converter forward to the point where I can get my fingers between the convertor and bell housing. Should I install shims or just bolt it up and forget it. As far as I know, my convertor bolts are original and if I use shims, I will need to buy longer bolts. Should I shim or just bolt it up and forget it? 








This is what it looks like bolted in place. Notice the gap between the convertor and the bell housing. Is this OK?


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## Goat Roper (Oct 28, 2014)

Yup, I think what he was talking about was to make sure the converter was indexed before installing.
If it wasn't you wouldn't have been able to bolt the bell to the block.


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## PontiacJim (Dec 29, 2012)

Goat Roper said:


> Yup, I think what he was talking about was to make sure the converter was indexed before installing.
> If it wasn't you wouldn't have been able to bolt the bell to the block.



X2 :thumbsup: Bolt it up.


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## Getyourgoat (Jul 1, 2014)

Thanks for the reply guys. 
I saw this video on youtube... 



 and afterward I was thinking that if the convertor were to come forward it could cause premature damage to the pump. Then I saw this video... 



 talking about installing spacers if the gap were to wide. I'm confused as to which way to go. As far as I know, my TH400 was factory installed on my 455 and since I don't believe it ever had any spacers installed from the factory, I guess I will bolt it up without adding spacers and hope I don't ruin the pump or anything else in the short or long run.


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## PontiacJim (Dec 29, 2012)

Well, from what I read on the internet, 1/8" minimun to 1/4" maximum on the gap with 3/16" being ideal.

You don't have the flexplate on backwards? Silly question, but had to ask.

I know that some Pontiac's I have pulled apart did have a thin circular shim between the crank flange and flexplate. This may have been to compensate the needed distance between the torque converter and flex plate (?). Here is a blog that mentions the shim: which side of the flex plate does the washer go on? - Hot Rod Forum : Hotrodders Bulletin Board

Keep in mind that you need play as the crank does move forward/backward. If you don't feel comfortable with the gap, call a transmission shop and ask their recommendations. Or add a 1/8" hardened washer to get you to the 3/16" gap. You may need to also get longer Grade 8 bolts to compensate for the thicker shim.


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## Goat Roper (Oct 28, 2014)

Getyourgoat said:


> Thanks for the reply guys.
> I saw this video on youtube...talking about installing spacers if the gap were to wide. I'm confused as to which way to go. As far as I know, my TH400 was factory installed on my 455 and since I don't believe it ever had any spacers installed from the factory, I guess I will bolt it up without adding spacers and hope I don't ruin the pump or anything else in the short or long run.


You are over thinking it, bolt it up and run it like you stole it.
I don't think you can bolt the flexplate on backwards but look at it, the perches for the converter (raised part) should be facing the converter.
On the 400 crank there is a shim, curved edge toward the block, flex plate then the bolt plate.
There is a notch in the bolt plate for the pin on the flex plate that faces the converter so you would have to be working at it to put it together backwards.


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## geeteeohguy (Feb 2, 2008)

The TH400 in my '67 had at least 1/4" gap. I just pulled the TC to the flexplate with the stock bolts and no washers. Been like that for the past 5 years and 10,000 miles... no issue. It's when you DON'T have any gap you need to worry.


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## Getyourgoat (Jul 1, 2014)

I bolted it up as is and it runs great. One problem though, the shifter does not go all the way in to park position.
I backed out of the garage I placed it in park. My driveway is on a slope. I got out of the car to move one of my wife’s flower pots when I heard something clicking.
I turned around to see my car rolling backwards down the driveway! Luckily, I was able to jump in in time to hit the brake. What a fright! Geez O’ Pete! So now I have to figure out what has the linkage jacked up. Any adjustment tips welcome.


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## Getyourgoat (Jul 1, 2014)

I don't see any adjustments on the shifter cable unless I have to pull out the floor console. It doesn't seem to want to go in to park all the way and it doesn't seem to want to go into first gear all the way either. Does anyone know the correct procedure for adjusting this thing? Am I missing something here?


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## chuckha62 (Apr 5, 2010)

What you heard clicking was the Park Pawl trying to engage. If you can't adjust your cable, you may have to pull the trans. pan and adjust the pawl rod length. It attaches to the Detent plate/lever (aka Rooster comb) and has an adjustment at the Pawl end. However, If it was working before and you didn't adjust it while you had it out, there's no reason for it to have moved.


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## Getyourgoat (Jul 1, 2014)

Yes it did work fine before I pulled the transmission. I Feel confident that the issues in the Cable adjustment, not quite sure how to make the adjustment. I am wondering if I pull the console up that there may be some adjustment inside the shifter. I was thinking about buying a book called the GTO restoration guide thinking that it may have details on adjusting the shifter. Anyone have the book and know if it has the information I need?


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