Rebuilt TH400 problems. No park and leaking

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Old July 28th, 2014 | 06:35 AM
  #1  
Arrowstorm's Avatar
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Rebuilt TH400 problems. No park and leaking

So I recently had the transmission in my Vista Cruiser rebuilt. We took it out and took it to the shop.

When we got it back, it went in just fine. We got it shifting and running just fine.

Except that there is no park. I first noticed it when I parked on an incline and realized that the car was rolling backwards. When that happened, there was a clicking sound. If I use the emergency brake, it won't roll, but I have heard that it could be a linkage adjustment. Any ideas on how to fix this? It only does this in park. It doesn't slip out of any other gear or anything like that.

The next thing is that there is a leak at the gasket in the front of the transmission, near the modulator. At first, it was a tiny leak, just a drip from the gasket. So, I tightened all the bolts around the pan, but that just made it worse. So much worse, that most of the fluid leaked out. So, I decided to drop the pan yesterday and replace the cork gasket with a composite gasket. I did everything I should. Cleaned the rim of the pan, installed the gasket dry (as the fel-pro instructions indicated) and torqued the pan evenly to 12 ft lbs.

And still... a tiny leak right in the front of the pan, AT the gasket, near the modulator. It's not the modulator leaking out. It's in there good and tight. Any ideas on that?

Thanks, in advance.

Buz
Old July 28th, 2014 | 06:57 AM
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From: Mo-Ray-Al, K-Bec.
Try disconnecting the linkage and put the trans in park manually. It may be a linkage issue. Leakage from the pan is either a cork gasket that hasn't absorbed enough oil to swell up yet, or incorrect torquing of the pan bolts. Or the lip of the pan is dented.
Old July 28th, 2014 | 06:59 AM
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I'd go back and readjust the linkage, sounds like its not quite locking into park. On the leak, could it be leaking from the dip stick gasket?
Old July 28th, 2014 | 07:00 AM
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You didn't mention that you adjusted the
column rod with the trans fully in park
before tightening the small clamp bolt on the rod.
Also, did you change the O-ring on the modulator?

You could have a bad parking pawl or weak spring.
A trans guy may be more adept then myself, IDKSAT.
Hopefully, you just need an adjustment to get it to park.
Wipe the oil dry, and watch in a while for leaks. Good luck.
Forgot to mention the O-rings for the kick-down and fill tube.
Good catch Eric. There will be no kickdown cable on a 400.
Just caught that one, oops.

Last edited by tru-blue 442; July 28th, 2014 at 09:24 AM.
Old July 28th, 2014 | 07:06 AM
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Exactly how would I adjust the linkage?

Modulator was brand new before I got the transmission rebuilt. With the cork gasket, I could tell it's actually leaking from the gasket. I might drop it again and see if the lip is bent or something. All bolts were torqued correctly and evenly. Lol. I do at least know how to do that.
Old July 28th, 2014 | 07:52 AM
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From: Mo-Ray-Al, K-Bec.
Originally Posted by Arrowstorm
Exactly how would I adjust the linkage?
If you just disconnect it and manually put it into park and it works, exactly what adjustment is required will be evident. Sometimes it's simply a rod got bent removing it.


All bolts were torqued correctly and evenly. Lol. I do at least know how to do that.
But have you recently checked your torque wrench for accuracy? I know a guy that 'got a great deal' on a click type wrench, only to discover (too late) that it was 'horshshoe' brand .... as in 'close is good enough'. Turned out close wasn't good enough and his great deal cost him a great deal.
Old July 28th, 2014 | 08:15 AM
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Originally Posted by Professur
But have you recently checked your torque wrench for accuracy?
Didn't think about that since it is brand new and I've only used it twice. Lol. I guess I'll check into that.
Old July 28th, 2014 | 08:24 AM
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A quick and dirty how to verify your torque wrench.
http://gl1800riders.com/forums/showt...ration-testing
Old July 28th, 2014 | 04:20 PM
  #9  
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A little test showed me that it will only roll out of park backwards. NOT forward. Pushing forward, Park is quite solid. I will disconnect and inspect the linkage when I have a little time to get under there.

Also torqued the pan bolts to 15ftlb along with the modulator retainer. Will see if that helps.

Thanks for replies and any more insight into the matter! ={D>
Old July 31st, 2014 | 02:15 PM
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I haven't gotten to the parking situation yet, but I DID tighten up the emergency brake and that will do for now. I now have a miss in the engine to find and fix... =/ always something!

Yesterday, I dropped the pan and with a straight edge and a hammer, tried to straighten the edge out as much as I could. No dice.

Bought a stock pan (with drainplug!) and gasket on Summit for $30 shipped today and we'll see if that does the trick and stops the leaking.

Last edited by Arrowstorm; July 31st, 2014 at 02:19 PM.
Old July 31st, 2014 | 02:48 PM
  #11  
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Originally Posted by Arrowstorm
A little test showed me that it will only roll out of park backwards. NOT forward. Pushing forward, Park is quite solid.

Then your problem isn't likely linkage outside. When you've got the pan off, you should be able to see the internal linkage and the pawl engaging. I suspect the spring has sprung.
Old July 31st, 2014 | 06:08 PM
  #12  
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I will look at that when I install the new pan. What spring will I be looking for and can you possibly explain by what you mean is sprung?

Is something like this common with a fresh rebuild?
Old August 14th, 2014 | 05:07 PM
  #13  
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I got a new pan from Summit and installed it today. We'll see if that did the trick.

As far as the park thing...

With the pan off, I inspected and familiarized myself with the way the prawl engages the teeth inside the transmission to move it fully into park. The prawl is not full pressed against the teeth. The rod which presses against the prawl to move it up goes back and forth and all that, but it seems to be just resting in there when in neutral, able to sway freely, but when engaged in park, the whole rod pushes the prawl up into the teeth, but not as far as a little push of my finger against the prawl would.

I don't see any spring that could have sprung. Is there some illustration that I could refer to? There is a spring on the tip of this rod that is supposed to engage the prawl, but it doesn't seem to have any function. The bracket that holds the rod in place seems to just be a shelf so that the rod doesn't fall down into the pan.

Any ideas would be greatly appreciated. I tightened the parking brake pretty good and that will work for now. Also, I will wait until any responses give me ideas about the prawl before I fill **** baby up with fluid to see if the new pan fixed my leak.

Thanks in advance!

Buz
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