[oldroadiedog]

Rear end slipping?

I'll confirm these symtoms tomorrow but this morning when I went a few miles to get fuel in my '72 GT it felt like the rear axel was slipping only when I turned left. There is also a faint metallic rattling noise from the rear of the car I can hear while driving. Any suggestions as to the possible cause? I've just had the motor rebuilt, transmission sealed, body work/paint and will have a custom exhaust put on tomorrow. If the rear end is going out that would be a real drag. BTW...its a 3 speed stock automatic transmission. Thanks.

 

[jlthunder]

I'd check the rubber torque tube mounts. They may look good, but if you lower the front of the torque tube by removing the two bolts, it will then fall free and you can inspect the mounts. There will be 2 large mounts and one small one(on top). Caution, the tube is spring loaded. Place a jack under the mount as you remove the two bolts and then slowly lower the tube or it will come flying at you and knock you out. Inspect the large rubber dount which supports the center bearing. These also tend to rot out.

Just my 0.02

 

[oldroadiedog]

Yea, I got confirmation alright. I drove the GT into town to get a custom exhaust installed and while it's up on the rack the mechanic says "looks like your main seal is leaking". Great! So that's why I had to add 3 pints of ATF this morning. I just had the block completely over-hauled and the transmission supposedly sealed. I'm somewhat disappointed. What's involved in replacing the main seal? Dropping the transmission I would imagine. Does the block have to come off the motor mounts. Everything is looking and running so well otherwise.

 

[kwilford]

...the mechanic says "looks like your main seal is leaking". So that's why I had to add 3 pints of ATF this morning. I just had the block completely over-hauled and the transmission supposedly sealed. What's involved in replacing the main seal? Dropping the transmission I would imagine. Does the block have to come off the motor mounts?

So, was the tranny down the three pints, which would certainly cause slipping? Which means it's NOT the differential? But which "main seal" is he referring to? The engine rear main seal has nothing to do with the tranny leaking. Are the tranny seals leaking? Sorry, but I am a bit confused.

If the rear engine seal is leaking, you have to drop the tranny, remove the flex plate (the auto tranny version of a flywheel) and replace the seal. Tranny seal advice should come from someone who has actually worked on an auto tranny

 

[oldroadiedog]

It is definitly leaking ATF. The leak is showing up at the bottom of the bell housing which from what little I've read in the service manual could be the converter housing oil seal. This is probably going to be repair that exceeds my mechanic skill level. At this point I'm going to continue restoring the interior and get some bids to seal the transmission. Sorry about the confusion. Thanks for your interest though.

 

[GTJIM (R.I.P.)]

Th180

The only good thing is that the Opel auto trans is a standard GM Turbo Hydro 180 model that was used in many other GM small cars. It is often called the "Trimatic" or "Strassborg" transmission and rebuild kits are available for it from domestic auto trans rebuild kit suppliers. It was also extensively used in the Australian Holdens and some Suzukis too - I think.

 

[jerseyopel]

leaking seal

The seal itself is not hard to change at all, but it does require removing the transmission.When installing mine I used indian head gasket goo.Worked for years.

 

[oldroadiedog]

Another interesting thing I was told during that little adventure is that the small ATF cooling chamber at the bottom of the GT radiator doesn't work very well. Apparently the operating temperature of the ATF is much higher than the engine coolant. The mechanic said that the ATF causes the coolant to boil. I'm seriously considering adding a automatic transmission cooling coil in front of the radiator. This would involve lenghtning the transmission hoses - which need to be replaced anyway. Has anyone done this to their GT and what effect (if any) did it have on engine coolant temperature?

 

[GTJIM (R.I.P.)]

My thoughts on Trans Fluid cooling

I have a Trans cooler to fit into the line but am carefully considering where to put it as the Trans fluid does need to be kept up to temperature to work correctly - without over heating.

So I am thinking put an oil to air cooler in the line before routing the fluid through the original fittings in the bottom of the radiator. This would serve three purposes:

Vis: 1) removing heat from the trans fluid. 2)bringing the Trans fluid back to lower radiator temperature which will be cooler than the heated fluid but warm enough not to over cool the fluid 3)Remove heat from the radiator in another way to help with coolant temperature control.

Maybe a Thermo by-pass will be needed for extreme conditions when lots of heat needs to be removed from the Trans fluid ..... ??

 

[bear]

GT Jim and Old Roadie Dog, On both my motorhomes there is an air to oil tranny cooler in front of the radiators. The major piece of knowldege needed to install this type of cooler, or any cooler for that matter, is to know which line is pressure and which is the return line. For a single air to oil cooler the pressure line goes into the top of the cooler and the bottom would of course be the return, same as in the coolant radiator. So to route the tranny lines to a cooler in front of the radiator, it is imperative to know which line is which. Also, be sure to check the fluid level with the engine running, the cooler can take as much as a quart of ATF, depending on size, and when the engine is shut down the tranny fluid will drain back into the tranny sump pan. HTH.

Ron

 

[oldroadiedog]

Ron said,

"Also, be sure to check the fluid level with the engine running, the cooler can take as much as a quart of ATF, depending on size, and when the engine is shut down the tranny fluid will drain back into the tranny sump pan."

That's an interesting note because over-filling the automatic transmission will cause seals to fail. I'm not sure if that applies to when the car is parked or not. To be on the safe side...I think mounting the trnamission cooling coil at the lowest possible elevation in front of the radiator would help prevent back-flow. As to routing the ATF though the tansmission coil and then into the radiator cooling cell...I'm inclided to think that will be un-necesscary in my climate (mid-south). Although it can get pretty cold in the winter months; I generally don't drive my GT much during the winter. My main focus is to make the transmission leak-free and reduce engine coolant temperature.

 

[bear]

Actually the tranny coolers and engine oil coolers are located at the bottom of the radiators, I would presume for that reason. On my 71 Dodge van with a 426 727 hemi tranny, the pressures in the tranny get up to the 800 psi range, so with no where for the fluids to go, if over filled, I can see where the seals would leak. But with the engine running the fluid would be circulating and at a normal operating level. By having the pressure line enter the lowest part of the cooler and the return at the top, you would have to fill the cooler before the pressure from the pump got back to the tranny and could have an impact on the operation until the cooler was filled. Not too sure how the flow is inside the tranny, just a possible conjecture of what could happen. JMTCW.

Ron