Trans Leak

[Bulten Rauder]

I have fluid leaking from the transmission seal. I've replaced the seal with OEM and it still leaks just days later:mad2:. What is the likely cause? Local tranny shop suggested the shaft can have flat spots? How would this just happen at 140Kmiles? Should I replace the bushing inside or just try the driveshaft yoke?

Thanks,

Dave

[Darrin]

Often times what happens is that you are having driveline vibration enough to do damage but not enough to maybe feel. The bushing gets hammered and you will have a leak no matter how many times you replace the seal. You need to replace the bushing to fix it.

Darrin

[FordNut]

And the driveshaft. 4.10's have been known to cause the rear seal to not last if the original driveshaft is retained.

[Bulten Rauder]

Thanks guys.:burnout:

I'm at a complete loss as to how 4.10's at the back could possibly affect the tranny tailstock. They have nothing to do with each other :confused: . Besides, this tranny is in my CV with stock old man gears.

There are vibrations and always were...perhaps wheels/tires, driveshaft, motor balance etc.

I've heard the bushing inside has two shims? The bushing could be toast. This would mean removing the tailstock...and then what?

Dave

[FordNut]

4.10 gears affect the rotational speed of the driveshaft, so it is going faster at a given road speed. That changes the "critical speed" of the driveshaft. Both ends of the driveshaft are affected, but usually it is only the transmission end that leaks. In severe cases it will actually push the seal totally out of the tailhousing and spray fluid all over the place. There have actually been some cases of the tailhousing breaking.

[lincolnpimp]

Yup.... I just pushed the tail seal out of mine. and am waiting on the dr shaft now!!!

[FordNut]

There are a few options to fix it. Find a CVPI MMX (metal matrix) driveshaft, get a Dynotech MMX driveshaft (gotta find an old one, they're no longer made nor are the CVPI ones), get a carbon fiber shaft, get an aftermarket shaft with high speed balance (some limited success with this method), get the factory shaft rebalanced at high speed (not much luck with this one either). There is one source for MMX driveshafts that I've found, it's Mark Williams Enterprises. But it's not a direct bolt-in swap.

[Bulten Rauder]

As I stated, there are no 4.10's in this Crown Vic as it's stock. Original everything. Nothing has changed. Last Summer, we noticed the leak and had the seal replaced (not OEM!). Just noticed it leaking again a month ago so we replaced it with the OEM seal. It pretty well didn't stop the leak at all.

Do you think I should still replace the driveshaft first? What about getting a driveshaft from the wrecker?

What is this bushing all about? I didn't think there should be trans fluid in the tailstock at the seal?

Thanks,

Dave

[FordNut]

As I stated, there are no 4.10's in this Crown Vic as it's stock. Original everything. Nothing has changed. Last Summer, we noticed the leak and had the seal replaced (not OEM!). Just noticed it leaking again a month ago so we replaced it with the OEM seal. It pretty well didn't stop the leak at all.

Do you think I should still replace the driveshaft first? What about getting a driveshaft from the wrecker?

What is this bushing all about? I didn't think there should be trans fluid in the tailstock at the seal?

Thanks,

Dave

Sorry, I was looking at your signature and assumed it was the Marauder and 4.10's that was causing problems.

You will certainly have to replace the seal, and the bushing is also a good idea. The standard CV driveshaft is steel and is longer than the Marauder or CVPI driveshaft, which makes it even more prone to balance issues. It is possible that re-indexing the driveshaft could reduce the vibrations. I don't think you can switch to a CVPI or Marauder shaft unless you swap the tailshaft housing (and probably output shaft, too). Might be a good idea to go to a drivetrain shop and have the shaft balanced while it is out for the seal and bushing replacement.

The bushing is lubricated and ATF does go all the way back to the rear seal.

[lincolnpimp]

Replace the tail shaft bushing is a MUST! Only replacing the seal, will definately lead to instant leak again. I would say that unless u are running consistant sustained speeds over 105mph, then your drive shaft would most likely be fine with a simple balance.

Jeff

[Bulten Rauder]

Many thanks guys.:beer:

I'll track down a DS and get that bushing replaced. Should be easier than finding the MM DS.

Wife is whining about the fumes from the exhaust burning off the ATF:shake:...at least the floor will never rust!:P

[lincolnpimp]

Ya, a tail shaft leak smokes like a b****

[juno]

Ya, a tail shaft leak smokes like a b****

Try blowing a Torque Converter on the back side of Sebring!!! That is some smoke. :)

[Bulten Rauder]

Maybe I'll put some good 'ol Canadian pork fat in the tranny...:cool4:

[Thunderace]

While your replacing the tailshaft bushing check for slop in your pinion bearing also,that caused some vibes for our GMarq.

[Bulten Rauder]

Popped the new bushing and seal in today. No slop in the pinion:). There was quite abit of play at the yoke though...:shake:

Will keep an eye on the leak but should be OK now.

[FordNut]

Good luck.

[Bulten Rauder]

Good luck.

I meant there was play initially, now there is none.:beatnik:

Yoke looked perfect.

[FordNut]

I meant good luck with the driveshaft not wrecking it again. Honestly, good luck, I'm not being sarcastic...

[Bulten Rauder]

10-4. :burnout:

I noiced a drip again today:mad2:. :bigcry: :banghead:

I can't believe it. Maybe it's just some left over fluid making its way down. With a new bushing and seal, it should be impossible to leak for at least a few days minimum?! It drives smooth as silk. Everything seems tight.:confused:

I'll clean it off and keep an eye on it.

Otherwise, time to upgrade the wife into something newer...:eek:

[Bulten Rauder]

Last week I cleaned under the tailstock, driveshaft and underbody. It seems the leak is fixed! :banana2:

I scrubbed the exhaust so it should smell a little better soon...:sweat:

Dave

[jdenning002]

I am having the same issue, I repalced the seal and it is leaking again...

I called the parts dept at my local dealer, they say that the bushing is not sold seperatly... Where can I get one??

Thanks!

[FordNut]

Any trans shop should be able to get one.

[ctrlraven]

How much would the tail shalf bushing cost to replace, rough guess? I think it would be wise for me to replace mine with 130k + miles on it and plan on having 4.10s installed soon.

[jdenning002]

I picked up another seal, under $8.00 I will look for a bushing at a trans shop tomorrow...

[Krytin]

How much would the tail shalf bushing cost to replace, rough guess? I think it would be wise for me to replace mine with 130k + miles on it and plan on having 4.10s installed soon.
Check into the tailshaft bushing lube mod.
I think DR was offering a tailshaft all done up on an exchange program and the Jerry W. write up on the transmission that includes instructions for improving shifts (the infamous "J-Mod") also out lines how to modify the tailshaft bushing.

[Stranger in the Black Sedan]

I have replaced rear bushings in autos but not specifically the 4R70/75s. On any other transmissions you just took the tail housing off, 4 bolts, and drove the bushing out with an appropriately sized socket or other home made driver tool (or autozone or the like rent bushing driver sets w/ aluminum drivers) and then drive the new bushing in with a block of wood. Is there anything different about the 4R70/75 or is it the same idea?