Question.
I've got a leak with my new factory 4R70W transmission (Yes, it's been replaced once already). I've put about 3500 easy miles (no towing) on the unit. It's leaking from the seal around the driveshaft. Not much, but it drips on the exhaust and is starting to spot my garage. Any thoughts as to what's causing it/what I need to be aware of when I talk to the dealer. Plan to take it in soon - this holiday in the middle of the week screws things up...
Thx.

 

StrongWind,
I have A 2000 HD with 11,000 miles and the rear seal totally walked out of the housing and caused a major mess. Towed it to the dealer, but the dealer would not put the seal back in because they said the computer had been messed with. Over-revved the engine they said. No factory warranty work could be performed because of this mod. What crap! I towed it home and put the seal back in (w/sealant this time) added two quarts of ATF and all is well. In short, replace the seal and put some Ultra-blue sealant around the metal contact area at the rear housing. Dealers suck!

 

Obviously it needs a seal, but they should examine the driveshafte yoke and tailhousing bearing condition for wear. Since the driveshaft was previously removed during your transmission replacement, I would crawl under and check if the driveshaft was installed in the position it was removed. There should be yellow marks that line up on the rear end and the driveshaft. Do you have any driveline vibration?

 

Max,
Thx for the help.
When the trans was replaced 3500 miles ago, the service ticket indicated I also got my driveshaft blanced. Here's what it says on the ticket

"42 Rear bushing spun BPN -7000...4602
Road test to verify concern. Perform NHV diag drive shaft runout R-0.035 C-0.013 FNT -0.011. Remove drive shaft retest vibration present. Tail shaft bushing spun. SOP trans throught hotline. R&R automatic transmission, R&R drive shaft, Road test. Operates as normal. Check balance Off 2-1.0..1-.75. 1-.75 rebalance."

As for driveline vibration, I seem to have some vibration at low end (ie accelerating from a slow roll) once up to speed, I don't really notice anything. It's not like it was before they replaced the transmission.

What should I "suggest" the service department do? Less than 6000 miles to date. I believe I will have their UNDIVIDED attention on this one.

 

You're Welcome. When the driveshaft is out of balance it is hard on other parts. The tailshaft has a bearing that the yoke rides in. When the vibration persists, both of these areas have added wear from the additional loads. Once slack is there from either/both parts, the additional play ruins the rear seal. They must evaluate/correct this situation and correct the vibration or it will return. As for getting this accomplished, they should do/know all of this. You should simply have to keep on them. I would suggest only dealing with the service manager, and if no satisfaction there, ask for the zone rep. You can monitor vibration, leakage, and keep thorough records documenting the issue for future troubles. If the problem takes several repairs, I would ask for an extended warranty.

 

Thx again Max. I'll keep everyone posted on my progress.

 

max:
I recently had the rear pinion seal replaced on my truck. It had developed a small leak. Could this be due to an out-of-balance driveshaft or just "one of those things"? I was surprised to discover that the service dept had "smothered" my rear differential housing with that black "self-healing" stuff that they put on the frame. It made me wonder if they did that to make it more difficult to spot any future leaks. They didn't cover the differential cover, only the front side of the pumpkin. Originally it had the Ford black/rust color scheme.

 

Do you seem to be having driveline vibrations? The pinion gear is supported very well by 2 spaced out pinion bearings. Generally, it would take alot of vibration damage (or general wear) to wear enough play into this area to cause secondary damage to the seal. There are other things that may have caused the seal to leak, like: poor initial rearend assembly, improper pinion bearing preload, or metal shavings getting in it from break in or wear/damage.

 

max:
I haven't noticed any driveline problems with the exception of a very slight seat-of-the-pants vibration at 70mph. I put it down to wheel balancing but could be wrong. I haven't had the wheels balanced or the alignment checked since I bought my truck in April of '00 because the tires are wearing very evenly and the truck drives straight as an arrow. I guess I'm due for a check though.

I figure that my seal was either installed incorrectly or was defective from the start. Now if it happens again then I'll be more concerned.