Front Diff Destruction

[Oldsmoke]

Seems like I must be loosing a bearing in the front diff! Smelled leaking oil so stopped to check and found oil pouring from pinion shaft seal and from left axle seal. The case was so hot I could hardly touch it. Limped home at low speed without hearing any clunking or grinding so hope to fix'er up.

Should I rebuild or just get an new one from a wrecker?

[grancito]

Were you driving a lot in 4wd? if not, the front diff is engaged when it shouldn't be. If it is not noisey, just replace the seals.

[Oldsmoke]

It all started when I put the truck in 4wd to climb uphill from gravel onto a paved road. I took it out of 4wd right away but have a feeling that for some reason the diff did not properly disengage. I was pulling the RV trailer at the time but would that make any difference? Anyway, I talked to a master mechanic at the local garage who said he had seen this before and just takes out the diff and sends it out for rebuilding.

[grancito]

If your tires are worn different, or different brand, the size will be different between the front and back and the transfer case will not release the front drive until you back up some distance. The heat was probably from drive train wind up from different tire size, which has damaged the seals. Just change the seals, cheap.

[Oldsmoke]

So the diff is heating up and blowing oil because the solenoid engagement device is not functioning properly. So maybe if I replace the solenoid and seals I will be OK? There is no growling or grinding noises coming from the diff as yet.

[Oldsmoke]

Tire sizes are the same although the back tires are from a different manufacturer than the front.

[Oldsmoke]

I think I'll go with the drive train wind up idea and try just changing the seals. Does this mean I will have to get a whole new set of 4 tires? :eek:

[grancito]

The different manufacture is the problem, they are not exactly the size they say. My suburban has very slightly different ware front to back, and the soleniod is OK but it does not unlock on hard ground. You can feel the 4wd engaged on a turn by the stearing putting intermitent resistance and a whine as the speed increases. Reversing a small distance unwinds the system and it releases.

[grancito]

I think I'll go with the drive train wind up idea and try just changing the seals. Does this mean I will have to get a whole new set of 4 tires? :eek:

No, just make sure it comes out of 4wd before driving too far on hard ground.

[Oldsmoke]

OK, thanks Grancito. Will give that a try.

[grancito]

OK, just try some more oil, perhaps now that it has cooled down, it won't leak.

[Oldsmoke]

On further investigation I found the left front axle shaft to be flopping around pretty severely. Obviously the bearing has failed where the shaft comes out of the diff. With 292,000Kms. on that front diff I may as well pull it and put in all new bearings and seals.

The guys at the transmission shop say I did exceptionally well to get that far on the original front diff.

[grancito]

Good idea to rebuild, one from a junk yard could be at the end of it´s life.

[JD_countryboy]

Friend of mine has seen this problem a few times. Time for a new diff for sure. Depends on if the pinion bearing siezed, and spun in the aluminum case. I havent seen them get rebuilt, just replaced with new from gm, expensive. While your droppin all that $ in your front diff, id suggest the 4x4 posilock system to be installed. Cheap and simple insurance to monitor that you don't have such a problem again.

[Oldsmoke]

Hauled the diff out yesterday. Wasn't too bad a job and only took an hour or so. My GM service manual does not go into repairing the diff but I will give it a try. I want to put new bearings and seals on the output shafts. Hopefully the case is not damaged from the bearing failure.

[Oldsmoke]

Pulled that diff apart and really can't see any damage other than a small piece of what I am assuming is the round wire type circlip that held the axle into the splines in the carrier. The inner bearing race for the tappered bearing seems a little loose as it just fell out of the case when I turned it over but doesn't look like it has spun. Seal was cooked but the bearings are actually in passable shape. Can't see any evidence of binding on the gears.
Didn't disassemble the pinion shaft but it turns nice and was not leaking oil.
Still debating whether or not to take it in to the transmission shop for inspection and repair.

[JD_countryboy]

I'm fairly sure the inner bearing race shouldnt have just fallen out. That is the only thing that makes me wonder.

[Oldsmoke]

Ya, I know. The diff needs a total rebearing and seals. Gears and axles all look OK tho. Hopefully I can loctite in the new races. How do transmission shops like basket cases?

[grancito]

Locktite works great for loose bearings, can't remember which one, but read the guide.

[JD_countryboy]

Its called Sleeve Retainer. I think its green As far as basket cases, i'm guessin it depends on where ya take it.

[Oldsmoke]

I have it in my toolbox. It is a great product. I have used it on lots of repairs to worn parts.

Actually the bearing races I talked about in my diff are a "floating" design. They tighten up when the case comes together and the preload comes on from the tapered bearings.

A local transmission shop quoted me a total rebearing and seals overhaul for $350. so I took I let them have the job. It will be good to know that it has been done right.

[Oldsmoke]

Picked up the diff from the shop today. The guy said the bearings were worn but that was not what caused the heating, seal failure, and oil leakage.

In the future I will be much more careful about matching tire sizes and not driving in 4x on dry pavement. He said that just a tiny difference in tire circumference can cause binding and problems with disengaging from 4x.

[Chevylover]

Picked up the diff from the shop today. The guy said the bearings were worn but that was not what caused the heating, seal failure, and oil leakage.

In the future I will be much more careful about matching tire sizes and not driving in 4x on dry pavement. He said that just a tiny difference in tire circumference can cause binding and problems with disengaging from 4x.


Or go with a Posi-Lock system, THAN you WILL know, when it is engaged or not ! And as a bonus you'll get 2L.


Cu,
Sven

[Oldsmoke]

Yah, I still have to check my transfer case to make sure it is disengaging properly.

Is this posi-loc some kind of modification to the GM transfer case, a bolt on, or a whole new transfer case?

[Chevylover]

Yah, I still have to check my transfer case to make sure it is disengaging properly.

Is this posi-loc some kind of modification to the GM transfer case, a bolt on, or a whole new transfer case?

Have a look here :

http://www.ssdieselsupply.com/product_200_PosiLock_4x4_Positive_Axle_Engagement_ System.html

Hope that will explain everthing you wanna know. If not, feel free to ask.

Cu,
Sven

[Oldsmoke]

Hey, thanks Sven, that looks like a real good idea. I often wondered how much of the heat build up in the front axle comes from the "thermo nuclear" engagement device. Man that thing is an accident waiting to happen.

I might get one of these.

[Chevylover]

I installed mine after the factory TLA failed. The costs (TLA vs. Posi-lock) were nearly the same for me here in germany, so I decided to go with the posi due to some facts : won't disangage when ignition is turned off, the 2low and you can leave the front diff engaged while gone back to 2 high, so you could engage 4wd at any speed you want (same as manual locked hubs).

I am really satisfied with it and it works when 4wd is needed.


Cu,
Sven

[JD_countryboy]

THe posi lock is the only way to go in my book. it is cheap insurance, and a good way to monitor if your front end is locked in or not. THe hardest part of the install is getting the front diff bolts loose to mount the posilock braket. You already have that done, so it will be simple for you to add now.

[Shawnethan]

This sounds like a problem I am having. I cannot engage my 4X4 high with the mechanical stick but it seems as if the front axle is engaging at times. I noticed my tires have different wear patterns and manufacturers could that be the cause? I have pulled both the electronic sensors (one on top X-fer case with 3 wires and the one in the rear with two wires) with the purpose of getting replacements. Does this posilock system seem like a better solution along with 4 new tires?

[JD_countryboy]

The posi lock is for positive mechanical engagement of the front axle only. you still have to shift your tcase seperatly. This eliminates the sensor on the tcase that tells the original TLA to engage front axle. If your having a tcase problem this will not fix the tcase. Must keep matched and evenly worn tires on a 4x4 if you want drivetrain to last.

[Shawnethan]

JD - thanks! Fixed the problem with a front differential actuator and a new set of tires. I can honestly say I have never heard of having to have same tires on a 4WD and I have had 4WD for 20 years - thanks for the head's up!

[JD_countryboy]

No problem. Missmatched tires on a 4x4 is always a bit of trouble. To keep the least stress on the the drivetrain the even tires are needed. otherwise the different circumfrence of the uneven tires causes components to spin at different speeds.

[Husker 6.5]

Definitely, even the same sized tires new from different manufacturers will have different circumfrences, as will different styles from the same manufacturer. This is why it is very important that you follow the manufaturer's rotation interval and also rotate the spare in the mix. This not only keeps the treadwear and tread depth even (critical for 4WD) but it evens the wear over all five tires and actually extends the life of your tires overall.

If you have to run different tires, at least run the same pairs on each axle, and the largest on the rear. Engage 4WD only when you are on a surface that will allow the front axle tires to slip so they can turn at a higher speed (ie: mud, snow/ice, sand) and do not use 4WD on dry pavement, and get four matched tires ASAP (spare if applicable, too).

Husker 6.5