Just got my first Cummins (see signature) after reading on the forum for a while. (Have a 7.3 Powerstroke and got tired of getting beat by all my buddies with there Cummins) Anyways, the dealer I got the truck from replaced the front differential pinion seal. After a decent drive, the front diff cover gets pretty hot (need to get out the temp gun when I get home). I am wondering if the screwed up the pinion bearing preload when the put it back together. It is defenately hotter than the rear diff. Any thoughts on this?

Thanks,
Tobin

 

Correct - front diff should not be hotter.

Did they re-use the crush sleeve?
If so, particular care must be taken to attain proper preload (obviously important when new sleeve is used as well).

Actual temp readings from both diffs will dictate your next move.

Also, consider changing gear oil in both diffs with known quality & quantity.

 

I have no idea what they did besides change the oil seal. Honestly I have a hard time trusting them to put wiper blades on correctly. I will take a look at the fluid, mabey just take it apart and re-do it so I know it is done correctly. Last thing I want is that thing to bind up, throw the driveshaft off into the oil pan and rip the bottom end out of the motor! (my luck)

Is it just standard gear lube in these diffs? New Dodge guy here, used to all the Ford stuff.

Thanks,
Tobin

 

Rear diff - if posi - is gear type, so no friction modifier needed for clutch packs... of course the front diff is open.

Obviously, synthetic is better, and 75W-140W is better than 75W-90W.

200*F rear diff gear oil is common.

Synergen is the best in my experience.

 

I'm assuming you are seeing a hot diff, after going downt he road.
I don't have 4x4, but I'm wondering if the front hubs are locked? Shouldn't the front diff NOT be turning while on pavement?

Tony

 

Front diff always turns on these trucks.Book calls for 75w90.full synthetic gear oil.That is what comes in them.Only notes showing the 140wt is on the axels used in the 1500s.

 

TonyB-
I wish the front end was unlocked, but the whole front end turns even when it is not in 4x4.

200*F temps are normal in these diffs? I don't think it is getting that hot, but it is a little hotter than the rear. I will break out the temp gun when I get home from my 15 mile drive home from work.

Thanks,
Tobin

 

the front axles are turning, so is the front drive shaft. they just are not turning under power from the t-case untill you engage it.

 

so much for that theory!

 

My front diff runs around 140° F under normal driving. I've seen it as high as 200 when pulling around 10k for extended time on the interstate.

--Eric

 

120*F for the front diff and 105*F for the rear diff with a infared temp gun on the differential covers on a 15 mile drive home. I guess I might just let it be untill something falls apart.

Thanks,
Tobin

 

What could cause a higher temp on the front differential when towing? The front end has no load on it power wise. Is it just from the added weight on the bearings?

 

I've actually wondered that myself. I'm sure if I would have weighed the axles front and rear that the front would've been carrying more weight than empty...but I don't know how much that would effect the front diff temp.

One of these days, I'll hopefully install a dynatrack manual hub conversion kit and see if that eliminates the heavy towing/high front diff temp connection.

--Eric

 

Also, measuring temp by infra-red in this application is very susceptible to inaccurate readings due to the instrument's sensitivity combined with a large potential for aiming inconsistencies.

 

Aiming inconsisencies? Hold the thing up to the diff and pull the trigger, its not like a sniper shot. I know the thing isn't too accurate, but what can it be +/- 10 degrees?

Tobin