Front 30a and rear Corp 8.25 Slippery Stuff?

WoodysKJ · **Posted:** Mon May 19, 2008 12:41 pm

Hey,

I just read in the Wiki link that was posted in here that the Dana 30a and the Corp. 8.25 can BOTH use the 75W-140 synthetic stuff and that it is recommended if towing any and/or offroading.

Is this good advice? My owners mannual says to (for Schedule B) use the 75W-140 synthetic in the rear and to use 80w-90 for the front.

Any input would be great. Gotta do this soon.

JJsTJ · **Posted:** Mon May 19, 2008 1:10 pm

Yes. Good advice.

You can use a 75w90 in the front and rear if not towing or 75w140 in rear if towing. Can also use w140 in front too if you like.

FWIW, I split the difference and use 75w110 in all diffs in all my Jeeps.

bugnout · **Posted:** Mon May 19, 2008 1:40 pm

I've been using 75W140 syn in both since the first fluid change. I think it makes it quieter and better fuel mileage. No imperical evidence though.

snowsport · **Joined:** Tue Oct 18, 2005 11:52 pm **Posts:** 1211

I've had 75W140 Amsoil front and back for quite a while now and no problems. Slow stuff to pump into the diff when you're changing. Kind of stiff at -40C also, but it warms up quick enough. :twisted:

tommudd · **Posted:** Mon May 19, 2008 8:09 pm

75W140 front and rear now for over 75000 or since I changed it the first time no problems

WoodysKJ · **Posted:** Tue May 20, 2008 9:43 am

I guess what I am asking is...

And i know this isn't a chrysler sponsored site or even a final authority on warantee issues, but....

I think I see conflicting info in the owner's mannual. Can I run the 75w140 in both with out any issues that MIGHT be a reason for the stealership to void my warantee. The way I read things is that the 75w140 is supposed to be used in the rear IF towing and/or offroading but says the 80w90 is for the front.

Does my climate make a difference? Tommudd, you are in roughly the same climate as I am.

tommudd · **Posted:** Tue May 20, 2008 10:46 am

To be quite honest here the first time I did the diff changes I grabbed the wrong bottles and filled the front. I always have at least double everything in my garage, so I grabbed the bottles I had sat out for the rear and put in the front , but after I did it I thought not wasting it and run it for a while BUT Since I do tow a lot and although do not off road as much as I would like the "hills" that I run around on in Southeastern Ohio put as much stress on everything as some do off roading esp. with a loaded trailer. So thats why I run it the way I do. As far as any warranty, they would have to prove that what you were running was a different weight and that the different weight is what caused the problem as to void the warranty. I know when I worked in a Ford Dealership we had regionals tell us to use a different heavier weight oil or diff fluid if a customer used his truck "like a real truck hauling things" due to the extra stress placed upon the gears etc.
I had my front diff cover off at 95000 miles and the gears etc looked brand new ( PITA to do but wanted to check them out) .
Not sure what everyone else says but for me its worked fine

spoonplugger1 · **Posted:** Tue May 20, 2008 11:13 am

No one at the dealership could tell the difference.

jeepkj02 · **Posted:** Tue May 20, 2008 11:21 am

spoonplugger1 wrote:

No one at the dealership could tell the difference.

I was at the dealership last week to get the oil changed on my parents GMC, the guy didn't know the difference between Dexron and Dex-cool. I highly doubt they can tell the difference between 75w90 and 75w140.

tommudd · **Posted:** Tue May 20, 2008 11:21 am

spoonplugger1 wrote:

No one at the dealership could tell the difference.

my point exactly unless they sent it away and they would not do that :wink:

WoodysKJ · **Posted:** Tue May 20, 2008 11:33 am

That is what i am thinking. I do plan to wheel it and I do pull a small trailer...

JJsTJ · **Posted:** Tue May 20, 2008 12:26 pm

Split the difference and go for the 75w110 in both. Dealer isn't going to analyze your gear oil for failure for warranty purposes and the most likely failure will be the case spiltting which dumps it all on the ground anyway. Since you probably don't tow in 4wd the 75w90 will be fine in the front but so would a heavier gear lube. Only downside to the heavy lube is the slight decrease in MPG's it might barely show.

tommudd · **Posted:** Tue May 20, 2008 12:34 pm

What do you mean you don't tow in 4 wheel drive

1/4 of my towing is in 4WD pulling logs / loads of firewood out of the woods, even moving my neice this weekend I had it in 4WD to get the final mile back to her new place :wink:

great place once you get there :lol:

But yes most people should go with JJsKJ and split the difference, because maybe you have a tractor to use instead of the KJ :lol:

Jeepjeepster · **Posted:** Tue May 20, 2008 1:01 pm

If its raining I always tow in 4wd.

Ive always used 75w-140 Castrol SYN in my diff's.

JJsTJ · **Posted:** Tue May 20, 2008 1:17 pm

I guess if you do tow in 4wd you know you should use the heavier lube. I have run all 3 weights at different times in the past and only switched to the 110 in all diffs because it was available and keeps me from having to keep different weights around.

Guest · **Posted:** Tue May 20, 2008 9:21 pm

I don't tow much...and when i DO, it's about 1,000 lb max (small utility trailer and a motorcycle), and sometimes a 2500-3500 lb vehicle on a tow dolly for a VERY short distance. I run 75/90 in both my diffs.

Front 30a and rear Corp 8.25 Slippery Stuff?

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