It's probably past time for me to service the diffs on my truck at 38k. Last time was 16k. I put Royal Purple 75w90 in the front and 75w140 in the rear.

1) Can I use 75w140 in both?

2) What is the service interval supposed to be?

Thanks!

 

I think the service interval is 30,000 miles.

 

if your talking about the 06 it's 15k silly i know but thats what dodge calls for.

 

I run it front and back in my 02. 30k sounds about right.

 

Dana corp axles were 30k, changed to 15k when AAM came on board.

 

According to book for the 03 it's 75w90 in both even if yo have limited slip. Take a good look in the manual.

 

I use 90/140 and change at 50k, but tow 90% of the time. If you are looking to stick with one weight, go 90/90.

 

The 15,000 mile drain interval for the AAM 11.5" Axle that Dodge recommends is absolutely retarded. GM trucks with the Duraturd have the same 11.5" AAM axle that Dodge has. Its fluid change interval is 50K.

Use a real synthetic and you can can go to 100,000 miles easily.

 

I believe his question was whether he can use 75W140 in front and rear diffs. If it were mine, I'd go with the heavier weight synthetic. If it was dino oil, I'd go the other way especially for the cold weather.

 

I'm using synthetic 75W-140 and a 50k mile service interval.

MikeyB

 

That is the question. I dug around and found that I had three bottles of Royal Purple 75w-140 left over from the first change at 16K. I also found that I have quite a few bottles of Redline 75w-90 that never made it into the 2002 before I sold it. After checking the prices on synthetic gear oil (and exclaiming "Holy #$@&!"), it looks like I'm going with what I have on hand. I'll get one more RP 75w-140 to make sure I've got enough for the rear and I'll put the Redline in the front.

Tad

 

On my last truck (03 3500) I ran Redline 75W140 in both front and rear with no problems.

I generally try to keep 75W90 on hand, though.

15K changes with synthetic is the spec for warranty for heavy service (who doesn't do short trips and towing?). After warranty I tend to go longer.

 

I do mine every 30K. Book stats 15K for sever duty and 30k for normal duty. I use Amsoil Sever Gear 75w90. You can use the higher weight and I wouldn't worry to much about the cold in Texas....LOL

 

This is an interesting post:

http://www.bobistheoilguy.com/forums...42#Post2045142

 

They're both GL5 and therefore you can mix both brands and viscosities without issue. If I were in your shoes, I'd put the 3 bottles of 75W140 in the rear, then top it off with a bottle of the 75W90. You'll end up with about a 75W127 in the rear. Then of course use the 75W90 in the front.

I change the rear diff every 30K and front diff every 60K, both with Mobil 1 75W90. Oil always drains out looking like new. I'm about 7500 lbs unloaded, and usually 17K-18K lbs GCW when towing, I tow about 20% of the time, and live in a warm climate. Currently at 160K miles on the truck. Personally, I think 75W140 is overkill in the 11.5 AAM if you're not hauling over the truck's GCWR and it is absolutely overkill in the front 9.25 AAM. Of course it doesn't hurt to run it, but it will drag down your fuel mileage a bit.