Dodge 8.25" rear lube

[Hokiefyd]

I've got a '97 Dakota, with the 8.25" rear. It makes a small amount of whine, but only at certain speeds (40-45 mph). I hear it's very normal for those units. Plus, mine has 175,000 miles on it, so who knows what it looks like inside.

The previous owner put Mobil 1 in the rear. Don't know the weight. I understand the recommended weight is either 80W-90, or 85W-90 (I've seen both specs). Anyone on here with a Dodge 8.25" rear, what are you running? Here's what I'm thinking:

1) I want to change the rear fluid out, just so I know what's in there, and the level. I'd like to use Redline, just because of how much I like it in the MT in my Corolla. But open to any brand, of a reasonable price.

2) Does anyone with a Dodge 8.25" rear run something like a 75W-140 or an 85W-140? Did you notice any quieter running with the thicker oil?

3) Will I lose any measurable fuel economy by using a -140 oil vs. the -90 oil?

4) On the "thinner" side of the scale, Redline (and others I'm sure) sell a 75W-90. Should I have as good of a result with that as anything?

Temperatures here are in the 90s in the summer and 40s in the winter. Super cold never happens here. Plus, I only drive the truck about 5,000 miles per year, so fuel economy actually isn't the #1 concern here.

Any thoughts or recommendations would be appreciated! Thanks.

 

[Johnny]

According to Amsoil's site, you can use either 80W-90, 75W-90, or 75W-110. I really like their SVG 75W-110.

 

[Jim Allen]

If you use a 75W110 or 75W140 synthetic, you'd lose a bit less than if you went with an equivalent mineral oil, but I don't think either of those are necessary nor would they be particularly beneficial. I'd stick with a good 75W90 syn or 85W90 mineral. With the miles on that truck and the low use, I'd look for a mineral gear oil. Chevron makes a really top notch mineral product at a good price. Shell's mineral gear oil is good too.

 

[Huie83]

I have the crysler 8.25 in my Jeep Cherokee, 159K miles and wines a bit like yours but is fine overall.

I use Mobil 1 LS 75W-90 @ $9 a bottle, it's hard to beat. This is specked in the manual and is a full synthetic fluid. 80w90 would be fine too.

I like the Mobil because it is synthetic and flows better in the harsh winters here in MN.

I guess you could go with a 75W-140 if you tow or something, it also may quiet the rear a bit.

I was thinking about going with the 140 to quiet the rear a bit but was nervous about the winter, something you don't have to worry about.

 

[Greaser]

Same here have a 99 Cherokee with the 8.25 Chryco rear.Have around 278,000km. on this truck.It has always had 75W-140 syn. in the rear due to towing with this rig.I bought it with the tow package new and most of the lube has been Pennzoil gear lube with regular changes all it's life.No problems.

 

[Hokiefyd]

Thanks guys. I happened across this statement on Redline's website, about its 80W-140:

"Generally used in commercial trucks which will climb long, steep grades and some racing applications where power is not critical. Generally 0.5% less efficient than 75W90. Can also be used in differentials and transmissions where excessive noise is a problem and limited-slip differentials which vibrate excessively when turning a corner. Exceeds API GL-5."

It claims a loss of 0.5% with this heavy oil compared with the 75W-90. To me, that's really a non-issue, that apparent small change. I think the original owner towed something with this Dakota, because you can see the outline of a platform hitch's mount on the rear frame rails, under the truck. That hitch is gone now, and the 2nd owner, from whom I bought the truck, did not tow or have a hitch. I'll eventually likely be towing a boat with this truck, but currently, just a small utility trailer on a bumper ball.

I think I may look into the heavier fluid, in a synthetic. It's HOT here more than anything else, and with the slight bit of gear whine, I'm interested to see if the 75W-140 will quiet that down. I put an AEM Brute Force intake on it and the previous owner has a Flowmaster system on it (which sounds better than I figured it would). Even if I lost 0.5 MPG (which would represent a ~3% loss in fuel economy, I wouldn't really notice or care. It doesn't appear that a -140 grade oil will hurt me even that much, so I may just try it.

Any further thoughts are always appreciated. Thanks again.

Edit: oh, also, my parents had an '89 Cherokee Laredo, with the 4.0L. I assume also an 8.25" rear? I dunno, maybe it was a Dana. Anyway, we moved across the country, from CA to VA, in the summer of '91 after he retired from the Navy, and I was just a young'un. We pulled a 20' travel trailer across, and did a 2 week vacation, seeing the sights. How is this related? The rear end burned up about 2/3s of the way through. Convenient, as my grandparents are in MI, and we planned to stop there anyway for a while. A Jeep dealer there replaced the rear axle. Who knows what the problem was, or if it was lubricant-related, but I have seen a rear end burn up when towing, so I guess I'd rather err on the side of safety.

 

[Jim Allen]

That '89 XJ would have had a Dana 35, the fairly notorious American Motors car axle formerly known as the AMC-15 (little brother to the AMC-20). The Chrysler 8.25 is a much better piece.

 

[UNC017]

I've owned a lot of Chrysler 8.25s over the years, and I've found them to be extremely forgiving of what you do to them (one of the ones I still own has over 435,000 miles on it, and it didn't get its first oil change until well over 150,000 miles). I've also got one in a '99 Cherokee, and my father has one in a high-mileage '92 Dakota.

Interestingly, I've never had an 8.25 that made *any* audible noise. The old Chrysler 8.75 (third-member style axle similar to the Ford 9") has certain gear ratios that are consistently noisier than others, but I personally haven't experienced that with the 8.25. The 8.75s I've owned that had a hum did respond favorably (quieter) with synthetic lube- that seemed to make more difference than the particular viscosity grade. I tend to use 75w90 most of the time, but I've also run 75w140 with little noticeable difference.

 

[UNC017]

Originally Posted By: Jim Allen
That '89 XJ would have had a Dana 35, the fairly notorious American Motors car axle formerly known as the AMC-15 (little brother to the AMC-20). The Chrysler 8.25 is a much better piece.



And oddly enough, the Dana 35 hung around in some versions of the XJ until the end of production and it was, IIRC, the axle you automatically got (stuck with) when you optioned the truck with ABS. Non-ABS Cherokees got the better 8.25, which itself got upgraded somewhere around 96 or 97.

 

[Hokiefyd]

Interestingly enough, I saw some Castrol Hypoy C in Pep Boys today, in two viscosity grades (75W-90 and 85W-140). From the PDS on Castrol's website, it looks like the 75W-90 actually has a higher viscosity than the 80W-90 does (which I didn't see in stock).

The Mobil 1 GL-5 they had there (don't remember the grade) was prohibitively expensive ($17.99/quart). Even the Royal Purple was just over half that, at $9.99. I may check again to see if the Mobil 1 was just in the wrong slot on the shelf. Will also surf other retailers to see what they have. It looks like, in general, sticking with a 75W-90 is you all's recommendation, so I may just go with that. That 75W-90 Castrol Hypoy at $6/quart looks pretty good.