Mopar rear diff pinion bearing woes-just FYI

joetheis

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I just got done rebuilding my '93 Dodge Dakota rear diff.
8 1/4" diff.
Seems that IF you tow or haul heavy with them the rear pinion bearing fries!
(I bought my truck cuz it HAD the towing package)!!!
I had replaced the oil last spring with Mobil 1 75-90 before the 250 mile haul, on the way home I started to hear the "growl" thought it was tires.
A few weeks ago it got too loud.
Had to do a total rear axle rebuild.
This time I switched to Amsoil 90-140 heavy duty oil.
Keep and eye on those rear diff. temps, swap your oil as oil break down may have been the cause of mine, (although the web is full of horror stories about Mopar pinion problems.
Would I buy another Mopar truck-in a heart beat!

Joe
 

alldodge

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How many miles are on the truck? If this was your first time changing the gear oil, then it could be it was more time then a 250 mile haul.
 

joetheis

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The truck had 130,000 ish miles, close to 132,000 when I did the diff.
I believe it was the first time it had ever pulled anything, (I had to install the class 3 hitch).
The oil that came out (petrolem bases gear oil) was clean, no metal flakes, so it wasn't THAT old either, the P.O. kept after this truck, (I wrestled with what kind to drop back in Dino or synth.)
The Mobil 1 had maybe 500 miles, (maybe 15 miles hauling boat to see how the truck and trailer road), prior to when I hauled my boat up.
It was mid April, was cool out. I took my time, 65 all the way up. Stopped at Preble rest area maybe 120 miles from my house.
No noise at that point.
Actual miles is 220 from my house to French Creek Marina, Clayton N.Y.
Truck was used very little all summer before I hauled the boat home, (ran @ to keep the seals happy, use up fuel).
Rear wheels were never in the water and IF they were not to the axles.
220 miles back home.
I actually started to hear the noise a few miles from Clayton, so the bearings started to peel then. never got any loud(er). Installed snow tires, so that masked the noise til it got bad.
The front pinion bearing on disassemble was BAD, like REAL bad. Back one was pitted but not real bad. Carrier bearing races were "gray" no bearing pits or chips, axle bearing were ok, but.......
Dodge Dakota forum is full of stories of the bearings going.
9" diff. on the newer Dakota's also had problem from what I can read.
I believe it is a oil issue, as 75-90 can't "cushion" the bearings well enough, I dunno?
I debated what to use for oil after the rebuild, Amsoil or BG, but settled on Amsoil as I could not find the heavy duty BG oil.
I've used Mobile 1 in a few other "projects", never had a problem??
Diff temp today running 26 miles at 70 on highway at 25 degrees was 57 degrees.
I will change it after I tow up there as well as keep and eye on temps
Joe
 
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alldodge

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Hope you don't have anymore issues. 130K isn't that bad, but as you say I don't know. Never had a mid size truck, always 1500 and 2500. Had 160K on a 1500 with a 6 banger, use to pull a lot boats and other stuff, no issue other then need more power.. Since then have had nothing but Diesels. The history is good to know, thanks for sharing
 

NYBo

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Are you the original owner? If not, a PO might have done who-knows-what to the truck.
 

oldjeep

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Pinion bearing failure at 130K in a 22 year old truck isn't necessarily an indicator that towing caused it. Stuff wears out.
 

Tnstratofam

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I owned a 91 Dakota extended cab 4x4 with the regular v6 and towed everything from a 6ft utility trailer for a mower to a 16 foot flatbed filled with hay multiple times. I'm sure I pulled way above the actual towing capacity a few times around my dads farm. The truck had 119,000 miles on it when I purchased it from the original owner. He never hauled anything in it other than some camping equipment the whole time he owned it. The inside of the bed didn't have a scratch on it. I had both differential fluids changed as well as the transfer case fluid the first week I had her. I also changed the transmission filter and fluid myself that first week. I bought her in 2000 and traded her in 2008. She had 287000 miles on the odometer when I traded her in. The only other things I had to replace that weren't routine maintenance items were the headlight switch, and the computer the year I traded her. Everything still worked fine on her, and I've talked to the people who bought her from the dealership. They replaced the transmission year before last, and the battery since they bought it. The truck had 366000 miles on it when I met them, and it was still running strong. Other than the F-150 I currently have that Dakota was the best truck I've ever owned.

Sorry you had trouble out of yours. I think I got a good one, and other than outgrowing it I would have kept that one.
 

Lou C

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I don't know for sure what Dodge recommended for towing but for my 98 Jeep Grand Cherokee it specifically recommended synthetic 75w/140 gear oil in the rear diff. I have always used it in both and they are still fine @ 157,000 miles. No long distance tows but towing boats up very steep hills.
For my 07 Grand the manual recommends the same thing.
 

Scott Danforth

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I abused my durango and towed at or above the towing capacity often. The issue is simple, the rubber plugs that were used on the diffs vs a real plug seep a bit of oil, eventually the level goes down. did you measure how much oil you pulled out when you changed oil at 132k? which by the manual should have been changed every 15000 miles. Did you follow the correct process for filling? some of the dodge diffs you fill to the plug, some you fill to about 2" below because they raised the plug point to prevent the oil seeping.

Also there is a TSB from dodge on over-filling causing oil frothing which may also take out the bearings.
 

alldodge

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Don't know when Dodge started but my 08 2500 uses Dexron IV in transfer case and differentials
 

WIMUSKY

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I "believe" the newer RAMs recommend every 60k. I do it more often since I plow. Not sure about the older stuff. Had a '93 chev that I changed around 160k. I had bought it new.
 

joetheis

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I hjad changed the oil before I towed the 250 miles.
I BELIEVE the Mobil 1 75-90 HELPED the bearing break down.
It was just funny when I went to the Dakota Forums, it's littered with pinion bearing failures, most were told by dealer, (I worked in a Chrysler dealership fro 20 years, trust me they are not "Know it ALL Gods", many tech are not the brightest bulb in the box!), that towing or heavy loads caused the failure.
The oil was full when I took the cover off, no rubber plug leak or seal gone bad, (I check my truck all the time- the anal mechanic)!
I see LOTS of these trucks on the road, so I can't believe all I read on the net.
Just food for thought, something to look at before heading out.
Joe
As always take any advice I give with a beer er 2!
 

bspeth

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That's a good axle to work on if you had to pick one.
 

alldodge

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My 09 Ram 1500 uses gear oil in the diffs.

Go figure, 2500 and 3500 get Dexron and 1500 and under get gear oil. Got me scratching my head on that one. Mine are Dana 60 full floating axles
 

Scott Danforth

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that does not make sense at all. if it was me, I would be running 75w90 synthetic vs ATF in the diffs
 

alldodge

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that does not make sense at all. if it was me, I would be running 75w90 synthetic vs ATF in the diffs

Well when the manufacture says ATF then I use it. My guess is Dana is the one which tells them what to use.

Had a 92 Ford Festiva (KIA) which used ATF in the manual 5 speed and transaxle.
 

oldjeep

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that does not make sense at all. if it was me, I would be running 75w90 synthetic vs ATF in the diffs

Makes plenty of sense - I remember when they went from Gear oil to ATF in gear drive transfer cases - no changes to the cases at all but the atf creates less drag.
 

joetheis

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That's the reason I went to Synth Mobil 1 gear oil 75-90.
I'm not too hip about using ATF in anything "gear to gear".
ATF is hydraulic fluid with lots of detergent. Gears (in my brain anyway), needs the "cushioning" of gear oil, (as well as bearings).
Trans/transaxles need ATF, cuz many have no seal between them, the trans pump pumps fluid into the pinion/carrier area, so it has to be one fluid, (years ago Chrysler tried to put a seal there, but it'd go bad and the pump would suck the fluid out and bad things happen.
We'd rebuild it and leave THAT seal out!
I remember running my old jeeps with dino oil in the diff and trans., and it was like the brakes were on when it was COLD out, til the gear oil warmed up.
Weird, the bearings were toast, low mileage on the gear oil.
Only thing I did was haul 220 er so miles.
I'm going to keep track of the diff. temps when I haul it up this year (Amsoil 90-150 with BG LSD additive on fresh bearings).
As well as my buddies Toy with Mobil 1 in his diff.
I'm posting temps on the Dodge Dakota forums, just as a template for anyone thinking like I was about temps.
Was it Dodge design flaw (lots of posting about pinion bearing going south), or oil break down?
The world wonders.
Joe
 
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