Archived Dana 70 Diff problem - no differentiation!

[Scollins]

I've been trying to diagnose a problem with my drivetrain over the last few weeks. I will get a popping and grinding noise when taking sharp corners under power. Tonight I decided to change my diff fluids, and check things out.



WELL, I took the rear cover off, and everything LOOKS OK. I've got a limited slip as well. When I turn one wheel, the other wheel turns in THE SAME DIRECTION! I expect this with a limited slip (as opposed to an open diff, where the opposite wheel should spin the opposite direction. ) Here is my problem: no matter how hard I try, I CANNOT get one wheel to spin independent of the other! Is the limited slip so tight that I can't possibly get it to break loose under human power? HELP!

 

[paccool]

The popping noise is not unusual with the type of limited slip that was used in our trucks. Grinding is another issue. I don't think you can spin just one tire by hand like you were asking.



I had to have mine rebuilt when the rear end was rebuilt. The friction clutches were shot. I had some chattering going on for a while before and feel that was why the heavy clutch pack wear.



How bad was the oil you drained out? was there a lot of shavings on the magnet on the rear cover? Replace that oil with a good brand (synthetic is best IMO) and put in at least one bottle of the Dodge limited slip additive. I tried a different brand and still had the chattering. Also, don't use Eaton synthetic, it makes the limited slip chatter real bad even with the additive.



Hope this helps

 

[Scollins]

I didn't notice any shavings in the oil. The oil looked OK, but it didn't have that really nasty smell that hypoid oil usually has. I don't have any of the OEM friction modifier, I bought some other brand at Schuck's. It will have to do for now, until I can get the OEM stuff.



Are clutches visible inside the diff carrier? I can't see any that I can identify. I don't think the previous owner put a locker in it. Also, around one of the spider gears, I noticed some heat discoloration in the case. Not much, but it bothers me... ... .

 

[paccool]

I don't recall being able to see the clutch packs. I had a pile of shavings on the magnet but there was some major wear happening on the gear set in mine. That was the main reason for rebuilding the rear end. Told the shop to look at the clutches and fix if it needed it. they saved the old ones for me and I was glad to have them replace the clutch packs after seeing the wear. Works smooth now, no chattering since I went with a good synthetic and the Dodge additive.



You need to put in 1-1/2 bottles of the additive if you use conventional oil. Royal Purple (what I used) and Amsoil say no additives needed but I wanted to be sure and put one bottle in.

 

[Evan A. Beck]

May want to check the gear backlash... It could be a bearing problem. I doubt it, but it's possible. Sounds like now is a good time to upgrade to a MH diff cover.

 

[Scollins]

Well, I've got fresh 85w-140 in there now (not synthetic, I didn't want to waste it if I have to pull it apart again soon. I also dumped in one tube of friction modifier. After the test drive, it seems OK, without the binding or grinding noises I was hearing earlier. It may have been the oil was wasted. I've got 115,000 on the ticker, and I've put on the last 20,000. Maybe it was the original fluid!



I'll keep an eye on it and see how it goes. I don't know what the backlash spec is, but everything seemed OK. I'd like to upgrade to a MH, maybe soon.

 

[paccool]

I know what you mean about not wanting to waste the oil. I ran mine after the rebuild for about 5,000 with the conventional oil the shop put in when the rebuild was done. I wanted to get a good lap in run on the new gear set. Thats when I drained and put in the Eaton. I left it in about 1000 miles until I could get the Royal Purple. I was getting tired of pulling the cover and cleaning up afterwards! I want to also go with the custom cover but don't want to fool with it for awhile. Spent too much on oil for now.



Sounds like the oil in yours went bad. Hope no damage was done to anything. Run it for awile and see if it stays quiet. If there is no gear mesh noise ofr chatteriang from the limited slip, then everything is probably fine.