rear diff limited slip
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Trailering
Joined: Jan 2004
Posts: 24
Likes: 2
rear diff limited slip
Started getting a shuttering feel on turns while towing my 5th wheel a few years ago, had around 75,000 miles on it. Changed my rear fluid to valvoline syn with a friction mod still had the same feel, so at 85,000 changed fluid to royal purple 75/140w with no modifyer and still the same feel, so is it possible that mine will never slip like it suppose to, and will this "not slipping" cause problems down the road. I now have 110,000 miles on it, and there is times I worry about it breaking the axle but have never heard of that happening.
Thanks for any replies.
2002 f-250 4x4 c/c 7.3
Thanks for any replies.
2002 f-250 4x4 c/c 7.3
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
I know this does not answere your specific question but I just ran a 30K mile test on Royal Purples 75W-140. After 33K the oil dropped down from a 140 weight to a 90 weight and the iron wear level was in the severe level at 2,910 ppm. Not impressed. The silicon contamination was from the gasket sealant I used to put the stock cover back on with. Since the analysis I changed to the Mag-Hytec cover and back to Schaeffer's 75W-140. I'll post another oil analysis after another 30K miles.
For your specific situation. If it is the differential making the shudder you could try changing the diff fluid again then adding 4 oz at a time of the frictioin modifier to see if the chatter/shudder lessens or goes away.
For your specific situation. If it is the differential making the shudder you could try changing the diff fluid again then adding 4 oz at a time of the frictioin modifier to see if the chatter/shudder lessens or goes away.
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
each time you changed the fluid do you notice alot of metal sludge on the bottom of the diff or particles suspended iin the fluid? You could send in an oil analysis to see if there is any problems going on.
Senior User
Joined: Mar 2008
Posts: 436
Likes: 1
From: Mass
a shuttering when cornering could also be driveshaft u joints going bad. in a straight line they can spin freely but when cornering they might bind up a bit an cause the shuttering and or squelling.
sorry but can't answer your original question but when i read it this was the first thing that came to my mind.
sorry but can't answer your original question but when i read it this was the first thing that came to my mind.
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
I know this does not answere your specific question but I just ran a 30K mile test on Royal Purples 75W-140. After 33K the oil dropped down from a 140 weight to a 90 weight and the iron wear level was in the severe level at 2,910 ppm. Not impressed. The silicon contamination was from the gasket sealant I used to put the stock cover back on with.
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Senior User
Joined: Mar 2003
Posts: 428
Likes: 1
From: Hot Springs Village, Ar
skeet, Find a parking lot, turn tight circle 3 or 4 times to the right and then do same to the left. This may correct the shudder. It has worked for me several times. Carroll
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Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
I have RP in mine. I had a similar shudder before the swap, only when it had been driven for many miles. Shudder is much reduced now to the point I do not notice it unless I really look for it.
Rich, we are buddies. If you want to impress me, put Schaeffers in, then run it. Then send it to Schaeffer's lab and tell them it was RP. I would be curious as to what they say then as opposed to a competitor's oil. Better yet, a sample of the RP to 2 different labs would have been a good comparison.
Again, not to offend anyone, but everyone who has been here for a while knows how I feel about OAs. All I am saying is if you have quality stuff in, and it is not working, you may have a mechanical problem. This does not take an analysis of the oil.
Rich, we are buddies. If you want to impress me, put Schaeffers in, then run it. Then send it to Schaeffer's lab and tell them it was RP. I would be curious as to what they say then as opposed to a competitor's oil. Better yet, a sample of the RP to 2 different labs would have been a good comparison.
Again, not to offend anyone, but everyone who has been here for a while knows how I feel about OAs. All I am saying is if you have quality stuff in, and it is not working, you may have a mechanical problem. This does not take an analysis of the oil.
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
All good points points and any test or comparison needs to be unbiased.
I will send in the results to RP and see what they say, as Chris suggested.
I will also send in the next sample to a different lab as Mike suggests. But if I mark a Schaeffer's sample as RP and send it to Schaeffer's they will know the difference because of the additives. Besides Karen is a class act and wouldn't snub any competitors product, she's post what the test finds. I called the lab and they ran the sample twice because of the high numbers. They run the test twice on any sample that comes up with abnormal readings.
Just like when I changed to RP I flushed & cleaned out the diff before adding then new fluid. SAmples will be much easier to obtain now with the Mag-Hytec cover.
I will send in the results to RP and see what they say, as Chris suggested.
I will also send in the next sample to a different lab as Mike suggests. But if I mark a Schaeffer's sample as RP and send it to Schaeffer's they will know the difference because of the additives. Besides Karen is a class act and wouldn't snub any competitors product, she's post what the test finds. I called the lab and they ran the sample twice because of the high numbers. They run the test twice on any sample that comes up with abnormal readings.
Just like when I changed to RP I flushed & cleaned out the diff before adding then new fluid. SAmples will be much easier to obtain now with the Mag-Hytec cover.
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
All of this may be true Rich, but we are not racing our trucks with fifth wheels either. Sorry, couldn't resist, as you cannot either. 
Can we all agree that our rear diffs begin to wear out from the minute they get used rolling out of the factory? It is a wear item, and will wear out. Now the reduced viscosity of the RP is of concern to me, but not alarming. Isn't 90 weight the norm for some other diffs? I bet the stuff is still good.
Can we all agree that our rear diffs begin to wear out from the minute they get used rolling out of the factory? It is a wear item, and will wear out. Now the reduced viscosity of the RP is of concern to me, but not alarming. Isn't 90 weight the norm for some other diffs? I bet the stuff is still good.
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
Yep 90W is used in many diffs. Besides a small amount of sludge at the bottom of the diff the gears looked good. When I took the sample that I sent in to the lab the color was no longer purple but brown.
My camper racing probably didn't help much either......
I can't help it, while towing the sweat spot starts after 2K rpm, plus I'm impatient
My camper racing probably didn't help much either......
I can't help it, while towing the sweat spot starts after 2K rpm, plus I'm impatient
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