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Hello, I have a question about my rear differential. I assume that the fill plug is the one that is on the cover, and when I refill, fill it to that plug. Is the drain plug the one that is on the bottom of the housing facing down toward the ground? Also, I tow a 5ver, around 11K, and was thinking of using the 75W-140 grape juice. Is it OK with the load I am pulling, or should I just stick with the 75W-90. I plan on sticking with the grape juice and maybe getting it from one of the supporting vendors. Thanks for the help.
 

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I has grape juice in it, stick with it if your happy. Others have used Mobil-1 also as a replacement.

I have Mobile-1 in the front diff, and Grape juice in the rear diff.

JJ
 

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"Yes" on location of fill and drain plugs.

The Fill level is a little tricky. I recommend you do a search and read all the opinions of others first.
When draining the rear diff most seem to only get between 2 and 3 quarts out (I got only 2.5 quarts).
If you fill the diff to the bottom of the fill hole it will take about 4 quarts.
So why the difference ?
Some say the proper fill level is 3/8-5/8" below the fill hole.
Some speculate that the factory fill is deliberately under to reduce the occurance of seal leakage.
Some say it is a consequence of leakage out the diff vent tube during assembly.
As for me, I just put in 3.5 quarts (to match the 3/8-5/8" fill level advice and seal leak speculation.)
I really recommend you do a search and form your own opinion.
 

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I just changed to Valvoline 75w90 full synthetic.Alot of people run this stuff and it's about $7.00 a quart.
 

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i just done both my trucks today. on the 05 i got about 2 1/2 quarts out and put 4 in which was not quite to the fill hole. gm says to use a little more then 3 quarts. i felt safer filling it to the fill hole or a little below. here is the strange part. the 03 dumped 5 quarts out and only took 4 1/2. again gm says a little over 3 but 5 came out from factory. i have always been taught that you should fill to the fill hole so that's what i done.
 

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Hello, I have a question about my rear differential. I assume that the fill plug is the one that is on the cover, and when I refill, fill it to that plug. Is the drain plug the one that is on the bottom of the housing facing down toward the ground? Also, I tow a 5ver, around 11K, and was thinking of using the 75W-140 grape juice. Is it OK with the load I am pulling, or should I just stick with the 75W-90. I plan on sticking with the grape juice and maybe getting it from one of the supporting vendors. Thanks for the help.
As long as it's not Welch's........................:badidea:
 

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Anyone use the Valvoline 75w-140 Full Synthetic? I've always been a sucker for Mobil 1 products, but the Valvoline actually looked like the better product in this case.....and specifically mentioned that it was for GM Limited Slip applications. It certainly wasn't cheap at ~$15/qt, but it beat the price on the "grape juice"...
 

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i paid 20 dollars a quart for the grape juice.
Was that a local "deal" or online? The best I've been able to do locally was $27.77/qt.
 

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$27 a qt? it's not aything but Syntheyic grease for gods sake. Not rocket science, just good old syn grease. Napa has the Valvoline Syn on sale foe $7,00 right now---
 

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Discussion Starter #13
What are everyones thoughts on using the 75w-140. Am I towing heavy enough to need it. Will it hurt me when I'm not towing? Like I said, my 5ver is around 11K. I tow it about once a month from March thru October.
 

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The 140 shouldn't hurt you at all. I had been "talked into" purchasing 140 for my 9.5" diesel Tahoe diff. Since I had it on hand, I put it in my DMax. I don't tow heavy or too often, but I ran the 140 for over a year and about 45,000 miles without a hiccup. When I drained it to replace with 75W90, it was clear and still looked like honey and I had very little metallic dust on the drain plug magnet. I was a little worried about running it in very cold winter conditions, but it never seemed to cause any driveline drag or problems with my G80 locker and obviously provided some superior lubrication. OBTW, it was Amsoil 2000 synthetic 90W140.

ON EDIT:
Just checked my records (dang! it's hard getting old and losing your memory - what was I talking about?) I ran the 90W140 one month shy of 3 years and 76,650 miles. Not a problem.
 

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Anyone use the Valvoline 75w-140 Full Synthetic? I've always been a sucker for Mobil 1 products, but the Valvoline actually looked like the better product in this case.....and specifically mentioned that it was for GM Limited Slip applications. It certainly wasn't cheap at ~$15/qt, but it beat the price on the "grape juice"...
I posted your answer a few rows up..:funnypost
 

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I'm going to change mine also (850 miles). I was told by the dealer I also need to add a limited slip supplement, but see no mention of that here. Does anyone use that? And if so what? Thanks!
 

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I'm going to change mine also (850 miles). I was told by the dealer I also need to add a limited slip supplement, but see no mention of that here. Does anyone use that? And if so what? Thanks!
The Eaton G80 locker requires no additives - only a GL5 rated synthetic lube.
 
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