Chris Spiess

lot so of different stuff in this thread....

If you have a torsen rear the heavier fluid will actually increase the bias ratio of the differential. A good thing IMO if like the corners, but doesn't matter much for striaght line performance.
The use of synthetic or not is a matter of manufacturer recommendation - Auburn says no, Eaton says yes, Torsen say they don't care as long as it's GL-5. FWIW my 98 has an Auburn but GM says use only synthetic <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> The use of additive is mainly just for noise and chatter concerns in the clutch type rears. It actually causes a little extra slip so it stands to reason that it actually brings the bias ration down. My factory auburn was a bit on the weak, so when I changed axles a couple months back I just refilled with AMSOIL synthetic 75/90 and no additive, and it actually seems to have improved a bit.
Most synthetic gear lubes are now GL-5 rated - not all, but most and probably everything you're going to find at the autoparts store.

2001bird

I also just changed fluid along with some studs and a girdle. I used AMSOIL 75/90W. For vehicles with a Torsen Diff the factory recomends synthetic. I also used 4 ounces of limited slip additive. I believe Red Line fluid comes with a friction modifier already, so you don't have to use a additive.

OBSSSD

Will you lose any hp at all by running 85W-140 over 75W90?

mitchntx

iTrader: (14)

Maybe, in the cold weather.

patSS/00

iTrader: (6)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Chris Spiess:
<strong>The use of additive is mainly just for noise and chatter concerns in the clutch type rears. It actually causes a little extra slip so it stands to reason that it actually brings the bias ration down.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I justed changed mine using Redline 75W90, which contains additive (which I knew I didn't need, but figured it wouldn't hurt). So since I have the stock torsen type, you're saying it would be better to use lube that has _no_ additive?

AFTICA

iTrader: (8)

My 3.73's made noise with 75W/90 Amsoil Synthetic & the additive, so I tried Valvoline 85W/140 Dino oil with the GM additive & 90% of the gear noise is gone <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> On a daily driver, I will trade the 1 or 2 HP loss that you may experience for the quiet gears anyday.

Orange Krush

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by ShooterSS:
<strong> I'm going to install a T/A Girdle and I got some Redline 80W140, but I see that the 'norm' is 75W90. Is anyone running the 80W140 and if so, anything I should worry about?


</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I run the 80-140 without a problem in my Zexel-Torsen!
In the Zexel-Torsen unit higher viscosity fluid is better! <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

The thicker fluid increases the torque bias causing the "posi"tive <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" /> drive action of the differential to be even stonger! <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

http://www.torsen.com/products/products.htm

<small>[ April 12, 2003, 09:15 AM: Message edited by: Orange Krush ]</small>

SteveC

When I had my gears changed from 3.23 to 3.73, the shop perfoming the work used straight dino 140W for the break in period. They informed me NOT to use sythetic oil at all (I have a Zexel-Torsen). They also recommended that I use 85W-140 oil at my first change, for not only will it keep the gears quiet, it will also prevent searing of the gears, because it disapates the heat faster than thinner oil.

I purchased 1 gallon of Valvoline 85W-140 dino oil for my first change at 500 miles after the install, for $8.99 at Kreagen Auto Parts, and added the GM posi additive.

My gears are quiet, and I have no issues at all using 85W-140.

SteveC <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

MOTORCITYMADMAN

Just to let you guys know. American Axle makes the HD axles for Chrysler and they come with synthetic lube(no additive needed). Also, pre 03 HD trucks that came with the "towing package" specifies in the manual to install synthetic lube.

Point being that synthetic isn't just good for engines and trannies anymore. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

tmgxray

I use amsoil 75w90 series 2000 in my rearend and you don't need additive because it already has it. I use it in my Durango R/T(which is a 4x4) and Trans Am WS6. I have experienced no noise, plus better performance and gas mileage.

hope that helps

trackbird

iTrader: (4)

Somewhere around here I have an article about GM's development testing on the Corvette ZR1 at Talledega Motor Speedway. They were talking about ZR1's burning up rear gear sets at 180 mph in 15 minutes to 1/2 hr on regular oil. They switched to redline and had no more failures, they tried mobile 1 and had an occasional failure. They were also loosing (melting) Power Steering hoses and found that synthetic PS fluid stopped that problem. And....synthetic oil (redline or mobile) in the crank case lowered oil temps by 35-45 degrees. I'll have to go raid the garage and find the article...it was in an old Hot Rod I think.....This is why Corvettes (and Camaro SS) came with synthetic oils in them.

DinoZ

iTrader: (5)

I ordered a couple of qts of the Redline when I ordered my girdle and cap studs... how much oil should I have ordered? I think I only ordered 2, now that I think about it.

trackbird

iTrader: (4)

2 quarts should fill it just fine.