80W-140 and Torsen Biasing
- Thread starter Dominic
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No it should not but if any, it would be very slight due to frictional resistance between the gears. The Torsen differential is a purely mechanical device; it has no electronics, clutches or viscous fluids.
The Torsen (from Torque Sensing) works as an open differential when the amount of torque going to each wheel is equal. As soon as one wheel starts to lose traction, the difference in torque causes the gears in the Torsen differential to bind together. The design of the gears in the differential determines the torque bias ratio. For instance, if a particular Torsen differential is designed with a 5:1 bias ratio, it is capable of applying up to five times more torque to the wheel that has good traction.
The Torsen differential may be designed with different bias ratios ranging from approximately '2.5:1' to '6:1' or higher. This may be accomplished by varying the side gear helix angles, or by altering the friction characteristics for the primary components. An increase in helix angle increases the thrust component of the side gear meshes along the axis of the side gears so that smaller portions of the loads communicated by the side gear meshes are related to rotation of the side gears. In addition, the higher thrust component along the axis of the side gears increases frictional resistance at the end faces of the side gears which opposes side gear rotation and thereby further contributes to an increase in bias ratio.
A good example of the Torsen..
The HMMVV, or Hummer, uses Torsen differentials on the front and rear axles. The owner's manual for the Hummer proposes a novel solution to the problem of one wheel coming off the ground: Apply the brakes. By applying the brakes, torque is applied to the wheel that is in the air, and then five times that torque can go to the wheel with good traction.
Thanks bob, I know all about the torsen and most all limited slip differentials in general. I even wrote a differential guide for the V6 Fbody community (and whoever else wanted to learn) as a general guide explaining the uses of each differential.
http://angelfire.com/my/fastcar/diffey.html
Thanks though.
http://angelfire.com/my/fastcar/diffey.html
Thanks though.
MolaKule
Staff member
Domonic,
I attempted one time to purchase the Torsen for the '86 Burb, but it was
expensive.
Have they lowered prices any?
I think it is as revolutionary as the Wankel.
Let's see Now, my next car will have a three-rotor Wankel, a Torsen differential, a..........
I attempted one time to purchase the Torsen for the '86 Burb, but it was
expensive.
Have they lowered prices any?
I think it is as revolutionary as the Wankel.
Let's see Now, my next car will have a three-rotor Wankel, a Torsen differential, a..........
One problem I have heard it has though is strength. AFAIK, CART and F1 and other racing uses clutch pack style because of that. But I don't think any of us are pushing 900+hp, so we probably dont have to worry about that
The torsen can and will break if you stress it past what its designed for - a clutch based one will simply burn itself to pieces... So in that sense clutches are better, but changing clutchpacks every 40K on your hotrod isn't what I call fun.
You can buy a GM 7.5" torsen, just the basic model (which is pretty durn good for most people) for $99 from SLP. It fits all the GM 10bolts.
http://www.slponline.com/view_product.asp?PARTNUMBER=64501T
You can buy a GM 7.5" torsen, just the basic model (which is pretty durn good for most people) for $99 from SLP. It fits all the GM 10bolts.
http://www.slponline.com/view_product.asp?PARTNUMBER=64501T
Dominic, I have a 1999 Chevy s10 Blazer with the optional 'locking diffeerntial'. Is this the torsen unit or the purely locking unit you describe in your article? Also, does anyone know what kind of gear oil to use in this unit? The owner's manual specifies a GM part number and 80W-90 oil. I was thinking of getting some Redline Gear Oil but am not sure if I should get oil specified for limited slips or avoid any friction modifed gear oil. Your advice would be appreciated.
Actually if your rear differential is a locking differential that can be manually actuated using outside hubs or a control switch on your dash its not the same locker as I describe. The powertraxx unit I describe is a cheap way to make an open differential a locking differential, and sadly its either locked or open - no limited slip.
Your unit luckily does not lock unless you tell it to (using the outside hubs or electronic switch). Also when its locked the axles cannot turn different speeds, this is why the owners manual probably tells you to never drive the vehicle on normal dry pavement with it locked correct?
I'm sure a good redline or schaeffers 80W90 would work well in it. If you tow with it change it every 15,000-30,000 miles... I think GM used to spec 15K as the interval for heavy duty use.
Your unit luckily does not lock unless you tell it to (using the outside hubs or electronic switch). Also when its locked the axles cannot turn different speeds, this is why the owners manual probably tells you to never drive the vehicle on normal dry pavement with it locked correct?
I'm sure a good redline or schaeffers 80W90 would work well in it. If you tow with it change it every 15,000-30,000 miles... I think GM used to spec 15K as the interval for heavy duty use.
Molakule, I run a 7.5" 10 bolt Torsen with my 430 rwtq Camaro. I run street tires (G-Force) and the Torsen has been fine so far.
MolaKule
Staff member
Carl,
It would certainly be educational to see the iron (wear) levels of the Torsen after say 15K to see how it compares to conventional differentials. The analysis of the torques and forces on the various gears in the Torsen is an interesting but complicated exercise.
It would certainly be educational to see the iron (wear) levels of the Torsen after say 15K to see how it compares to conventional differentials. The analysis of the torques and forces on the various gears in the Torsen is an interesting but complicated exercise.
Dominic, sorry for the lack of clarity in my previous post. The vehicle is 2WD and the 'locking differential' is not controllable from inside the SUV. The option sheet for the SUV says G80 Locking differential for an extra $280. Is this a limited slip variation or true locking differential? I imagine the answer should dictate what kind of gear oil I should use(ie, with or without friction modifiers).
Forgot to mention....it also is not controllable from outside the vehicle. There are not hubs to turn or switches in the cabin. The owners manual says it locks at certain times by iteself to improve fuel milege and for traction reasons. Again, the option sheet says G80 locking differential. Do you know what this really is and who manufactures it?
so, is this a limited slip unit? if so, why do they call it locking? lastly, what kind of gear oil should i use? limited slip gear oil or one that has no friction modifier in it? thanks...
one more quesion please. I looked throught the Eaton site and they say the G80 RPO code for Chevy and GM light trucks and SUVs is their limited slip locking differential. Are you sure my unit is the Torsen brand? How can I tell? This is all very confusing...
Molakule, I should have added the Torsen rear has 125,000 miles on it. 55,000 w/ the factory 305 h.p. motor, 55,000 miles w/ a 425 h.p. motor and 15,000 with my current Hi -torque 396 c.i., 465 h.p. motor. I just changed my gear oil. It had about 13,000 miles on it. I was very impressed w/ it's "visual look".
It was Redline's Heavy Weight Shookproof gear oil. This was the first time I've used this gear oil. It was pink and thick going in, and coming out 13,000 miles later. It did not darken. When i drained it from my clean pan, after sitting for 24 hours, I always see little metal particle on the bottom of my pan. There was absolutely no metal particles! Perhaps i can send off a sample and see if Terry can do an analysis of it???
I want to make sure I didn't contaminate it by putting it into a different container.
The G80 in GM SUV's is NOT a torsen. It is an Eaton gov-lock. Although it's called a locker it actually has clutch packs in it.
MolaKule
Staff member
Carl,
If you do send Terry a used oil sample you might want to send in a virgin sample at the same time. The starting and ending TAN values are important to drain extensions.
If you do send Terry a used oil sample you might want to send in a virgin sample at the same time. The starting and ending TAN values are important to drain extensions.
Given that the G80 in my SUV is an Eaton gov-loc, what kind of gear oil would everyone recommend. Again, the manual says 80W-90 but does not specify whether to use one with or without a friction modifier. I am guessing that since it has clutch paks in it, it should(?) use a friction modified gear oil. Thanks again...
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