Friction Mod in T2 Torsen

Tim.ocon · Mar 23, 2026

Im looking for a definitive answer on if I should be running friction Mod in my car after I install the torsen diff

I seem to be getting conflicting information from many different sources, some day its not needed but it can be used to prevent gear whine others say it should be used as it does actually help

flyhalf · Mar 23, 2026

I domin my oem torsen. Interesting to see what other say.

Tim.ocon · Mar 23, 2026

flyhalf said:
I domin my oem torsen. Interesting to see what other say.

I didn’t think it will hurt anything to run it and you have proven that it won’t given you haven’t had it break yet loll

BackInBlack · Mar 23, 2026

What I was told was that the friction modifier helps with gear whine, but that it performs slightly better without it. My car is currently more of a daily, so I run with the friction modifier. I was also told that Ford puts it in there when they do it.

mwjscn · Mar 23, 2026

Same as above, what I've read is that it reduces noise at the cost of some TBR. You can always fill it with gear oil that doesn't have friction modifier, try it, and if you think the noise level is too high just suction out some with a flexible hose on a large syringe and add a bottle of friction modifier in its place. The 'definitive' answer, I suppose, is that the differential doesn't require it and adding any is up to user preference.

Tim.ocon · Mar 23, 2026

mwjscn said:
Same as above, what I've read is that it reduces noise at the cost of some TBR. You can always fill it with gear oil that doesn't have friction modifier, try it, and if you think the noise level is too high just suction out some with a flexible hose on a large syringe and add a bottle of friction modifier in its place. The 'definitive' answer, I suppose, is that the differential doesn't require it and adding any is up to user preference.

this is the majority of what I’m reading. I’m not worried about noise so I’ll get no mod

TA28 · Mar 23, 2026

Not needed it's a gear set up. But you need a very good full synthetic oil. As per kohr and old rehagen racing. Also call torsen they are out of Rochester NY. Decent tech line.
Yours is a 2.5 bias same as boss 302 and shelby units.
No clutch packs like posi
Chris

TA28 · Mar 23, 2026

In a full race car like mine fr500c noise I hear more from trans. T56. But when your spinning 5k or better you don't know. Or hear it . Because your more consideration is on driving

Dave_W · Mar 28, 2026

TA28 said:
But you need a very good full synthetic oil.

For highest Torque Bias Ratio, use a non-synthetic gear oil with no friction modifier. However, this may cause increased ring & pinion wear over a synthetic oil, so it's a tradeoff. Friction modifier reduces the stick-slip "chatter" of the gears in tight turns at low speed (e.g., parking lots), so Ford puts it in for NVH.

In a solid axle application for autocross or a couple laps in time trial, I'd go for the highest TBR and run a dino-based 75W-85. When temperatures start to become a concern -- full session HPDE, racing, any IRS outside of a/x -- I'd run a high-quality synthetic 75w-140. In either case, I'd leave out the friction modifier.

"Essentially, anything that reduces friction in the diff reduces its locking characteristic."

Torsen® Traction

torsen.com

"Because the ring & pinion final drive gearing are constantly running, they are a lot fussier regarding proper lubrication. So, your best bet is to seek out the recommendation of the ring & pinion manufacturer."

Torsen® Traction

torsen.com

"Essentially, the heavier, thicker, or more viscous that the oil is, the better it lubricates (generally). It leaves a heavier film adhered to the surfaces being lubricated. This reduces friction. But, that means that a differential operating in 75W-140 oil will have fractionally less locking effect than the same unit operating in 75W-90. This difference is not night and day – the changes are subtle. But if you’re fine-tuning a race car, it does offer one more knob that you can turn. By the same token, lubricant formulation and additives used have a similar bearing on the matter."
"Generally, synthetic lubricants have lower friction properties than conventional, non-synthetic oils do. Synthetic lube may still be preferable if the duty is severe or high temperatures are a concern. Synthetics typically offer superior performance in those areas due to a more durable molecular structure."

Torsen® Traction

torsen.com

flyhalf · Mar 28, 2026

Dave_W said:
For highest Torque Bias Ratio, use a non-synthetic gear oil with no friction modifier. However, this may cause increased ring & pinion wear over a synthetic oil, so it's a tradeoff. Friction modifier reduces the stick-slip "chatter" of the gears in tight turns at low speed (e.g., parking lots), so Ford puts it in for NVH.

In a solid axle application for autocross or a couple laps in time trial, I'd go for the highest TBR and run a dino-based 75W-85. When temperatures start to become a concern -- full session HPDE, racing, any IRS outside of a/x -- I'd run a high-quality synthetic 75w-140. In either case, I'd leave out the friction modifier.

"Essentially, anything that reduces friction in the diff reduces its locking characteristic."
Torsen® Traction
torsen.com

"Because the ring & pinion final drive gearing are constantly running, they are a lot fussier regarding proper lubrication. So, your best bet is to seek out the recommendation of the ring & pinion manufacturer."
Torsen® Traction
torsen.com

"Essentially, the heavier, thicker, or more viscous that the oil is, the better it lubricates (generally). It leaves a heavier film adhered to the surfaces being lubricated. This reduces friction. But, that means that a differential operating in 75W-140 oil will have fractionally less locking effect than the same unit operating in 75W-90. This difference is not night and day – the changes are subtle. But if you’re fine-tuning a race car, it does offer one more knob that you can turn. By the same token, lubricant formulation and additives used have a similar bearing on the matter."
"Generally, synthetic lubricants have lower friction properties than conventional, non-synthetic oils do. Synthetic lube may still be preferable if the duty is severe or high temperatures are a concern. Synthetics typically offer superior performance in those areas due to a more durable molecular structure."
Torsen® Traction
torsen.com

Another notes on the thicker oil, is that a thicker oil yes sustained better higher temperature, but on the other hand being thicker will create more Heat. Also following the thinking of going thicker that modifies slightly the function of the differential, a friction modifier may and I repeat May counterbalance that effect with a difference oil not only reducing friction but most of the modifiers, i. E. Motorkote comes with metal protectors. I have used motorkotr in the past on my OEM person with good success. I have videos of oil coming out extremely clear. And zero metal residue.
Just another thought

Paul McWhiskey · Mar 28, 2026

Flyhalf is right about higher viscosity gear oils not carrying heat away from the gear faces as well as a lower viscosity gear oil. The lower viscosity will flow better creating better heat transfer away from the gear faces. However, if the load and speed are high the higher viscosity may help to protect the gear faces better. The choice is yours. But, it is also wise to listen to experience and there is that in abundance here.

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Friction Mod in T2 Torsen

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