Transmission Fluid Additive

You might try Swepco. Of course, based on personal experience.

Results may vary.

We have tried FORD additive, but only on F-150's.

Regards, Alberto

 

Can someone explain “limited slip additive” making transmission shifts smoother ?
And while at it, what’s the point of such additives in positive traction final drives if/when they tend to make the friction less effective ? Seems counterintuitive.
Just curious.

 

The friction modifiers help the synchros grab/engage. I think it can be thought of as increasing friction when the oil is in shear (as in synchros), while still lubricating the meshing gears (which is primarily the oil in compression).

 

Greg: Timo is correct, the "friction modifiers in Limited-Slip (LS) additives make oil MORE slippery. They do not increase friction. Their purpose to to allow the limited-slip clutches to overrun more easily when the car turns corners and the two rear wheels rotate at different speeds. LS additives do not help synchro action, as the synchronizers do need friction to operate correctly. It is all a very delicate balance within a transaxle that includes a limited-slip differential.

 

Gotcha, thanks for the insight! So are there LS additives and separately other types of friction modifiers that *do* increase synchro friction? To the point of the OP, if the LS additive reduces friction for reasons stated, then it seems like the synchros would be *less* effective… also just for another datapoint, I am running MTL which did show a marked improvement in synchros compared to whatever was in there prior, but I will still get a 2nd gear grind if I rush it. I would be curious if anyone has experienced both MTL and Sepco. (Tho I don’t mean tk hijack this thread, and there are surely many others that talk about this and I did not do a search so feel free to ignore given my poor form!

 

Greg: Oil choices are very personal tings. I know people who have great success with Swepco and people who hate it. I had no success using MTL in a Daytona. It was definitely more difficult to shift and it caused the limited-slip clutches to chatter on corners. Personally, I have had success using Mobil 1 75/90 in Ferrari transaxles. Others can add their experiences.

 

This article has a good description of "Friction Modifiers" and how they work:

https://www.machinerylubrication.com/Read/30336/friction-modifiers-use

I'd summarize it to say that the intent of friction modifiers is not always to just be more slippery, but to provide a more consistent friction amount between surfaces when those surfaces are moving (shearing) at different velocities -- i.e., to make the static coefficient of friction and the dynamic coefficient of friction more equal so that things "slip" more consistently at all speeds (even when going from zero speed to some non-zero speed) rather than doing a start-stop-start-stop action. But it is a lot Black Magic with wildly variable results .

 

Redline knows this exact and is why they make 75/90NS, read their explain
https://www.redlineoil.com/75w90-ns-gl-5-gear-oil

"75W90NS GL-5 GEAR OIL

• Designed for transmissions and transaxles - helps to slow synchros for easier shifting across a broad temperature range
• Popular in Ferrari, Porsche and Subaru transaxles
• Muscle Car applications like Ford Top Loader, Muncie transmissions, Borg-Warner T-10 and Super T-10
• Contains extreme pressure additives like our 75W90 GL-5 oil, but lacks friction modifiers to balance slipperiness
• Improved copper corrosion protection to prolong synchro life
• Helps with lock-up on weak limited-slip differentials-compatible with Red Line Limited Slip Friction Modifier for tuning slippage
• Also used with clutch-type LSDs in racing for maximum lock up
• Recommended for API GL-5, GL-6, MT-1, MIL-L-2105E and SAE J2360
• Non corrosive formula, safe for use with all synchro materials "

I removed new look Valvoline 75/90W and replaced with REdline 75W90NS and it shifts like the new automobile for 246 Dino

i am surprised many have success with MTL, but happy is so