Odd that TRE recommends against MT90 not having enough film strength protection compared to the regular 75w90/140?

 

Marshal said he was happy with MT90 when they had clutch front and that car sees a ton of ProSolo launches each year. Its worth the change to smooth out the clutch diff, if it does.

 

do the cocktail then, 2 MTL 1 MT90

 

our last transmission lasted 7 years of autox (which is give or take 1000 pro solo launches) on mt-90 (and it was a failed 4th gear syncro that took out the trans...). Road course work might need different gear oil but mt-90 seems fine for autox.

 

Even though Jon doesn't recommend it, I'm guessing he's got the fluid choices on there based on dealing with drag cars and making the gears survive. But before this trans I always ran MT90 too and the old clutch diff was silent. Totally worth a try.

 

why do you think the mfactory was silent? it's def not based on fluids. i flushed tcase, trans, and rear diff today with no change. oddly enough the trans had no shavings or anything in it, while the rear diff came out completely grey. I gotta pull the preload off the diff, it feels like a 2-way diff right now. with minimal preload shouldn't the wedge drive most of the clamping force anyway?

 

C7s are going for a steal right now even the Z’s because of how much mark up they had at first and then the market tanked. Tbh you could get away with getting a used one that wasn’t molested, that demographic is odd. Most of them were owned by old men that just let them sit in the garage.

The new A91 ecus are bricked from being tuned. This isn’t the first time BMW has done something like this, ran into the same issue on my e92 literally had to hunt for my specs with the build date that allowed for a tunable ecu.

I also often times toy with getting another car but then I look at how much money I just spent and how I’m pretty content with the evo being my toy and my job helps with any car itches due to the fact I drive a different car on the monthly basis.

I know I’ll never try to build a car during a pandemic ever again lol.

 

over here the gear fluid for diffs and gearboxes with plate diffs is marked as LS... i.e. 75W90 LS. Normally I use motul 75W90 in my gearboxes and 75W90 LS in the ACD and diff... so was kind of wondering how the 5 speed will shift with 75W90 LS in the gearbox, since I am switching to plate front diff... I had some ideas about modding the front transfer to oil the front diff from the transfer and not the gearbox... but have no time for that now..

 

MT90 is a gl4 fluid. 75w90/140 is a GL5 fluid meant for hypoid gear sets. Hypoid gears put A LOT more load on the fluid because the teeth literally slide across each other. GL5 also typically has a slighty higher kinematic viscosity vs the same weight GL4. On top of having a lot more extreme pressure additives, it helps the gears live longer.

I switched to 75w90NS in my trans and shifts the same as MT90, but my straight cut 4th gear is quieter.

 

Thanks for that info.. I was worried that the LS fluid might mess with the shift quality. Will run an inline oil filter in the trans cooling circuit to get some of the plate diff material out of the circulation..

 

I'm NOT using LS fluid. It's NS fluid... as in No Slip. There are no friction modifiers added to the NS fluid. Which is what makes it safe for synchro transmissions.

 

ok, thanks for the info... I have yet to see a NS oil over here, hence the confusion..

 

NS = NON slip
LS = Limited slip
They are opposite.
It sounds like you don't want to use the LS fluid.

 

ok, but my plated front diff "asks for" LS fluid...

 

Well...that's a rock and a hard place lol. May end up having to use a cocktail of sorts to find a happy medium if the Tranny is indeed the fluid used in the front diff only. I thought it had 2 separate areas?