Getting tranny and diff fluid tomorrow, what to buy?
 

I have seen many RP vs Red Line threads.

Is anyone better than the other, anyone break down sooner than the other, etc.???

I live in Dallas, TX, so its pretty hot, I want something thats gonna protect the tranny and differential.

So what has worked the best and what did you run in the tranny and the diff?

Redline MT-90 and 75W-90 synthetic. add some GM synchro mesh for smoother shifts.

So 75w90 for the diff and the MT90 for the tranny?

How much blend of syncromesh? I was considering running all synchromesh.

for the tranny in hot climates such as yours?--i used RP max gear(not synchromes stuff) 75/90 one quart and rp max gear 75/140 one quart. makes it much smoother and quieter. I have ran them all--and this is the one that worked best for me.
olddragger

+1 for Redline

As per one of the only guys around here I trust to talk about lubricants:

for the trans make sure whatever you get is GL-4 ONLY. Do not get GL-5 fluid.

Yeah I know the tranny is GL-4.

The diff. can use GL-5 though right?

Correct - GL-5 or GL4/GL-5 combo will work in diff just fine. 75W90 weight.

You do want a GL-4 only for the trans - I prefer no GL-4/GL-5 combo fluids as they will work, but are harder on syncros and soft metals (especially brass) used in trans and will wear them out quicker.

BG, Redline, Amsoil all make good GL-4 only products.

Kinda funny, but my mother was at the Honda dealer and remembered me saying I was gonna do some fluid change. She picked some Advanced MTL for me, gonna take a look at it.

Said some tech sold it to her saying that's all they use on the S2Ks. I havent seen much about it on the internet except for the fact that its pretty new.

GL5 is ok in the trans as long as it's the right type, it can't have any limited slip additives which many gear oils do

is that what you use?

I have:

but I currently use Shockproof Heavy, which does not have a GL rating that I'm aware of:

Sounds like a fluid that the change interval is much shorter than what would be used on a daily driven car.

I only made the change from 75W140NS to Shockproof Heavy because of the added gear teeth cushion effect. Both of the trans I broke prior to going to heavier fluid happened on hard 1-2 upshifts; blew all the 2nd gear teeth off of the countershaft. It seemed like the right thing to do ... and mine's not a daily driver, only 6000 miles in over two years. I change the fluids several times a year due to the severity of the useage ...

I use Mobile one for the syncros. No problem.

I've heard of problems with Synthetic in the rear end.

I also use royal purple 75w90 in the rear and 50-50 mix of 75w90 and 75w140 in the tranny. Tranny is quieter, but the 1-2 shift still takes longer to happen than I would like (all other shifts are quick.) The diff is now perfect . . . quiet, noticeably cooler, and smooth. I had binding issues on tight radius turns with the stock fluid.

I don't get it - the recommended fluid is 90w, why mix it with 140 then complain the shifts are slow?

I use 60% Redline90/40% Redline MTL for a thinner mix, and the shifts are snick-snick!

S

I though it was you doing the RL mix for trans!

Very good formula in my mind as they are both GL-4 only.

Not true.

While the LS additives are hard on trans as well - the main concern is the Extreme Pressure (EP) additives needed for diffs to meet the GL-5 spec - these EP adds are mostly very hard metallic adds that just kill the softer metals (brass, etc) used in most manual trans and will cause an increase in wear.

Well I was at Rotary Performance today and they dont sell RL or RP. Picked up two quarts of Idemitsu 75w90 for the diff.

I have 2 quarts of Honda Advanced Protection MTF that was given to me, its made by Idemitsu for Honda, or at least the bottle says so.

Problem is I dont know if its GL-4 or GL-5. Also, the bottle doesnt have a weight on it either? Think it is safe to run this?

Well I couldnt find any info about the weight of the Honda fluid. What I did find on a S2K forum is that this fluid is a new synthetic for 07', made by Idemitsu, and S2K guys online says it works great in the tranny.

Honda transmissions tend to used a lighter weight oils - probably 70W80 - an it would work, but just be OK. The BG Syncroshift II I use is the same weight and I am very happy with it, but it is in a different league than Honda fluids.

Honda's factory oils have met with mixed reviews on BITOG and are considered average at best - not because of Idemitsu, but because Honda's oil specifications are only average and they like to charge premium prices for them to achieve high margin revenue (including specifying to only use their fluids).

Honda MTF has been a dino oil, and this new bottle does not specify synthetic, so it likely is not, and I would stick with synthetics.

Personally, I would get something else - BG, RL, or Amsoil.

Not true on the fluids I posted, you're talking generalities, and that one is as old as my grandpappy ...

so what is the right oil? my manual says gl4 or gl5 for tranny and gl5 for the diff.

I might give the casrol synthetic 75w90 a try for both the tranny and diff., but it is gl5.

Apparently the owner's manual has changed. (i haven't gotten my hands on a new one though)

04 and 05 manuals stated GL-4 or GL-5 worked just fine but newer manuals only list GL-4.
My advice is to stick with GL-4