93sc3005sp

i finished my clutch install today and went and bought new gear oil, i got rp synchromax instead of rp 75w-140 cause i thought that was too thick, i have the w58 btw and it hought maybe the synchromax might be too thin

Blizzy

iTrader: (-1)

I am using the 75w-140 in my R154. It is lovely. There is no doubt the transmission shifts more smoothly once it has warmed up. But, once it is warm, you can practically feel the protection it is offering.

For a mid to high mileage transmission that you intend to beat on, money can't buy a better gear oil than Royal Purple 75w-140 (in my opinion). I have received PMs from other forum members about it curing synchro grinds and super notchy shifting.

If you do not intend to beat on your transmission, and you instead primarily drive your SC as a commuter vehicle, I would recommend something lighter since the protection of the 140 weight tolerance is gratuitous and costing you additional smoothness, especially at cold start up.

StiCk3

iTrader: (5)

a lot of the people on this forum use GM synchromesh in their trannies so i dont see why the synchromax shouldn't work.

It's funny you mention this, i had the chance to put in this stuff into my trans last week, but the mechanic couldn't get the bolts undone. I might have a go at it this weekend either with 75w-90 or synchromax.

93sc3005sp

what is the viscosity of rp synchromax

93sc3005sp

i went and traded for the 75-140, my dad now tells me that with that thick of oil, the synchros wont work properly, im no tranny guru, so more more input would be apreciated btw i have the w58 for reference

DryBlaze

I just picked up 3 quarts of the RP 75w-140 and I'm putting in another W58 (since I blew mine) so I'll let you know how it works out. I have one concern is that the thickness of this oil, would there be any down sides when the weather gets cold?

Gunnar

I run 75w140 Royal Purple in my W58 and have had 0 issues from doing so.

TecnoSmurf

iTrader: (2)

I am going to switch for GM to RP. GM did nothing for me.

StiCk3

iTrader: (5)

going to do add the Synchromax in on saturday ($35 for 3 quarts ). I'll post impressions later next week. Wish me luck!

SCV8

I always used the gm fluid as an additive, never straight like everyone does.
Worked great.

Blizzy

iTrader: (-1)

I have done some reading on the Synchromax/Synchromesh fluids, and I figured I would share what I have found with the community...

In regard to viscosity, the Synchromax from RP is thin to very thin. Below is a list of oil viscosities at 100*C (in cSt):
7.7 - RP Synchromax
9.08 - Pennzoil/GM Synchromesh
10.0 - Mobil1 10w30
10.7 - Amsoil 10w30
15.7 - Pennzoil 75w90
16.4 - Redline 75w90
21.0 - RP 75w90
26.9 - Redline 75w140
33.6 - RP 75w140

Honda/Acura guys swear by Synchromesh. I do not blame them. It is great oil and very appropriate for Honda transmissions. For what its worth, Honda transmissions normally take 10w30 motor oil. Their transmission are designed with clearances to take a less viscous oil.

Our Toyota transmissions are built to take a true gear oil. Most every Toyota guy chooses 75w90 for use in their manual gearboxes. Notice the viscosity ratings of the 75w90 products on the list above (15-21 cSt). This is significantly more viscous than either Synchromesh or Synchromax.

I have seen a number of Toyota forum members on various forums using the Synchromesh and Synchromax oils with some levels of success. I have also read accounts of guys blowing out transmission seals from the lack of viscosity (or even worse...blowing the whole transmission).

For reference, V160 guys use Synchromax, and that transmission is a whole different can of worms. The new Corvette six speed transmission actually suggests ATF from the factory, and Synchromax is what those Vette guys are using as a Royoal Purple stock replacement.

I was once told by an extremely trusted Supraforums member that I have used for advice constantly, "Use 75w90 on an R154 if you are going to be driving the car normally. If you intend to beat on the car at all, go with a 75w140 for the extra protection." I passed this very advice onto Gunnar, and his W58 shaped up very nicely from the swap (and he has a 67mm turbo: normally a disasterously large turbo for a W58).

Can Synchromax or Synchromesh be used successfully in a Toyota application? In my opinion, I would only use either of these products if you lived in a cold climate and had Ecomodding in mind. The decreased hydrodynamic drag within the transmission might be able to milk you 2-3% in your mpg (similar to using a 0w30 engine oil).

But, an Ecomodder is not pushing his car like a Lexus coupe owner. For our purposes, a 75w90 or 75w140 is likely the appropriate choice, depending on just how often you beat on your car. For the average SC owner, I would go with 75w90. For the enthusiast driver, 75w140 is going to milk the most out of your transmission.

Following the advice of a Honda/Acura owner when it comes to gear oil is not wise as a Toyota owner. The Synchromesh that they swear by is too light of an oil for our transmissions. We require true gear oil, and the recommendation I have received to use 75w90 (or 75w140) seems like a good one.

93sc3005sp

thanks for all the info guys, i will be filling my w58 with rp 75-140 2morrow when i reinstall it ;]

StiCk3

iTrader: (5)

Well so far some of the notchyness has disappeared, but it does seem to get worse as the tranny warms up. After reading Blizzy's post, now i know why

As i was pouring the RP synchromax in i noticed it was a lot thinner than the original oil that i had drained out. It was nice and buttery smooth when the car was cold, but as it heated up i started to get some resistance going into the gears. I'll jump on with the rest of the 75W-140 bandwagon this weekend before i blow something up. Thanks Blizzy for the warning though!

turbosw20

I'm running rp80w and it's working great can't complain at all!

FUZION

iTrader: (2)

well if your boosted you would want 75-140w regaurdless correct?