CaliAgents1688

I've had some very slight grinding issues going into 3rd as it doesn't happen all the time and the grind only occurs for a fraction of a second.

Around 37k miles, I drained out the oem stuff for RP Synchromax since that is what I used in my BMW with excellent results. Initially, the shifts felt very smooth however I was still getting the 3rd gear grind. A couple of weeks ago, I up-shifted from 3rd to 4th at high rpms and grinded fairly bad. This is when I decided to go home and do some research here on RX8Club for a fluid which is compatible with our tranny and has proven itself over the long haul.

I settled with GM Syncromesh + Friction Modified. Expensive stuff at about $14 a quart at your nearest GM dealer! I also swung by Autozone and picked up a couple of bottles of Pennzoil Synchromesh since every post I came across claim the two Syncromesh fluids are the same, just priced differently.

Once I got home, I found out that GM Syncromesh + FM is NOT the same fluid as Pennzoil Synchromesh (more viscous/thicker). Maybe everyone's referring to the non-FM variant which is cheaper. Just an FYI for everyone, there are two types of GM Syncromesh fluids.

Let's cut to the chase... shifts feel just as good as when I put the RP Synchromax in, however the 3rd gear grind is almost non-existent. Let's see how this stuff fairs in the next few hundred miles. It seems like Royal Purple simply might not be Aisin-friendly. However, in the BMW community we love RP fluids, or should I say the ZF gearboxes do.

05rex8

iTrader: (7)

You are correct, RP is not good for our trannies. Their motor oil is fine, however.

TrochoidMagic

[QUOTE=CaliAgents1688;2774555]I've had some very slight grinding issues going into 3rd as it doesn't happen all the time and the grind only occurs for a fraction of a second.



I settled with GM Syncromesh + Friction Modified. Expensive stuff at about $14 a quart at your nearest GM dealer! I also swung by Autozone and picked up a couple of bottles of Pennzoil Synchromesh since every post I came across claim the two Syncromesh fluids are the same, just priced differently.

Once I got home, I found out that GM Syncromesh + FM is NOT the same fluid as Pennzoil Synchromesh (more viscous/thicker). Maybe everyone's referring to the non-FM variant which is cheaper. Just an FYI for everyone, there are two types of GM Syncromesh fluids.

can you be more extensive with the details?

which fluid seems thicker? which actually is?

and for the GM synchromesh, does it state the viscosity?

can you also give some info on the different one stating synchromesh+FM?

i currently picked up the pennzoil synchromesh, and that should be the same fill as the one GM uses. unless they ALSO have a different formulation... the synchromesh+FM??? in which i would like to know if it has a different (thicker) viscosity...

thanks, and keep us posted on your impressions of the fluids.

oh, which one are you on?

CaliAgents1688

[QUOTE=TrochoidMagic;2774779]Sorry, should have been more clear with my post. The RX8 is using GM Syncromesh + FM. I have a beater CRX Si and that one is using a blend of GM Sycnromesh + FM and Pennzoil Syncromesh. They only had 4 quarts on hand and I usually use a quart to flush out the transmission of the old fluid. Hope this helps.

TrochoidMagic

^^thank you.

well hopefully soon i will try out the pennzoil's synchromesh, as i wanted to have a thicker fluid in there...

but let us know how things are with the GM+FM stuff as i may want to blend it in the future... or even go in to a GM dealer and talk to one of the technicians and see what weight rating their line of RWD vehicles are on.

hope for the best results on both...(crossing fingers)

rotary.enthusiast

I wouldn't recommend any of the fluids you've mentioned for use in our transmission. Synchromax/Synchromesh is a lot thinner than the OE fluid. It might shift a lot smoother now, but in the long run you could end up regretting it. I definitely wouldn't bang on it with that stuff in there.

kersh4w

iTrader: (3)

i love my redline mt90....

CarAndDriver

General consensus on here is to go with Redline or AMSOIL GL-4 fluids.

mazdaverx7

iTrader: (6)

this is all good research info i'm going to keep following this and see how this pans out. my question to the above is why go with GL-4 instead of GL-5?

alnielsen

iTrader: (4)

GL-5 is hard on the syncros.

rotarygod

Holy crap use the right product!!! RP Syncromax is the WRONG stuff!!!!!!! Do not use that in an RX-8 transmission! No wonder you had grinding issues. RP Max Gear 75W90 is what you want to use in the transmission and rear end.

If the people who say RP is not good for RX-8 transmissions have been basing their opinion on the use of Syncromax, no wonder you feel that way! You may as well use canola oil. Syncromax is good for Hondas and other transmissions that can use a motor oil type of lube that is much thinner. It is not to be used in transmissions like the RX-8's.

While there are other good products out there, I'll put RP Max Gear against any of them anyday and it will quite easily hold it's own and then some.

Jedi54

iTrader: (7)

RG is back!!!
Merry Christmas man

swoope

iTrader: (5)

wow,

so glad you are back fred. ran rp maxgear for 50k miles.. no problems.. go figure..

beers

ASH8

Tha MAN is in the House!..

Welcome Back Fred, sorry Rotary God!!!!, now where have you been?

We, well most of us missed you.

ASH8

BTW...RX-8
GL-4 For Manual Transmission.
GL-5 For rear Diff.
Both are 75W90

mazdaverx7

iTrader: (6)

^^ very good info to know. being new to these cars requires the right information when researching.

9krpmrx8

iTrader: (46)

Too lazy to search. How much of the RP maxhear 75W90 do you need for the tranny and rear end?

swoope

iTrader: (5)

4 qts.

beers

DOMINION

Good info to know. Now whos going to do mine for me

mysql

/me waits for the sudden influx of people needing new transmissions after reading the advice on this thread.

mazdaverx7

iTrader: (6)

what do you guys think of motul trans fluid?

zoom44

[ waits for mysqls advice ]

risky business

i just put synchromesh + FM in my tranny and it shifts like butter... its amazing stuff

Hi Flying 8

iTrader: (2)

Quote:

Originally Posted by mysql

/me waits for the sudden influx of people needing new transmissions after reading the advice on this thread.

Expand-give us your thoughts because many things have been suggested in this thread.

rotarygod

The first thing is DO NOT USE SYNCROMAX!!!! It's the WRONG product from RP!!!