Toyota FJ Cruiser Forum banner
1 - 5 of 5 Posts

· Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
Recently I changed to RP 75w90 Gear Oil and within 600k my manual transmission started to pop out of reverse and grrind (like it was almost in gear but not quite). I'd shift out and then back in and move a few feet before the problem repeated itself. Did some digging and found people referencing RP gear oil as not compatible with tranny in FJ (or Toyotas for that matter yet on RP site it says it's compatible and a recommended selection for Transmission, Transfer Case and Front/Rear Diffs).

Replaced oil with RedLine MT90 and it is better but not fixed. Engages fine but pops out when rolling back more than 10' at a time so have to engage and disengage truck to keep it rolling without popping out of gear. Super annoying.

Put in some SeaFoam to help clean out the RP and have had that in there for 2000k and is again a little better but continues to do this. Am going to change fluid again but looking for advice on what other potential issues this could be related to.

BTW I also installed a Marlin Heavy Duty Shifter Seats and with my Short Throw URD shifter this made a radical difference. The OE shift bushing is very soft and it is difficult to tell when you are fully left or right to engage 1st/2nd or 5th/6th. This took a while to get used to but is far better. I used to have to push hard into 1st every once in a while but never reverse which has been consistent in shifting since I got the vehicle. Also when installing the new teflon bushing on shifter I noticed that the ball that inserts into the transmission to change gears is somewhat loose on shift lever. Wondering if this is perhaps an issue.

Considering that every 'Yota tranny I have had has been bulletproofe I find it really hard to believe that with under 200k that I have to rebuild my transmission. I think that's highly unlikely and can't see a shift fork or something of that kind being an issue. Could RP be so slippery that it's still affecting the gear engagement?
 

· Premium Member
Joined
·
5,240 Posts
No expert but if you used an non-compatible oil, bearings, thrust bearings, synchronizers, and shift forks might have went through some undue wear/stress.

Look up how a manual transmission works on YouTube and it can help you understand how the different shafts and gears works inside a manual transmission.

Poping out of reverse would mean that either those gears are not fully engaging, shift forks not pushing far enough, or the shaft is thrusting in the direction to let the reverse gear to disengage.
 

· Registered
Joined
·
6 Posts
Discussion Starter · #3 ·
One would think that they could trust an automotive lubricant's site to be true however I never had an issue before changing over to RP in my tranny and the problem replicated itself within 600 k of making the change. Removing the fluid and changing back to Redline MT has helped; however, it's not "fixed" yet that's for sure.

 

· Registered
Joined
·
121 Posts
It might not be of any great help at the moment, but I've been very happy with the shifting action after changing to Pentosin MTF2 75W-80 in the transmission.

Best of luck!
 

· Premium Member
Joined
·
2,313 Posts
Not to pop anyone's bubble here but when any manual transmission pops out of gear the oil has absolutely nothing to do with this problem. When this happens either the linkage is obstructed (rare) or the gear in question has worn out. A worn shift fork or a worn slider or syncho hub can also cause this problem. Changing the oil might make you feel better :wink, but believe me the oil cannot help a failed metal part. Also while we are on this subject if your transmission is grinding into gear the first thing you should do is check your clutch fluid reservoir. If your fluid is gone then that's why you are grinding. A leak in the slave or master cylinder is what causes this problem.
 
  • Like
Reactions: Sparky of NWO
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top