Aisin AR-5 5 speed oil (sometimes it grinds)

[2000Trooper]

the manual says to use engine oil in the trnas. For a while I used mobil 1 synthetic and the thing shifted beautifully. Almost no effort. I had always wanted to try redline or amsoil so I decided to go with the redline MTL over the amsoil synchromesh. The shifting improved, but i didnt think it was worth the extra cost. But whatever, atleast it will last a while. I recently went on a wheeling trip and I noticed that shifting between 1st and 2nd would somtimes be difficult, and at times it would even grind. Of course the clutch was all the way in and I had bled it pretty [censored] well prior. This was on a hot day in south carolina, going at slow speeds. I never have this issue on the road just on the trails. I'm curious to whether the MTL is too thin for offroading or if the clutch is not disengaging properly and it grinds in 4lo due to the higher torque.

 

[Kool1]

Sounds like the synchros are wearing. Shifting between first and second is the most common shift and usually the first synchro to go bad.

 

[2000Trooper]

Well the thing is that it only happens in 4lo. 4hi and 2wd(same reduction as 4hi) are fine

 

[IndyIan]

The trans doesn't know if you are in 4 hi or low, but off roading you are doing way more 1-2, 2-1 shifts that aren't close to rev matched, than you would on the street.

 

[aquariuscsm]

What kind've car is it (unless I missed it). Some people have had success using Pennzoil Synchromesh in a worn and/or finicky manual transmission. Or maybe just go back to your previous fill of M1 and see if your transmission is happier.

You said you have Redline in there now. I was reading up on manual transmission fluids the other night and some say Redline doesn't *last* as long as some fluids and that shifting quality will begin to degrade. Wonder why?