I've been reading up on how GL-5 rated gear oil has a higher sulfur content and can corrode the synchros even though the manual says you can use GL-4 or GL-5. A lot of people with shifting issues have said that Redline MT-90 or Royal Purple are good GL-4 oils that are made for helping your synchros grip.

Something else you can try is OVERFILLING your transmission. But only slightly, like a 1/4 quart (1cup). I read about it here: CURE NOTCHY SHIFTING! 3rd gen and taco - Page 2 - YotaTech Forums
My R150F transmission had pretty grindy shifting but I tried this just for shits and giggles and, to my amazement, overfilling it .25 quarts actually made a big difference! It still grinds, but noticeably less.

I recently got some of that Redline MT-90 gear oil that I'll be putting in soon. I'll let you guys know what happens.

Beat solution I have found is a 60/40 60% gl5 and 40% ATF 3
Cleans the fluid and parts also makes the fluid thinner so smoother shifting. Never had a tranny fail using this. And always nice clean fluid when I change it out!

I had that problem. I usually come to a COMPLETE stop then shift into reverse as i am letting the clutch out a little. this works most of the time. once i get it in i slam the clutch pedal down. it works but should be checked out.

Remember: Even if your wheels aren't turning, if your engine is turning then your tranny is turning.

That will only make a greater difference in speed between the input shaft and the reverse gear.

I agree with the above , reverse does not have a syncro so you need to be at a complete stop . Even the owner's manual says if you have a hard time going into reverse , put it in neutral , take your foot off the clutch , then push it back in and go back to reverse , that's pretty much just double clutching it . Mine likes to give me problems every now and then too , I more or less just ignore it , just chock it up to there being no syncro for reverse .

Hey I know this is unrelated to this specific thread but the site won't let me post yet because I don't have enough responses posted so - I haven't been able to check the transmission fluid on my 1995 4x4 manual 4runner with the 3L V6 because I don't know where the fill plug is or what it looks like. I haven't found anything on the internet about these transmissions; can anything tell me what this plug looks like and where it's located?

I agree. I used to have an Alfa Romeo that would grind when I put it in reverse. I always slippped into 5th first and then put it in reverse. Smooth as a school marm's thigh.

24mm on the driver's side. Not the hex key on the passenger side.

You likely have the R150F transmission unless someone changed it on you.

Toyota truck transmission identification – Core Shifters

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Hi also new member working on minimum post count. Got a '88 3.0L V6 (3VZE) and I honestly just have a really loud pinging/knocking when I'm in neutral. Recently refilled/replaced gear oil in transmission, transfer case, and rear diff and it has made no difference. Am I worrying over nothing or is this a serious issue?

Don't know if this needs to be said but it is a manual transmission.

grinding into reverse can also be due to an incorrectly adjusted clutch, ie its not disengaging all the way. Sometimes bleeding the system can solve that.