Transmission shifting difficulty after using synthetic oil Tacoma

[Tony H]

I installed Redline gear oil in my Tacoma 5spd thinking I was doing something good for my truck (71K mi). After a while I started noticing difficulty downshifting especially when cold. Didn't think about the oil. Started giving it some thought and wondered if the synthetic oil had screwed up the friction material on the synchronizers. Changed back to conventional oil-better but not like before. I'm thinking about one more oil change-there was probably some synthetic oil left. Downshifting into first is not possible unless almost stopped and barely moving.

[oldsinner111]

now they use to used 80w90 gear oil in manuals, I ran 75w140, because of mountains. Men got so soft they ran ATF for a while, but output,and input bearings suffered. My boy's manual 2017 mazda uses something like 30w. Younger breed are wussie's can't shift that 90w on cold mornings.Check before you buy, like automatic's to some need to slip, and some will short out electronic's with old stuff.

[Tony H]

It is 80-90. It's better when it warms up. I switched to synthetic because I was in a cold climate and I though cold shifting would be better.

[vwnate1]

DO check the manual as to what's specified ~ my 2001 Ford Ranger wants ATF and when I hot changed it with the correct fully synthetic Mercon IV stuff it began to shift mcuh better .

The old ATF I drained out was thinner than water and dead black ~ I bet it was original

I use synthetic oils in all my gearboxes, the vintage BMC boxes also want engine oil not gear oil and will grind themselves to death in short order if you fill them with any sort of gear oil .

[Tony H]

Manual says 80-90. The Mustang T5 I'm installing in my 3.5 coupe (probably same as your Ranger) takes Dextron lll.

[Sugar Bear]

Tony, I'm prepared for the snake oil comments...consider trying Lubegard gear oil supplement. It sounds like either the clutch or a synchronizer is worn.

When stopped does it shift normally into all gears except first?

Good luck!!!

[Autoputzer]

I sold my '92 Nissan Sentra SE-R to a friend at 104k miles. Somewhere around 150k miles, the transmission started being hard to shift. I suggested he change the fluid and put in Mobil 1 75W-90 fluid. It fixed the problem. I was on my second SE-R, a '96 badged as a 200SX SE-R. It was at maybe 50k miles, and doing fine. But, I put in the Mobil 1 and it shifted a lot easier. I sold it to my same friend at 127k miles.

[engatwork]

Be glad it did not have one of those newfangled CVT transmissions.

[vwnate1]

@ Tony ;

Yes, I'm sure it's the same box, I thought it was Mercon IV....(?) .

I only change it once a year and look in the book first to make sure I buy the right stuff .

As Sugar Bear mentions, it is critical that when parked with the park brake set, you can shift from first into reverse with NO CLUNK/GRIND ! .

If it crunches into reverse the clutch is dragging or the pilot bearing is dragging, both are easy fixes .

[Zulfiqar]

Originally Posted by engatwork

Be glad it did not have one of those newfangled CVT transmissions.

Those are a joy to take apart, almost looks like they thought of "how to design something to move the car in the most cheapest way possible" and you are just constantly laughing while removing stuff from it. (its usually straight up scrap even on the showroom floor too)

The countershaft sensor on those is "shimmed" - yes shimmed and you have to reuse the same shims it has if you are ever replacing the sensor.

Reason is that they made only 2 cases of the cvt, one for all 4 cyls and one for V6, the 4 cyl ones have different ratio sizes depending if its a note, sentra, NV200, Altima etc. - Yup, super duper cheap production. Almost all cases have extremely bad castings which you can see if you fancy tearing down one for some nice laughter time.

[Tony H]

I'm confident it's not a clutch problem(if it is a problem). I can shift into reverse no problem. Maybe it's just my perception but I don't remember not being able to downshift into 1st unless stopped/barely moving. Seems like I noticed it after installing synthetic.
I have tried synthetic in several manual/auto transmissions over the years and am not convinced there is any benefit over petro based. Engines and transmissions have totally different lubrication requirements so I can see it in an engine. If the transmission was designed to use synthetic of course. Ran petro in my last Toyota pickup transmission and went over 200k with no problems.

[Yankee1]

Originally Posted by Tony H

I installed Redline gear oil in my Tacoma 5spd thinking I was doing something good for my truck (71K mi). After a while I started noticing difficulty downshifting especially when cold. Didn't think about the oil. Started giving it some thought and wondered if the synthetic oil had screwed up the friction material on the synchronizers. Changed back to conventional oil-better but not like before. I'm thinking about one more oil change-there was probably some synthetic oil left. Downshifting into first is not possible unless almost stopped and barely moving.

I've used redline in both a 5sp manual tacoma (changed every 50k) and a manual BMW, the taco had 200k on it when I sold it and shifted like butter.

I'd say the fluid is not your problem unless you put the wrong flavor in, which is possible if you changed it out and saw some improvement?

[Zulfiqar]

I beleive redline makes a gear oil that is meant for synchronised transmissions - its different than their regular axle oil.

You are feeling the synchronizers not spinning up and down quick enough to enable a smooth gear change.

[Yankee1]

Originally Posted by Zulfiqar

I beleive redline makes a gear oil that is meant for synchronised transmissions - its different than their regular axle oil.

You are feeling the synchronizers not spinning up and down quick enough to enable a smooth gear change.

Redline makes the exact manual transmission fluid specified in the Tacoma's manual. No guessing required.

[Zulfiqar]

Yes, i think its called mt-90