'05 Tacoma transmission issue/question

My BIL has an '05 Tacoma 4.0L 4wd 5 spd with ~110,000 miles on it. He DD's it into Denver from the foothills and they use it with a slide in camper for extended camping/skiing/hiking adventures around the PNW. About 18 months it started popping out of 4th gear when accelerating and while he know the transmission will have to come out he is wondering if they can HD the pertinent wear items to make them last longer. With the camper in he uses 4th a lot which could be causing the extra wear.

Anyone know any options on this?

A good high-quality gear oil might slow the wear, but there's no way to band-aid-fix the gear popping if it's caused by actual gearbox problems (which for a non-linkage-shifted gearbox, is almost certainly the case).

I got that. What I was asking is there an internal upgrade possible to the gearbox to guard against this failure happening again after the rebuild. Heavy duty synchros, hardened gears, etc...

I know my truck 1994 is older but there is was a shift ball joint bushing at the end of the gear shift that disintegrated and caused all sorts of shifting weirdness. New ball joint and sleeve and back to normal.

Seems there are no HD internals available for this gearbox, so his best bet might be to get some treatment done on the replacements for the offending parts. Maybe cryo-treatment on the synchros?

Cryo treat, shot peen, and good oil is gonna be about all you can do.

It's weird that he wore it out that quickly, did he ever change the fluid? Looks like those call for 75w90 which should protect things very well unless the fluid should have been changed 50k ago, or it's getting insanely hot (200+F). Unless it's some sort of shifter issue keeping it from going in all the way he's going to need to tear it down and see what actually failed before thinking about parts.

It's extra weird because if he is towing in 4th gear usually, then transmission wear should be negligible. Torque is transmitted straight from the input shaft to the output shaft, bypassing the geartrain entirely. His wear issues will be related entirely to the synchro splines on the input shaft (4th gear) and the slider.

You could try doing this or that or the other, but throwing in a used transmission and running it is probably the most cost-effective choice. If you have to replace the transmission as a wear item every 30-50k, you're still doing better than if you were to rebuild it with questionably improved parts that may not actually solve any problems.

Alternatively, you could do what Jerico's founder did in the 1970s. He had an arm injury with permanent nerve damage that meant he could pull on the shifter pretty good but couldn't push. So he rigged up a really strong bungee cord to the shifter. He'd be able to pull the shifter from 1st to 2nd, and then he'd let go of the shifter and let the bungee pull the lever into 3rd.

Bungee cord holding the lever back in 4th is pretty cheap...

benzbaronDaryn wrote: I know my truck 1994 is older but there is was a shift ball joint bushing at the end of the gear shift that disintegrated and caused all sorts of shifting weirdness. New ball joint and sleeve and back to normal.

Care to elaborate as to how difficult this job was and what it entailed? I have a w series toyota trans that deas exactly this. It's fine if you shift it aggressively but if you shift it gently/normally, it pops out.

In reply to sesto elemento:

If he's talking about what I think he is the job is the same and very simple on most single rail RWD transmissions. Remove boot, remove shifter, change the bushings, reassemble.

This video is crap quality but quick and to the point, unlike most "How to (easy job)" videos on youtube.

https://www.youtube.com/embed/tcZusrWw2ao

Thats it, only trick was having to move the trans shifter a bit to install shift lever arm thingy.

Did you BIL put all 110k miles on it while using it for the camper, etc?

If so, then going with stock parts probably isn't a bad idea. By the time the trans gets to the point of jumping out of 4th there will be other things wearing out.

To help he can also look at dropping the final drive ratio. By dropping the gear ratio it will let the engine spin a little more, but reduce the load on the trans compared to the current arrangement.

In reply to jstand:

Good point on regearing, if it's loaded down often it will drive better that way anyways, all this is doubly true if it has oversized tires on it.

Though if this isn't just shifter wear I'd guess the problem is worn bearings, new quality bearings, good synthetic oil, and adhering to the severe service maintenance schedule will probably permanently fix that. The 2005 MY got a 6 speed in the manual V6 trucks, with single OD, so the direct gear is 5th, not 4th, which explains the weirdness of 4th popping out.

Yea, I did that with marlin crawler bushings and it did help shift feel but not the pop out.