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Manual tranny doing weird things?

I

indd

Senior member
I have a Toyota T-100 truck that I bought from the original owner (thing has almost 290K miles on it, original clutch!). I don't know why, but a few times I've had this truck over almost the past year when I'm stopped and trying to go, the above happens. I'm in 1st trying to get the truck to go, and all of a sudden BAAAAM!!! The stick goes into neutral, and I'm like wtf! Nothing weird happens afterwards as it drives fine .. goes into 2nd, all the way to 3rd just fine.

I know I've kind of worn the clutch a little bit learning how to drive this thing, but it still works fine most of the time. Any ideas what could be causing this? It's worrisome as it's a huge noise. I'm surprised the tranny just doesn't fall apart or something afterwards!
 
If you're lucky it's the linkage, if it's in the transmission itself, well, you're not nearly as lucky. By a long shot.

If the trans comes out, do the clutch and throwout bearing at the same time.
 
Synchro rings cause that exact symptom when
they fail. Time to rebuild the tranny. And with
that amount of mileage on it, while it is out, get
a new Clutch, Pressure Plate, Pilot Bearing, Throwout
Bearing and if it uses a Hydraulic Clutch Slave Cylinder
as a lot of Japanese cars do, it would pay to overhaul
both it and the clutch master cylinder. Also check and
if needed, resurface the flywheel (if it is scored, heat checked
or gouged)
 
You could probably get a good reman or overhauled tranny for cheap (maybee 3 to 7 hundrend). Manuals aren't that expensive. It's just a gear box.
 
I was hoping it would just be something with the shifter as someone said.. but turns out maybe a full rebuild wouldn't be that bad.. at least compared to a automatic. The clutch and CV joints were going to have to be done too, so I guess all that could all be done at the same time. I want to drive this thing to half a mil so will do what it takes..

For now I think I'm going to try to just drive it.. the problem has happened about 4-5 times in the past 8 months, so if something's going bad then it's taking a while to go out. I figure it will get much worse as things get more worn..

Thanks to all for the input!


 
If its only happened a few times over 8 months just drive the thing. It has 300k miles on it and isn't worth rebuilding. If it does start happening a lot then just start out in 2nd gear. Its a beater truck so just keep beating on it.
 
Actually, I plan on keeping the truck until at least half a million miles.. so maybe a rebuild would be in order. Or steppinthrax has a good idea there.. thanks for looking that up! A local guy has a wreck where he already scrapped the body and took the engine, but the rest is available.. would be about the same price as the tranny above but I'd get axles, wheels and lots of other stuff too 😛

My local transmission guy who did some good work for me before just said to keep trying to hang onto the shifter while going, and that the hand-force would overcome those forces causing it to boom. I asked him about the price of the rebuild, and he said it, but said that it should last for quite a while to come. This is the 2nd time he's told me something so I could avoid some mechanical work (sheesh!)..
 
I had a Honda that did that a few times, turned out to be a cracked motor mount. Was a cheap fix, and shifted way better all the way around afterwords.

Also had some motor mount wear in my 911 and replacing them made the shifting much better.

So I'd go after locating parts first, at least for an eyeball check. Motor/Transmission mounts, linkage as suggested before, etc.
 
Uhhh, the syncro for first synchronizes second gear, and it being damaged would cause a grinding when shifting into second, or popping out of second, not first. Is this a RWD only W56 transmission and is the shifter stock? My guess is a either a bent shift fork, or possibly an oil problem.

Have you checked the gear oil or changed it yet? I would start with changing the oil and start looking for a used transmission or buy a rebuild kit, the problem is, with a transmission that old it will need synchros and bearings, making the cost much more than just finding a junkyard one and crossing your fingers. Another advantage of buying the replacement one, is you could get adventurous and open the old trans. and try to diagnose the problem.
 
Always start out with the simple things first.

Change the fluid, make sure the linkages are to spec, check the motor and transmission mounts.. once all of those are determined to be in order, start focusing on the transmission itself.

A used one would be cheap and easy to put in.. You could probably find one for 150$. Even if it "only" lasted another 100k miles, that's cheap.

Also, is there something I'm missing here? Why would worn synchros cause the transmission to pop out of gear? Aren't they just to aid in shifting?

There are synchroless transmissions.........
 
Originally posted by: Eli
...
Also, is there something I'm missing here? Why would worn synchros cause the transmission to pop out of gear? Aren't they just to aid in shifting?

There are synchroless transmissions.........
Click to expand...

I kind of addressed this in my last post. The syncros can get worn enough that they will chatter so bad as to knock the trans out of gear, but this is usually very rare. Especially in first gear, considering the syncro ring syncs first gear with second.

Yeah, there are transmissions without synchros or "dog tooth" boxes available, and they are certainly stronger, but mostly for race applications. Considering any low-level primate could get a driver's license in the states with the right training, the complexity of operating a dog box would be well lost on any market that currently prefers automatics by a huge margin.

I think a lot of people do not realize that in modern transmissions, the gears are always meshed, and it is the job of the shift forks and synchros to change gears. The actual gears are already together, but the synchros slow down or speed up the shaft to allow the shift fork to engage the "meshed" set. The exception is reverse of course, which still uses a straight cut gear, and idler assembly.

If anyone ever has a chance to break down a manual gearbox, I highly recommend it. Very enlightening and makes the whole operation easier to understand, especially if you are a visual learner. The first one I ever tore down was a FWD, but it works pretty much the same as a RWD, with the exception of most RWDs having a more basic 4th gear, and FWD having the final drive in the same case.
 
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