Transmission falling out of third gear

Recently started falling out of third gear (128k, 5 speed, 2 wheel drive) and getting worse....... Synchros feel good no grinding in any gear....Shifter feels like it is fully engaging all gears equally....No main bearing or other noises.....but suddenly whether accelerating or cruising it occasionally just drops out of third gear only ( I don’t think it ever dropped out of gear on decelerating in third gear) any ideas before I buy a used transmission.

Worn third gear teeth only ?????

( I bought truck with 104k so I have no idea how previous owner treated transmission)

 

When it grinds going into a gear it's synchros, popping out of gear is THAT gear itself. Usually 2nd from too fast of 1-2 shift but 3rd is close behind. Sorry.

BTW it's not the entire tooth (teeth) that wear causing this. It's the leading edges from being jammed in too fast, causing it not to hold in place any longer.

I bet if you keep constant pressure on the shifter, it stays in gear?

If you know a trans. guy, you'll be better off (maybe) getting it fixed. Parts aren't that high and you know what you got.

 

Thank you for the confirmation.......I figured it was just worn third gear teeth that just wouldn’t stay meshed....but I was hoping I was wrong.

Now it’s a matter of finding a good used transmission in eastern N.C. because I doubt it’s cost effective on an 18 year old truck to go the rebuild route.

( when I had my shop I’d rebuild it myself but retired now at the beach )

 

Not allowed to do any work at the beach?

 

Shifter seat and bushing. Less than $25 parts. 1 hour install, if the old one isnt too gummed up like mine was. Ended up taking it to the dealer, still under $100 fix. Shifts like new, whereas before it popped out of 4th. These trucks rarely have trans problems, my money is on the bushings.

 

That's true, I had forgot how those lil plastic things can keep a shifter from seating all the way in place when worn.
Start with that. From Marlin I think for a better than stock one.

It's on top, under the boot. Easy to do at home.

 

Mine was bad at 65k...

 

Left my fully equipped shop and all the heavy equipment and retired to a 10x19 garage with mostly basic hand tools : (
P.S. I’ll look at the bushing but I fear the worst.....thanks y’all.

 

You'll know its the bushing when, well there is none. It should be little greasy bits of rubber that will have to be vaccumed out of the shift lever hole. I would be SUPER suprised if the bushing is fine at over 100k, like I said mine went at 65k. Go ahead and order up one of these: https://www.marlincrawler.com/transmission/shifter-parts/heavy-duty-seats
And these: https://www.marlincrawler.com/transmission/shifter-parts/heavy-duty-sockets

 

[QUOTE="cruxofthebisquit, post: 18491774, member:

I bet if you keep constant pressure on the shifter, it stays in gear?

[/QUOTE]

Even when I keep pressure on it it still just gently and quietly slips out of third gear only......I fear the worst but I will try the bushing first.

P.S.....I’ll update this but it might be a few days until I get to it

 

This is what the one from my 92 pickup looked like at 180k... Just a bunch of mushed up rubber bits.

 

/\ This is where I would start. /\

And BTW, the teeth on the gears are ALWAYS meshed in a modern fully synchronized manual transmission.
The gear is locked and unlocked to the shaft it rides on, the gear TEETH are always meshed.

 

I'm kind of old and worked on stuff that was old when I got hold of it so I'm sure poster above knows.
Just the fact tha you can't hold it in gear by hand makes me think the bits of plastic are keeping it from engaging all the way.
Always heard that was the better symptom to have.

 

Without getting too technical here, modern constant mesh fully synchronized manual transmissions generally have a main shaft that consists of an input and output shaft that are in-line but only locked together in one gear (usually 4th gear in a 5 speed gearbox) AND a counter shaft with a cluster gear. The teeth of the gears on the cluster gear are constantly meshed (engaged) with the teeth of the gears on the main shaft (hence the term constant mesh). However most of the gears on the main shaft are allowed to freely spin on the output shaft unless that particular gear is selected.
One of the ratios is actually just 1:1 and this is usually the top gear position in a 3 or 4 speed gearbox and 4th gear in a 5 speed overdrive gearbox. In that 1:1 ratio the input shaft is simply locked to the output shaft and none of the gears on the output shaft are locked to the shaft.

When a constant mesh manual transmission "pops" out of gear, it is usually the result a few basic problems. The simplest issue is a shifter that is not fully locking a particular gear to the output shaft. Because this is the simplest and cheapest problem to fix, it is where we first look.
Once issues with the shifter have been eliminated as the source of the problem, we move onto more expensive and serious potential problems.

Bad synchronizers generally show up with problems engaging a particular gear position but they can also show up as gears not fully locking to the shaft and "popping out of gear". Damaged splines on the output shaft and damaged splines on the individual gears can also show up in this manner.

The bad news is that after you eliminate the shifter as the source of the problem, everything else requires the transmission be removed and opened up. At that point you are looking at a transmission rebuild or a transmission replacement.

 

I got into it today......small bottom bushing is in perfect shape BUT the top bigger bushing is nothing but mush and small greasy pieces.

I need my little truck so I won’t be mail ordering ( but do appreciate the links to a better stronger bushing ) going locally now for a replacement.

I will report back on results.

 

Saw this thread and immediately thought bushing, but saw folks had already mentioned that. My '92 did the same thing except it was 1st gear, had about 110K on it at the time. The $12 bushing fixed it right up. I think you have to be really hard on a manual transmission to screw it up.

 

As I wait for my bushings to come in this evening , I’m recalling the last two manual transmissions I rebuilt .....a 1958 TriumphTR3 and a 1980 Ford Econoline. ( a long time ago ) No nylon bushings in them but then again they never shifted as sweet as this little Tacoma.

Live and never stop learning : )

 

Installed bushing kit this morning......That was the problem : )
It shifts like a new transmission and holds in all gears.

..................Thank you for all your replies.

 

Any resolve with this trans issue?

 

Yes......the bushing kit resolved all the issues. Smaller bushing showed no wear at all at 128,000 miles but larger bushing was gone, dissolved into a greasy mush.