92 3.0 5sp trans locked up?

[Rick W]

Hi, I’m still looking for a 2.9 V6 for my 87, but in calling around, a contact just called me back with this.:
He has a short cab, short bed, 2wd 1992, manufactured in 8/91, that has the 3.0Lv6, and a 5-speed Manual transmission. Trans code M; axle code 84.

truck was running great, and as he pulled into a gas station at a very low speed, the rear wheels locked up, a little “screech.“ He thinks the clutch is OK, but he cannot shift it in or out of any other gear, and the back wheels are still locked, he had to be towed.

here’s my question: I’m looking for opinions on whether the rear end went bad or the transmission went bad. There were no whines or roars or growels or grinding before it locked up.
Hence I assume it’s something in the transmission, but if it was running OK before it locked, is it necessarily a bad transmission or is it something more simple inside the trans that would cause it to lock up? I don’t know a lot about these, So if anyone has any other ideas, I would appreciate some advice on what the problems might be and what it might cost to fix.

 

[Rick W]

Btw, only 102,000 miles, adult driven

 

[RonD]

I wouldn't think rear end, that wouldn't effect or prevent transmission from shifting into any gear or neutral

Best bet would be a shift rail roll pin sheared off, so transmission is in TWO gears at the same time which locks the output shaft, i.e. locks drive shaft and rear wheels

Pull out the shifter, like you are changing the bushings and have a look down inside
There are 3 shift rods
1-2
3-4
5-R

Each rod has a slot for the shifter arm
All slots lined up in the center is Neutral

The way its set up is that when you shift in to any gear the shifter arm is now trapped in the gear, so you have to move it(shift rod) back to center/neutral to move it to another shift rod and gear set, this prevents you from engaging 2 gears at one time

These shift rods have the shift forks that slide the gears to mesh, a roll pin holds the shift forks to the shift rod
If the roll pin shears of, i.e. trying to FORCE trans into a gear, then shift fork can move on its own, so you can get LOCKED into 2 gears

Anyway look down the shifter hole and see if slots can be lined up in the center, use a screw driver


OR.................the transmission could have just broke, lol

 

[Rick W]

Great advice, we’ll take a peek.

if it is as you say, can it be fixed without removing the trans?

 

[RonD]

If you are willing to pull the seats and cut the floor plate, you can pull the top cover to service shift rails

But dropping the transmission would be best

You have an M5OD-R1(M5R1) loads of picture out there and videos

Its the same as the M5OD-R2(M5R2) just smaller version so looking at either will help

 

[Rick W]

& I’m hearing between the lines that if I get it free and lined up, it could lock up at any moment again, y/n?

Would the shift handle also be stuck/locked, or will it flip around?

Hence, i’m assuming that if I can pull it with Big Red like when I got my 87 4wd (see pics), I should pull the drive shaft to tow? Any tricks to that, pulling shaft?

 

[RonD]

Yes, pull drive shaft, unbolt it at rear axle, 4 bolts, assuming 2WD, and it should just pull out of transmission end

If two gears are locked, shifter may stick, it would depend on what happened inside

 

[TurboRay]

.
Have you determined for sure that it's the trans - and not the diff - that's causing the prob? Since the dr/shaft has to be removed or at least disconnected to fix either.....I suggest disconnecting it, as RonD recommended ~ which requires a 12-point 12mm socket or box wrench. Obviously, if the truck isn't on a hoist or jack stands, make sure the E-brake is applied if parked on an incline.

After disconnection, you'll then be able to determine what's locked. I suspect that it's gonna be the trans, as most have prophesied, but it's good to find out for sure before fretting over potential costs and repair strategies. .

 

[Rick W]

Update, when we fiddled with it, it turned out the engine locked up. There’s a lot of slop in the shift lever, which I’m pretty sure is the shift lever bushings in the cab floor. It rolls fine in neutral or with the clutch in.

the guy is in East Atlanta and he’s getting $225 to scrap the whole truck. I think he has to move it by Monday night. I’m sure he’ll take $3-400 in a heartbeat. It’s a straight truck, no bad dents or rust, except a weird spot high on the bed on one side halfway back. Short cab, long bed, very good high-back red seats. It’s dirty and worn, nothing of value under the hood, but the body, interior, frame, etc. seem fine.
If anyone is interested, contact me off line & I’ll connect you, it I think it has to be moved quick.

I probably know a wrecker guy who’ll pull it and store it a few days for $150-200.

it was running & has a current tag.