Stuck manual transmission?

#1

Help!

I have a problem with my truck:

I own a 1994 Ford F250 4X4 with a 5 speed manual transmission (ZF S5-42) and a 5.8L gasoline engine. I bought it used several years ago and it has been a good truck.

I am in the military. I was ordered to move, so I packed everything up (Put the truck on a dolly behind the U-haul) with the front wheels on the dolly, rear wheels on the ground. The transmission was in neutral, but I did not disconnect the driveshaft.)

When I arrived at my destination I had the following problems:

The truck is ?stuck? in third or fourth gear. When I depress the clutch, the transmission disconnects like normal. With the clutch depressed, when I move the stick shift from gear to gear, it seems to move, sound, and feel normal (normal force, normal range of motion, normal ?clicks? from the detents) however, no matter what position the stick is in, the truck never leaves the third or fourth gear it is ?stuck? in. When I release the clutch, the transmission engages in the same gear- even if the stick is in neutral. The Transfer case works as normal; neutral allows the truck to idle with the clutch not depressed, and the truck can drive in 2H, 4H, or 4L.

I removed the transmission and inspected the clutch. The pressure plate, clutch disk, and flywheel all show a lot of wear; but are intact and seem to function normally. The release bearing is pretty dry.

I opened the case on the transmission. Everything seems normal. All of the shift rails, forks, and detents look normal. There are no broken parts, or metal chunks inside. The synchronizers all look O.K to me (I have never seen the inside of a manual transmission before, but it looks clean and solid.)

I really need to fix my truck. Can you help me figure this out?

Thanks,

Wayne Hyman

#2

Since you have it opened up, did you look for movement inside the trans when you “shift” it? What are the forks doing?

#3

I am unable to move the rails much, more of a wiggle. The forks seem to be trying to lift the synchronizer clusters, but they are not moving much (I assumed this is because the engine is not spinning or that I am not strong enough, the stick on this thing is about 2.5 feet long, so there is a lot of mechanical advantage.)
Also I believe that the transmission selector is still in neutral, but when I turn the input shaft, the output shaft turns as well.

#4

How far did you tow it? I’d suspect a lack-of-lubrication problem. Gears and bearings that get lubed in normal operation get “starved” when only the output shaft is turning. That’s why the manufacturer recommends driveshaft removal for “rear-wheels-down” towing, even with a manual transmission (over a certain distance).
You’re ahead of the game, though, since you have it already out. I’d seek out a well-recommended trans shop if I was you, and have them take a peek at it.

#5

Sounds like the input/output pilot has seized.

Was the truck carried very high at the front?

#6

The truck was on a U-haul dolly, so the bottom of the tires were about 12" or so high. What is the input/output pilot?

#7

Internal shifting linkage. With stick in neutral, remove stick. The points on all the rails must be in neutral. Look for the odd one and move it. Hey, you’re stuck right. You can experiment. Something crazy happened. One of the other ends of the shift rails may have broken, so if one moves really easy, you may have found the problem. It’s easier to see with the tail housing removed if the shifter is practically on top of it. If there is no gasket, you will have to reseal it with RTV sealer or it will leak the gear oil slowly. I have never worked on your model transmission or truck so I hope I’m not hurting anything.

#8

I will second the idea of a damaged and possibly fused input gear to output shaft pilot bearing. This bearing is a free roller bearing between the nose of the main/output shaft and the rear of the input gear/clutch shaft. How far and fast did you tow?

With the transmission in neutral while being towed, none of the gears were turning so no transmission oil is being slung inside the transmission. The main/output shaft and rear bearing are turning. The output shaft is spinning inside the stationary gears. So the bearings that were without lube were the input/output shaft pilot bearing, all the bearings inside the individual main shaft gears, and the rear main shaft bearing.

If you have the transmission out, unbolt the input shaft cover and attempt to pull the input gear out of the transmission. This is going to be difficult if the pilot bearing is fused. If you can get it out you can assess the damage.

Get back to us with your progress, assessment, and questions.