Cabover shift linkage slop, what to do

[rectifier]

I have an old 1972 Ford C700 3-ton grain truck that has always had the same issue. When you put the stick forward, it hits the dash. When you pull back, it hits the seat.

It barely makes it into gear and sometimes you have to take several swings at it. On top of it all, it's sometimes hard to decide what gear you've shifted into and it can be a nasty surprise! So I never shift on a hill these days, I pick a gear that I know will make it and chug up the hill. It's frustrating and makes hauling grain a not-fun experience. I would sure like to fix it this year.

This is probably not quite the right place to post this, but I wonder if anyone else has a cabover where they've had to take slop out of the linkage. The linkage transmits the shift information by sliding back and forth and rotating. As I see it, where the shaft slides in the bushings there shouldn't be any slop, as the bushings only support the shaft, and the shaft has not grown or shrunk lengthwise. However the rotation passes through at least 3 U-joints which could have gotten tired? Or it could be in the shift forks and not the linkage at all?

 

[Oldtractorfixer]

Ours has similar problems. The problem on ours is located at the front of the shifter shaft system that goes back to the transmission. There is a lever on a shaft there and it is loose on the shaft. To find your problem get under and have a helper try to shift. You will see some where that is not connected securely.

 

[fidowanttobe]

Ours has similar problems. The problem on ours is located at the front of the shifter shaft system that goes back to the transmission. There is a lever on a shaft there and it is loose on the shaft. To find your problem get under and have a helper try to shift. You will see some where that is not connected securely.

Yup. Two guy process. Usually can take a lot of the slop out of shift linkages due to wear by trial and error with the adjustments. The forks probably do have wear on a 45 year old truck but my money is on the linkage.

 

[Looking4new]

Maybe you can shorten the linkage? If the external shift linkage has threads on it? Or does the shifter go straight into the tranny?ie when you jack up the cab the shifter stays put and the cab goes up anyway. The reason I ask is my 1988 COE Freightliner the linkage would telescope and still stay connected to the tranny, but the shift lever would go up with the cab.

 

[Stimw]

Is this a truck that has linkage to the transmission rather than a stick out of the top of the transmission?
Also So that you can tilt the cab.
You might look at this link, you are not the only one- Google

 

[rectifier]

We went out to have a look at it today. There are about as many sources of slop as there are parts in the linkage. By the time you get to the transmission you can rock the stick about 6" either way with no movement of the forks. Some joints are in good shape but had poor tolerances from the factory, which doesn't help the issue!

There is nothing to adjust except for the length of the linkage. When I bought the truck I adjusted the length to get it home, but further either way and it bashes either dash or seat. Hopeless.

Main issue is a worn bushing on the right end of the support tube that runs across the front. Has a grease nipple but was likely rarely greased. This allows one of the joints to wallow instead of operating properly. Of course everything is together with pins and there's hardly any room to swing the hammer. I'll try to drop that tube assembly and see if the bushing can be extracted.

If I get the bushing replaced I'll likely go through and shim up a lot of those sloppy joints from the factory as I know at least 3" of that slop comes from excessive tolerances.

 

[DJ54]

On the old C-8000 I had for a snow plow truck, there was a greasable eye the shaft running back to the tranny went through. With all of the salt & slush, that needed to be greased quite often, or it would start binding, and make it hard to shift.

Was off on vacation one time, so they put another driver in it. When I came back off vacation, I found the shifter to be in this condition. Got the mechanic, and we found the problem. The other driver had rammed & jammed so much, it spread that fork. Had to heat it, to bend it back. After that fix, it worked like new, after a good greasing of the eye & linkages. It had a 13 spd. in it, so there was LOTS of shifting..!!