I have a ‘93 that is used for towing a gooseneck stock. It has been hard shifting intermittently. Hardest shift is between 1-2nd and feels like a clunk. More recently (the past 2 weeks) it has started to race and then shift very hard between 3-4 on occasion, causing the whole truck to lurch. If I let off the gas and do a few light taps when it starts to raise this seems to help it and I can avoid a severe lurch,

Problem started as just a very subtle hard shift in March after I had the fluids in the truck looked at/replaced as needed. Originally we thought it was air infiltration. The mechanic looked back over everything they touched and didn’t find a problem.

In April, took to a mechanic who found a short in the rear differential ABS. Replaced this with a used Ford part.

All the problems went away for a few months. Now, they are back and much more severe (as described in beginning).

No error codes.
Truck has 46K miles.

It used to shift like a dream so this problem is incredibly frustrating and I worry about long term transmission damage.

I need it to move horses in a few days, and am torn on if I should get it back to a mechanic right away and risk making the problem worse before the trip. When they checked the differential ABS the first time, it caused lurching through the entire vehicle and killed my speedometer. I don’t like driving it while it is hard shifting in general let alone towing 8K behind.

Thoughts on what might be up and how to proceed? Is it worth checking the ABS differential even though the problem might be worse?

I don’t have a trusted mechanic yet as I am new to the area, so hoping for some guidance on the best ways forward. Thank you!

 

You are right , driving it with the engine racing is not good for anything.

If your mechanic has checked the throttle linkage for sticking /binding, something like "stuff stuck under the accelerator pedal often gets overlooked.
If none of that applies here, you might ask them to check for a vacuum leak under the carburetor mounting. Not an easy one to just tumble across..
Have had a few of them with the vacuum leak there and engine racing, worth looking into. Simple replacement of the gasket got rid of the racing problem

 

The racing is intermittent and rare. It is when it goes to shift—like it does not know what speed it should be activating the shifting at. This is a recent development that is paired with the hard shifting. Normally engine rpm is fine and it is ok again after shift.

I’ll have them check for the vacuum leak in the carburetor just in case. I’ll verify about the throttle linkage as well.