I have a 2000 f350 with a 7.3l and a 4r100. I just rebuilt the transmission. Now after when you get on it to pass when you are in 4th gear with the converter locked, when it downshifts it slams hard into 3rd gear. All other shifts feel great up and down. Wondering if anyone has had this problem before? And any fixes?

 

Any modifications done during the rebuild, shift kit or anything like that? I'm by no means even what I'd consider knowledgeable about transmissions let alone an expert, but I believe shift characteristics are determined by fluid pressure which is metered via hocus pocus in the valve body. So a guess would be whichever spring or ball that's supposed to vent excess pressure isn't installed properly or was swapped with one of the other ***** or springs by mistake. Other than a bump that's about all I got.

 

It was rebuilt before about 90,000 miles ago. Not sure what was done to it then but I didn't put any shift kits in it.

 

How many of those 90k did you put on it? How much history do you have on the truck?

 

There is a 4-3 shift valve I believe. Can’t remember it’s name. Looked through some notes on my phone shortly after you started this thread but didn’t find what I was after.

When I bought my truck the transmission had been rebuilt. The shift from 4-3 would make me cringe every time. Possibly unrelated but the TC ended up going out on it. So I did my own trans rebuild.

The previous rebuilder had used a Transgo Tugger kit. While going through the Valve Body I found the 4-3 valve was in backwards (spring was also cut down). I spoke to Transgo about this wondering if it was part of the shift kit install. When I told him a valve was backwards he laughed and said “let me guess the 4-3” (again I can’t remember the actual name). He said this was an old trick people used to do to firm up the shifts and it was silly. I replaced the spring and put the valve in correctly. Wow what a difference!

All that to say, I don’t know what your issue is but I would be looking into the 4-3 valve. Maybe you accidentally put it in backwards? Maybe it’s sticking?

If I get some time I’ll pull out my old laptop that had the information on it. Until then I’d recommend googling the 4-3 valve.

 

Mine is actually doing this with 5 out of my 6 tunes from Jelibuilt. It's annoying. My trans is stock. I am hoping they can fix it. In the meantime I leave it on modified stock and it shifts normally.