Archived What would cause a very harsh 3-4 shift?

[Allnew2Me]

I rebuilt my transmission a couple months ago but the valve body was not manually shifting into second gear so today I installed a replacement valve body, new in the box. My second gear issue is solved but now the transmission has a very, I mean really hard 3-4 shift to the point that I don't want to drive it. I noticed that when accelerating it does the bang shift but if I am in OD and decel, and turn off OD it will go to third and when I turn OD back on it shifts normally back into OD. I'm thinking that maybe it is shifting 3-4 with the TC locked.

What would cause this and can it be fixed without having to pull the valve body again? My manual says a harsh shift can be a faulty lockup solenoid, does that make sense? Thanks for any info.

 

[Missouri Mule]

My book states the same thing.

You could try a band adjustment.

 

[zstroken]

Band admustment has nothing to do with 3-4 shift. You could be shifting locked. You could find the TC lock wire and open it, or whatever so it can't lock and then try it.

 

[Allnew2Me]

Thanks for the thoughts. I am not going to drive it until I can talk to Suncoast or my trans guy. I think it is shifting locked and I don't know why that would be with a brand new VB, nothing else changed.

 

[zstroken]

Wiring problem on the truck. If a wire has rubbed through allowing the wire to touch ground, then the solenoid would be on all of the time. With a stock 47Re VB you would not notice it because hydraulically you can only lock the solenoid in 3rd and OD.

 

[Graphic man]

3rd to OD will shift locked to locked... . the 47re do that, but it sounds like you may have something going on in the V/B

 

[Jim Fulmer]

3rd to OD will shift locked to locked... . the 47re do that, but it sounds like you may have something going on in the V/B

Depends on the software, mine won't but yours will as Dodge made that change after my year model to try and take care of the sloppy converter... ... . I want to say 01' they did the change.



Jim

 

[Graphic man]

Depends on the software, mine won't but yours will as Dodge made that change after my year model to try and take care of the sloppy converter... ... . I want to say 01' they did the change.



Jim

your right Jim..... i though it was 98. 5 or 99 they started it..... but i may be wrong.

 

[Allnew2Me]

Well I spoke with Suncoast today and it is shifting locked. It is "normal" for this to occur with this valve body, the problem is that with the increased line pressure it creates a very harsh shift. It is a communication problem with the PCM telling the valve body to lock in third and then shift to fourth. I am sending it to them for an adjustment. Thanks for all the input.

 

[flattracker]

My 01 did the same thing with the DTT valve body.

On the top of the valve body is a small cover with a hole in it that covers the boost valve , the aftermarket valvebody companies drill this hole out to increase boost pressure on tc lockup and 3-4 shift.

On the o1 and 02 the pcm will allow locked 3-4 shift at part throttle causing a very harsh shift with with the increased boost.

Mine was drilled out to . 150 from Dtt, I replaced it with another that I drilled to . 095 made for much more civilized shifts.

If you are running big hp you will have to live with the harsh shift due to needing the increased lockup pressure.

 

[Allnew2Me]

Flat thanks for the info. I am not running high HP and don't want to live with such a teeth jarring shift so I sent the VB back for what probably is the modification you are talking about. The funny thing is I have the 48RE VB that was having a manual 3-2 shift issue, and this VB was supposed to correct that which it did, but it has the hard shift where the other one did not. I was told that the second one was a newer version.

What I did was send the first one back that shifted fine 3-4 and they are going to correct the non-manual 3-2 shift issue for me. I'm hoping that will do it and I can just drive the thing now.