So I’ve been working on diagnosing this weird shifting pattern on my 1996 7.3 2wd, it’s got a triple disc converter, a sonnax accumulator kit with a .427” line mod valve, and a trans go kit in the valve body. When I first got the truck it shifted harsh, so harsh when it shifted into 3rd the whole truck jumped a few inches. I changed out the .500” line valve and the transgo springs to sonnax. I also bought a custom tune to improve the trans shift pattern. The truck no longer bucks when shifting but it shifts oddly. When I’m full throttle the truck shifts fine from 0-60 but when I am driving around town less than 25% throttle, the truck shifts as follows
0-15mph 1st gear
15-25mph 2nd unlocked
25-28mph 2nd locked
28-35 3rd unlocked
35-45 3rd locked.
when I shift into 3rd the truck is running at less than 1000rpm. It causes the truck to struggle to move and it shakes the truck a little. Is this a normal shift pattern? To me I’d say no, when I drive my ZF6 I drive around town around 1300-1500rpm not 900rpm. The VSS seems fine as the speed doesn’t jump, and is accurate. I replaced the MLPS and I do not have any trans codes. Other issues are, the torque converter locks hard sometimes. Sometimes a downshift to 2nd from 3rd is hard too. Any suggestions?

 

The ONLY reason the transmission shifts early is the tune. Nothing in the trans determines when it shifts or when it locks, it's all done by the tune.

As for the hard shifts that could be the aftermarket parts in the trans and/or the tune. Both the tune and the parts you replaced have an effect on how hard or soft it shifts. Everything seems to be out of balance here.

 

The tune is a less line pressure tune, I feel tempted to undo the transgo shift kit in the valve body and replaced it with stock or make sure it’s done right. My question with this is, when I take the valve body off, if the shift kit plate has holes larger than I’d like, all id need is a new plate and to drill the holes out to the correct size right?

 

Yes, that's right.

You can make a large hole smaller. Put a ball bearing on the hole and hit it with a hammer. You need to support the plate properly so you don't bend it. I have made large holes smaller like this.

 

So you’re just “flaring” the hole to a smaller size?

 

Yes. I flare it smaller than I need then drill it to the correct size.

 

Okay, that was on the accumulator plate correct? Is there anything with the valve body or it’s plate itself that can cause the rough shifts?

 

No, the valve body causes the shifts to happen, the accumulator body controls how soft or rough the shifts are.

 

So the rough shifting can be attributed to the accumulator body and it’s calibration plate?

 

It can be the accumulator body (including the calibration plate,) the tunes, or both.

 

Thanks Mark, just wanted to confirm what I needed to do before tearing it apart

 

Mark, since I replaced the transgo springs and valves with sonnax parts essentially making a sonnax accumulator body shift kit, should I remove the calibration plate? I notice all the other shift improvement kits do not use a accumulator body plate.

 

I guess I don't know what an accumulator body plate is. I thought you were referring to the separator plate. The trans won't work without a separator plate under the accumulator plate, there will be too much leakage.

 

It’s the plate in this picture

 

You need either that one of the original.