Hey everyone, new to the forums. I've been working on a '97 Powerstroke trying to get it to the point of being a reliable DD/medium duty tow rig.
I recently replaced the old auto tranny with a new remanned unit and have run into a couple odd issues I can't resolve. The tranny shifts nice and smooth until what feels like third gear, at which point it feels like either the TQ locks up or it goes straight to 4th and I go from being in the powerband down to about 1500 rpms lugging the engine fairly hard. Even when at WOT it stays bogged down and 9 times out of 10 will not upshift at all like it is supposed to. When cruising at hwy speeds at 60 or above, the TQ will consistently unlock after easing off the throttle, and with a mild increase in throttle it will lock up until I ease back off to the point of cruising at a steady speed. The ABS light triggers at 15 mph, not sure if that would have any affect on the tranny shifting funny though. I have no other engine codes. Also, the original tranny that came with the truck was on it's very last leg for duration it lasted but didn't issue the same problems, other than the TQ clutch being burned out completely.

Here's what I have so far done to try and fix this issue:
Checked AFT fluid and it's at the correct level
Checked all Trans harness connections
Replaced the VSS on the rear diff
Replaced the CPS

There is no tune on the engine, everything on the rig is close to stock form other than I have EGT and boost guages. I'm willing to look at anything and everything that anyone may think could be the issue. My next steps are to check TPS voltages as soon as I can find my meter and I will keep trying to notice any odd behavior and update this post with any findings. Any help is greatly appreciated as I have much to learn yet about the quirks of these diesels and their control systems.

 

Sounds like brake problems. Check to see if you have brake lights including the third brake light. Trans will unlock the TQ if it thinks the brakes are being applied. The ABS light is a red flag.

 

Find out what's causing the ABS light and fix it. That will affect the transmission.

 

Hot damn it was the third brake light, thanks a bunch fellas!

 

Your welcome, your cruise should work now also.

 

Yep, that's back online as well. Sure is nice to have that for the commute back and forth to work and college.

 

Similar problem but I checked my brake lights and all 3 work. It will not reverse in 2wd but it will in 4hi and lo. The TC disengages when I let off the throttle. Transmission level is good and it's a nice pink/red color with no burnt smell. I have an exhaust pressure code and computer code but the shop says that's normal when your truck has been programmed. My plan is to replace trans filter if there are no major aluminum pieces in the pan. I haven't replaced VSS but I'm not sure that could cause this. I'm new to diesel and transmission work so I seem to learn something new each month with this truck. Any help would be appreciated.
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Sounds transfercase - ish?

 

Turns out my #13 fuse to the anti lock brake,speed control,auto trans shift interlock,electronic engine control had been pulled out. 2 different shops told me $3000 for a new transmission. I overlooked it when I checked my fuses the first time. I just pushed in tight and everything works. There is a bit of a hard shift between first and second when I baby it though. When I get on it, it shifts perfect.