Hello everyone I’m hoping to find anyone who can assist in resolving my transmission problems.

Van is a 96 7.3 PSD E4OD (2wd pan) that has been converted to 4x4 with a BW1356 Tcase. The motor is stock, the Exhaust back pressure valve was deleted and the turbo has a wicked wheel inducer.. otherwise stock.

a few months ago my vans torque converter died on me in the middle of the road.. had it towed and had the transmission completely rebuilt, new billet TC.. picked it up and drove it.. for a few blocks and noticed a bogging when coming to a stop.. like the TC was locking up at idle/ stop.

Brought the van back to the trans shop.. they changed out the solenoid pack.. new fluid.. worked for a day and started bogging..

brought it back and they pulled it apart again, new billet TC.. problem persists.. they are saying it’s an electrical issue & recommended a shop that has a 2 month backlog. I’ve since rebuilt the trans harness.. and tested the trans by unplugging the harness after starting the truck.. still has the issue so it’s isolated to the transmission itself I believe..

it gets worse.. now when I start the van and place it into reverse it stalls the motor, if I place it into 1st it will stall out. Sometimes even going into drive.. stalls the motor.

Things I’ve checked.

1. Fluid levels seems high on the stick, I plan on using an extractor to pull some out and retest..
2. The wiring harness to the transmission solenoid pack and NSS was removed and completely rebuilt.. probe tested continuity at all circuits, no issues.
3. I’ve started the van & unplugged the trans harness and it still stalls out when shifting into reverse or 1st. (assuming this rules out electrical causation)
4. Idle validation switch, brake switch, TPS@ pedal all good.
5. someone recommended I check the check valve on the rear passenger side of the trans.. pulled that out.. no issues/ blockage.


only other things that could cause this from my research..
1. Internal leak
2. feed bolts loose
3. something/ debris stuck in the solenoid/ valve body
4. too much ATF causing cavitation and air to enter the system causing lockup?
5. To little ATF? (Unlikely)
6. Wrong filter installed? Can you even install the 4x4 filter in the 2x pan?
5. Trans filter has come loose?


any suggestions insight/ wisdom appreciated! I’m not a transmission expert but I can wrench fairly well.

 

Check the purple/? wire that's your TC lock up wire might be grounding.

Did the shop also replaced the radiator and trans cooler when they rebuild the trans? flushing them never really works specially if the trans/TC greanaded.

 

It can't possibly be that. He said it does it with the wiring harness disconnected. That eliminates the wiring and everything electrical as being a possible cause.

That's a good point. If the cooler and radiator were not replaced it is likely that debris from the old trans has found its way into the new trans, causing issues.

If the fluid level is right, the problem could be a leaky seal on the input shaft, a sticking torque converter clutch control valve in the pump body, or other internal leakage. A 4x4 filter won't fit in a 4x2 pan, it's too tall. A problem with the filter could cause this.

 

Thanks guys. Yes we tested the TC wire continuity along with all of the others by unplugging the harness and testing continuity from the battery - and + to all the harness wires, no issues there. Started the van and unplugged the entire harness and the problem continued.

I reached out to transgo and they said it’s a common issue they see often.. he wanted the trans shop to run pressure readouts in all the gears at certain rpm’s. He said 99% sure it’s a line pressure issue.

I was able to lug the big *** van down to the trans shop and explained the horse**** I’ve gone through trying to figure this out..

this is the 2nd trans and billet TC they built for this van…. and both had the same issue.. I told them it’s something related to the new TC’s, the coolent loop, or internal causing line pressure issues.. NOT electrical..

I told them to get the pressures logged and run a bypass or bypass the stupid OEM trans cooler to test it.. van is a 96, it’s a small little joke of a cooler mounted on the motor cross member..I’ll buy whatever 6.0 trans cooler whatever just get the ******* from stalling!

 

this is an older van so it does not have the newer style water/ oil cooler style, just a small little trans cooler on the motor crossmember.. they did flush it.. do those machines test flow? Who knows.. Had I known it should have been replaced or upgraded I would have done it no question, but that was never a discussion/ suggestion with the trans shop.. I’ll keep you posted if they ever figure it out. I hope it’s something silly like a plugged cooler but I guess we will see.. this started in October..

 

When it left the factory it had a transmission cooler in the radiator. Some also had the small aux cooler out front.

 

ok, would this be something that can be solved with a Hayden cooler while I try to source a new radiator? Trying to minimize down time at this point. I know you are a fan of the efficiency of the radiator coolers and I get it.. just trying to get this on the road.

 

Now they are saying it’s the map sensor.. I found the only one in sandiego and went down there and installed it in 2 mins..

they said trans pressures at idle were
at park 140psi
drive 140psi
reverse 200psi

hey didn’t give me WOT values since they are convinced it was the stupid MAP sensor.. I told them if it’s running a code/ suspect just unplug it.. that didn’t compute to them..

 

Yes, you can do that.

 

Hey mark, would what appears to be notably high line pressures cause this issue? We are getting 140 psi at idle.. should be around 95.. trans shop said that didn’t seem right.. pressure regulator valve/ pump maybe? They will bypass the cooling system next.. the saga continues..

 

using Mercon V or Mercon LV?

Mercon LV is very thin and can pass though seals activating the TC lockup

 

Yes, high line pressure can cause this. It could be the EPC (Electronic Pressure Control) solenoid or the regulator valve, or something electronic. What is the commanded pressure, which can be read with Forscan?

 

it’s down at the trans shop right now so I can’t really check.. they have a snapon scanner, what should that reading baseline be? They were still hung up with the stupid map sensor.. I told them to just unplug it if they think it’s so detrimental.. told them those pressures are pretty high above normal and they seemed to agree..

 

 

thanks! The TC started making a “noise” when they were trying to figure out the issue.. they called me today saying they are pulling the trans again (3rd time) I told them they really should check everything related to pressure regulation since those line pressures were like double what they should be in your chart! Also told them to check my flex plate for damage.. all this stalling can’t be good for it..