Hello-

I have a 1972 Blazer 4 wheel drive with an '08 L92/6l80 combo from a H2 Hummer with 13k on the clock. I am running an NP241 transfer case from a 1989 GM into 5.13 geared 1 ton axles.

The engine all stock except for Doug Thorley headers and a fabbed intake duct (not manifold) with AFE filter. I had the ECM and TCM tuned to match the truck/running gear. I changed the trans filter and put new Dexron 6 synthetic in. The trans cooler lines run up the driver's side block and into an aluminum radiator. So far, the engine temps have not passed 225 degrees

I currently have ~600 miles of driving almost all short trips as I try to work the bugs out and get used to the truck. Enter my problem: When driving, the transmission feels like it is 'binding' up. I have to give it more and more fuel just to keep a steady speed on flat ground. It has happened three times so far. When I pulled over to check things out, I didn't need to brake to a stop. When I tried to go, forward or reverse, it felt like the parking brake was on (it wasn't). I shut off the truck, unplugged the connector at the back of the transmission and plugged it back in. Started and drove just fine. I did have my TCC brake wire incorrect (+12v when brake not applied as per PSI instructions) now it is 12v with brake applied and the binding has occurred with both wiring arrangements.

When the 'binding' occurs, it starts to gradually need more fuel to go the same speed on flat ground. When I pull over, and stop and try to go again, it feels like you have one foot on the brake, and one on the gas at the same time and if you give more gas it will move begrudgingly. No grinding, no popping, no noise or fluid puking out anywhere and no CEL.

What makes me wonder if it is in the tune, is the fact that I can disconnect the electrical to the transmission for a split second, fire up the truck and drive like there was never an issue. Almost like it turned off whatever was at fault. I think it would still be binding if it was a mechanical issue.

Thanks for the help!

 

Weird problem. Given the plug issue, this can't be it, but are u sure the brakes aren't sticking? On my swap with same motor and trans I also reconfigured my brake pedal and realized the pedal was applying the brakes just a bit. As things heated up the brakes would get to the point of almost locking.
I had to readjust the pushrod between the brake pedal and master cylinder.

Initially, I did have an internal trans problem that caused my trans to act like I had a trans brake on. Symptoms sound similar, but this would have the drivetrain throwing codes and going in to limp home mode. This required up stacking the transmission. There was contact at one of the clutch baskets and chalked up to assembly error.

What are the trans temps? I'd expect if you were locking up internally, you'd have a heck of a lot of heat to dissipate. I haven't seen over 175 at my trans cooler in my swap at the pan or cooler. I'd check that.

Check your brake rotor temps just for giggles.

I use an IR gun to measure temps. Cheap at harbor freight and real easy to use.

Any pictures of the MAF plumbing? What size tubing did you use? I noticed 4" was too large and 3.5" too small.