bman22

I've got an '01 LM7 and 4L60E swap in my '87 Blazer, something I did this past January. I did all the wiring harness and electrical stuff myself, sent the computer off to somebody on eBay for the tuning.


It has been driving fine now since then, regularly being used, and even just yesterday I had it out wheeling. This morning when I was headed out for another meet, I made it a block down the street and then the transmission went into neutral. The reason I think this is a computer issue and not a physical transmission issue is that the gear indicator (I've got a matching '01 Silverado gauge cluster in the truck as well) has stopped working. Typically, without the P/N wire on the cluster wired, it just shows no gear when in either position.

Now, no matter what gear I've selected on the shifter, the gear indicator reads as if the transmission is in Park/Neutral, and an OBDII scan says the same.

I tested the Park/Neutral switch to verify that the range sensor was working, and it produced the exact signals the chart I found online said should be produced on the 4 signal wires.


I'm at a complete loss as for what might be the issue?

kevin87turbot

iTrader: (2)

Disconnect the main harness connect from the transmission. That will force it into limp mode which maxes out line pressure and allows manual 2nd gear and third gear and reverse. If it passes this test, then you know that the Trans hard parts are good.

bman22

Well, I pulled the plug, the gear indicator started working, but unfortunately the transmission still wouldn't put power to the wheels in any gear. So that suggests the trans is broken then, I assume? It makes no noises at all, just like it's in neutral.

Any idea why unplugging the main harness on the transmission made the gear indicator start working again?

kevin87turbot

iTrader: (2)

It is certainly a problem in the trans. Try this...check the fluid level with the engine off, then start the truck and check it again. The fluid should drop Well over an inch on the dipstick when the truck is running. If it doesn't drop, the the trans pump is broken or the converter hub is broken.

bman22

Will do. I can't believe it let go while barely on the throttle instead of while hammering on it while in first hold yesterday.

Is it possible that this is a result of low fluid? I know I should have checked this first, but my driveway is really steep and I know you should check it on flat ground. It leaks a bit, but I checked it not that long ago, so I think it should be ok.

bman22

Fluid level doesn't change running or not. Guess I'm dropping the transmission...


Had to happen sooner or later, I definitely drive like an *******.


I guess I'll head over to the transmission section and see what they suggest as far as rebuild work.