Engine dies when shifted in to 4 low reverse

[bronchole]

1997 Mountaineer, 5.0 v8, 4R70W trans, 4406 transfer case.

I posted this in the stock area because I don't think the problem is related to the modified portion of my rig.

It also momentarily dies when I am compression braking in 4low.

I noticed this the other week when I went on a mild 4wd trip (Rohwer flats). When I was going down some pretty steep hills in 1st gear low range my Monsterneer would momentarily lunge forward. After this happened a few times I noticed that the check engine light would flash in synchronization with the lunge and the tach would also drop to 0 RPM. The lunges would only last a fraction of a second, I would guess right at about 0.1 second. The only time I could get it to do this was when I was compression braking in 4 low.

Last night I was doing a bit of mild wheeling in the local hills and found that in 2wd if I gave it enough gas in reverse it would kill the motor. It didn’t take allot of gas, but something more than I would use in normal everyday driving. Well I needed to back up so I tried 4low. The motor would die as soon as I would put it in reverse in 4low. Pretty dam annoying considering I really couldn’t go forward. I needed reverse and I needed to do it with a little more gusto than the stalling situation would allow. I eventually coaxed it in to getting out by using 2low and some persistence on the gas. If I slowly brought up the gas to the point where it would momentarily stall the motor but held the gas at that position the motor would sometimes re-start and move me a little bit before it stalled again.

Last night when I backed it in to the driveway it didn’t stall, but I don’t normally use allot of gas to back it in to the driveway. I tried power-braking it in reverse and it stalled so at least I can reproduce the problem in my driveway.

So given what I have observed I am thinking that when the motor is torqued it a particular direction (I think lifting the driver’s side) that some wiring somewhere is shorting or opening which is causing the motor to stall. I will have to put a video camera on it to see, and measure the distances moved to stall in 2wd and 4low.

I have had the Monsterneer on 3 trips since replacing the 4406 I blew up. The first trip was to KOH and I don’t think I ever needed to give it any power in reverse on that trip. I have been driving it quite a bit to and from work, but never noticed this problem in everyday driving. I guess it is possible that some of the wiring running thru the area could have been damaged. I will look in to that.

I am mainly just looking to document this and see if there is some sort of common problem that I am not aware of.

I have searched using "motor stall reverse" and didn't see anything helpfull there.

Dan

 

[bronchole]

Well I found my problem. When the PO was doing a bit of work in the engine compartment he neglected to restrain the main wire harness to the bracket on the top back area of the intake. Over time the harness was rubbing on the edge of the bracket and wore thru the wrap and the insulation of a couple of the wires.

None of the wires had any major damage to the conductors, just the insulation wore and maybe less than 10% of the conductors on the smaller wires. One of the large conductors had it’s insulation wore thru, but no damage to the conductors. I wrapped each wire individually with electric tape. Then I zip-tied the harness back in to shape (I had to remove some of the factory tape to get in to the harness). I modified the bracket to reduce the potential of future damage and mounted the harness back to the tab.

I have done a bunch of testing and can’t get the problem to come back so I think this is it.

Dan