Question 2001 Excursion transmission no forward gear

[Chewman]

I have a 2001 Excursion with 24K on the rebuilt transmission. The trani shop that rebuilt it has gone out of business due to health issues.

History, I have manual lock outs due to vacuum leak in the system for the auto-hubs. If I run in 4x4 for long periods of time the heat goes to mix defrost and heat. This happens faster in low range.

Recently I was moving a trailer and had it in low range for maneuverability. I got the trailer where I wanted it, unhooked, went ot move the excursion and no forward gears. I let it set for a couple hours while I quit cursing. I came back, fired it up, still no forward, drops into reverse like normal. Back to drive, nothing, R- drops in normal, Drive =nothing, R-normal, Drive it dropped in and moved forward. I drove it around the block and it seemed normal. Back in the drive it went from R to D multiple times normal. Drove it for a few 100 miles no issues. Pulled my 24 foot enclosed trailer, no issues.

This weekend moving a trailer I again put it in low range and again lost forward gears.

Thinking about the vacuum leak I shut it off, cycled the key to forward to let the vacuum pump run, after a few minute fired it up and it dropped right into forward - drive without issues.

What do I have going on with the transmission? IS it the vacuum leak like I suspect or is it a bigger issue?

Thanks for the help and education!

Chewman

 

[snicklas]

I would first plug the vacuum lines to the front hubs since you no longer have the vacuum pulse hubs. The HVAC going to defrost is an indication of a vacuum leak. I would trace the lines back as close to the vacuum pump on the passenger inner fender and plug the line.

Not sure if the vacuum leak is causing a shifting issue in the transfer case. The shifting should be 100% electric with the shift motor. But, the system being monitored by the "computer" it may be a failsafe if the hubs do not shift because of a vacuum leak, the computer may not allow the transfer case to shift. I still have the vacuum pulse (ESOF) lockouts and have replaced all the seals and the like, so I have not run into this issue. I would fix the known vacuum leak first, then troubleshoot from there is needed.