Hey, this truck is really great but I am having trouble with the two speed rear end as it is reluctant to shift into high unless I play with the accelerator while rolling down the road. Do I have a vacuum leak somewhere or is it just stick because I only get about 6 miles a year on it?
Engine is flathead 239 V8, 4 speed non synchro tranny and has brake booster which seems to work fine. Your thoughts?

 

Howdy,


I would suggest having a look at the vacuum source, actuator and linkage. Put a vacuum gage on it and see if you have any leaks.

Then ensure that you have clean oil in the rear end. A lot of these old trucks have water in the rear differential and it has turned to sludge.

The "dogs" will not shift when you have torque on the rear end. That is, during acceleration or deceleration. The shifting occurs when you either let off on the gas during acceleration or push on the gas during deceleration



Regards,


Rick

 

This thread contains links to several other threads which have background info and info on the vacuum shift models.

As per the prior post, you can't just shift these like a transmission. Especially the downshift. The first thread linked to contains Eaton instruction videos on the two speed. A bit tedious, but if you are new to the two speed, watch 'em.

Beware, they are not kidding about NEVER downshifting the axle while going down hill.

https://www.ford-trucks.com/forums/1...peed-axle.html

 

YES!! Don't do it!!!!!