I just put synchros in this trans and it still does the same thing. Put it inreverse let out on the clutch it pops out and grinds. Repeat a few times and it stays in. I was going to drive it for a while to see if it would get better but I need to pull it again because it is leaking from the front seal. Anything else I can look at while I've got it apart like shift forks?

 

Hoping out of gear is a sign of worn bearings. You had the trans completely apart and didn't put in bearings?!?!?!

 

Yes I did bearings and synchros.

 

Did you look at the shift collar? Mine were all pretty worn.





Did you set the main shaft bearing and countershaft bearing pre-load when you replaced the bearings?

 

I did not check the preload. There was no end play.

 

I rebuilt the ZF in my truck due to the same issue. The reverse gear and thrust surface on the mainshaft were very worn, allowing the reverse gear to move far enough from the slider to keep the slider from completely engaging the reverse gear. Fixing this issue required a new mainshaft and reverse gear. However, I think you would have noticed this when replacing synchros if it was your problem. I wouldn't worry too much about the pre-load...bearings are manufactured with pretty tight tolerances - much tighter than the pre-load spec range. Now if you replace the mainshaft, that's another story.

 

Mine pops out also, I haven't really checked it out, but I figure it's either the clutch or maybe the firewall flex. I don't have a problem with any forward gears though. for reverse I pump the clutch 3 times and it drops right in if I'm sitting still, If I'm slightly rolling forward, I can push it into revers without pumping the clutch.

 

Its not about the bearings or how they are manufactured. They are tapered roller with a separate outer race. If you don't have the proper preload as the transmission heats up the case (aluminum) expands at a greater rate than the main/countershaft (steel), the bearings can become loose in the outer races. That's not good.


Same concept of Ford specifying a torque spec on the front wheel bearings. You wouldn't install the castle nut by hand on those with no torque spec, would you?

 

In about 25 years working as a professional auto mechanic, I never used a torque wrench on a wheel bearing, or ever saw anybody use one.

 

kawamatt2, my comment wasn't intended to imply disregard of the preload entirely. The point I was trying to make was if you put new bearings in the same case with the same input shaft, mainshaft, and countershaft, the bearings and races are so close in size to the ones that were replaced, the preload should be pretty much where it was when the transmission left the factory. I understand the need to set preload properly given the aluminum case, steel shafts, and differences in coefficients of thermal expansion and agree that the proper preload is essential for proper operation. If any parts are replaced other than bearings and races (input shaft, mainshaft, countershaft, or case halves), I agree that pre-load should be reset to proper specification by re-shimming the front bearing races.