90 f-250 4x4 trans pops out of reverse????

[jigfeett]

Hey all, just got a call maybe some of you may have seen this. 1990 f-250 4x4 5 speed manual trans, it pops out and makes a grinding sound but will go into gear and work fine sometimes just by putting in nuetral and trying reverse again. Other times it has to be put in 1st gear and then to reverse and away you go. Now the things I checked so far are the shifter and the end of it shows no abnormal wear and tear. I looked down as far as I could and did not see any damage on the shift rails or mechanism but suspect the problem is in that area.
What do you think?
thanks

[Transman]

Have you tried putting the transfer case into a different range? I have seen the forks wear out and cause erratic problems with the trans. If no change then inside the trans itself. How much of the shifter have you pulled out, just the stick or the whole shifter housing? Which trans model is it (big aluminum guy with big ZF on it) or the top loading? If it's the "M5OD" then reverse gear is inside the tailshaft, the output shaft nut tends to walk out causing your symptom and fairly easy to repair in the vehicle except when it's 4X4 because you have to remove the transfer case to get at it. Post back, Transman

[jigfeett]

thanks, it is 4X4, I will find out which model it is. I pulled out the stick and checked the ball on the end and looked inside as far as possible.

[jigfeett]

  still working on it, it is the   ZF big Aluminum  5 speed or 4 + od......when it pops out is makes a grinding sound and I've found that if I put it in 1st gear and pop clutch for a half second then it goes right into reverse---
Any more thoughts??

[jigfeett]

any hints on this??it is the big zf type---if I lurch it forward it usually goes right into reverse.....any help....
thanks

[Transman]

Although you haven't said if it makes any other noises besides when it pops out of reverse. I will "assume" that it does. These units are, at best, difficult to repair. I know of very few people in my town that would even think of trying to fix them, besides myself. They have several common problems including syncros & bearing problems. They are fussy, sensitive to exact tolerances AND require some expensive special tools. My recommendation for you, unless you are already experienced with these units, would be to purchase a complete unit from Jasper or Rockland Standard Gear and install it BEFORE it blows up. Sorry it couldn't be better news, Transman

[jigfeett]

thanks no worriesIt shifts and drives just fine but just has the popping out issue. It kind of makes a sound like a zipper not so much a grind, like zzzzzzzzzzzzzzzz--- oh well we'll drive him till he pukes and send em off to the ford lot......
thanks

[Transman]

Understood. I didn't mean the trans is going to blow up but you need to know that there is nothing inside to protect the trans except a little magnet. There is no filter of any kind so any metal or pieces of junk that float around can easily get caught between the gears. They are hardened steel which makes them brittle adding the close tolerances translates to broken gears without much warning. Good luck and we will pray for a long long life. Transman

[jigfeett]

thanks
where do you work out of?
is there a place that I may find an exploded diagram of this trans>
Thanks

[Transman]

I'm in Southern Zoo Jersey. You could join Alldatadiy and get exploded diagrams as well as specific repair data. Transman