Tranny Problem

[explicit]

Ok, I was driving along a road, and came to a dead end. I stopped, put the explorer in reverse, and hear a big CLUNK! I never thought much of it and kept reversing. When I came to the beggining of the trail I put it in drive because I was going to go down another trail, but it never drove. In order for me to drive I have to put it in 2nd gear, then when I reach about 1500rpm I can then put it into drive. It's not 4x4 because that does not work. The truck runs smoothly when in drive. What could be the problem?

 

[Blee1099]

Other than the time you put your truck in reverse, did you hear any clunks? Most time when a bad u-joint is suspected, you will hear a clunk when changing from drive to reverse and vice versa.

 

[Opera House]

Does it still work in reverse? Did you try it in manual 1? Did you finally put it in D or OD? D and OD are very different in first gear. Answering these will tell a lot.

 

[explicit]

You can still drive in reverse, Park works, and 2nd works. Other then that you can put it into 2nd, and get it up to about 30 km/hr and then switch it into drive, OD still works also.

 

[Brain]

Does it start in 1st when the shifter is in the OD shifter, or do you have to start in 2nd and then shift up to get into 3rd and 4th gear? Words can be confusing sometimes...OD shifter position vs. 4th gear (aka OD)

The clunk can come from a variety of things, but no 1st gear in any shift selector position while still having 2nd 3rd and 4th means only one thing in the A4LD - the rear one-way clutch (sprag) has failed. You have three options:
1) live with shifting it manually until something else fails (and then do #2 or #3)
2) fix it yourself
3) have somebody else fix it

The rear one-way clutch (sprag) is at the rear of the case, but is accessable only by pulling out the rest of the guts of the tranny - you can't get to it from the rear of the case....sorry to give the bad news.

Here is a really good thread about rebuilding the A4LD (so you can see the part that has failed):
http://www.explorerforum.com/forums/showthread.php?t=98027

There are two one-way clutches in the A4LD tranny, the OD and the rear. Here is a Tech Bulletin about the OD one-way clutch:
http://www.alldatadiy.com/alldata/A.../56351048/34853741/34850750/42063452/42570523

 

[explicit]

Yeah, I turn the truck on, stick the shifter into 2nd, the only forward gear availbable at idle speed, then when I get to about 30 km/hr I can stick it into drive or OD. It is an automatic tranny.

 

[Brain]

Bummer
That rear one-way clutch is engaged in first gear (shifter in 1, D, or OD), so the only way to go forward is to manually bypass first gear by putting the shifter in 2nd...

That one-way clutch isn't effected by hydraulic pressure - it is purely mechanical. Think of it like a hand powered winch where there is a toothed gear and a pawl that keeps it from releasing. The one-way clutch is basically the same except instead of a single pawl it has twenty of them and instead of going "clink" into the next tooth it uses friction and mechanical pressure. If too many "teeth" are slipping, the clutch can't hold and the thing spins backwards.

The good (?) thing is that it is ONLY used in first gear, so the other gears will work normally. A bad thing is that there could be metal particles being circulated around damaging other parts.