OT '90 Bronco tranney trouble

The only element in the A4LD which is peculiar to the O/D gear range and no other is the overdrive band. The only time it is used is in the O/D selected range. The High & reverse clutch and the forward clutch are also used in the O/D gear range but they are also used in the other gear selections and Ray has said that the other gear ranges work fine. So the likely culprit is the O/D band either being worn out of out of adjustment. The O/D one way clutch and the one way clutch are not used in the O/D gear range.

The adjustment for the OVERDRIVE BAND is to loosen the lock nut and with it loose tighten the band adjusting screw to 10 Ft.Lbs. (14N*m) of torque. Once it has been torqued then back the screw off 2 turns and tighten the locknut. Be careful not to let the locknut interfere with the initial torque setting. ALSO be careful to hold the adjustment screw so it doesn't rotate from the adjusted setting when doing the final tightening of the locknut. The locknut torque is 40 lb. ft. or 54 N*m.

Also don't just spin out the adjustment screw willy nilly or you could have hard parts falling out of place internally which would necessitate tearing down the transmission.

There is also an INTERMEDIATE BAND and the adjustment is the same for that one except that the number of turns which it is backed out after torquing to 10 Ft.Lbs. is 2-1/2 turns.

If the OD sprag is blown, when you put the shifter in OD you ain't goin no where cause nothing is locking up the OD planetary, ring gear and shaft, which also serves as the input shaft to the back (C3) part of the tranny.
When you shift to D
Now on come the coast clutches, they hold the planet, ring gear and shaft. Life is good, and
now there is input to the back of the tranny. Then, after he's in 3rd, he moves the shifter back to OD and on comes the OD band, off go the coast clutches, and bang,zoom,pow, your overdriving the planetary and off you go in 4th gear.
I'm bettin that when he comes to a stop he has to pull the thing back into a lower range to take off again.
Adding the coast clutches when shifted manually into a lower gear, is common Ford. They figure, if your shifting down, you're pullin something, and they want to give you the extra holding power. Come to think of it GM and Chrysler do similar things.
The problem is that the coast clutches are pretty weak commonly only a 2 friction 2 steel pack. Which is why it ain't gonna last forever with that sprag blown. They went to 3 for a while behind the 4.0, but now have went back to 2 in all applications 4R/5R55E. (cost thing).
This is why I believe it's the OD sprag. Gov problems, sealing ring problems,burnt fwd or direct clutches,broken or misadjusted bands would give you other symptoms. If you've seen those metal caged sprags, and how loose fitting they are form the get go (which I'm sure you have), I think we'd all agree that Ray did something pretty right to get 220,000 turns out of a slightly built up, OD version of a Pinto tranny. Just felt the need to get alittle technical, not trying to step on anyones toe. Brokenwrench

Know what you mean about "wanting to get technical".

After a feller spends a lifetime learning all those systems that drove their inventor totally "foaming at the mouth" insane in the first place, it does one good to spout it out once in awhile.

I think it is some sort of a relief valve. :>)

Allan

Brokenwrench is the resident tranny expert, but it seems to me on that one, you might be able to tighten up the bands.

Also, along about those years, Ford had a problem with the governor valve sticking. It might be trying to start out in 2nd or 3rd gear and can be cured with just a little crocus cloth on that valve so that it will slip back under it's own spring pressure.

Hope Brokenwrench jumps in here.

Allan

The more I think about it, I'll just bet that governor is your problem with that many miles. The valve and flyweight is steel working in an aluminum housing and they tend to wobble out.

Might have to buy a new governor assembly. Under $30. Bad news is you have to yank that transfer case to get to it.

Allan

The other item that this thing was famous for was wearing of the forward clutch cylinder rubber lip seal ring.

In either case they both require a complete teardown and rebuild.

By the way, that transmission started out as a C3 (three speed) in the Pinto in the early ‘70’s and was morphed into what is now the 5R55N, E & W (5 speed).

That's why I always like the GMs. They used lipped seals just about everywhere and they would fail like clockwork. Kept me busy for many years. :>)

Ol' Henry had it right when he used the square-cut seals. Pretty darned tough trannys.

Allan