Re: OT '90 Bronco tranney trouble

Posted by Brokenwrench on August 02, 2005 at 16:01:17 from (69.128.199.139):

In Reply to: Re: OT '90 Bronco tranney trouble posted by Vern-MI on August 02, 2005 at 13:57:32:

Vern,
I don't want to argue with you, as you seem to know your stuff, but....
The OD band is not engaged til 4th gear. It's just doin nothin til the 3-4 shift happens. On the 93 explorers, the one year they tried the double wrap band, it was common for that band to break. The only result was no 4th. All engagements and upshifts were still normal.
In effect if you left that band totally out of the tranny, all you would do is lose 4th the thing wouldn't even slip, it'd just never make the shift.
Think of the applied elements in each gear.
With the selector in OD
1st- fwd clutches,low roller cl,OD sprag(basically input sprag for GM lovers)
2nd- fwd cl,intermediate band,OD sprag
3rd- fwd cl, direct clutch,OD sprag
4th- fwd cl, direct cl,OD band
Now put the selector in D (3rd)
1st -same except now the coast cluthes are also engaged
2nd- same + coast clutches
3rd- same + coast clutches

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

Follow Ups:

• Re: OT '90 Bronco tranney trouble Vern_MI 04:20:42 08/03/05 (0)
• Re: OT '90 Bronco tranney trouble Allan in NE 16:44:58 08/02/05 (0)

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