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Discussion Starter #1
Just bought a 2000 w/auto, tranny would go into both fwd & reverse briefly after cold start, then would act like it was in neutral. Fluid level was good & fluid looked fine. Dropped pan, no metal or other junk. Tore it down looking for broken parts, the only thing I see is a broken boost valve spring retainer on VB - wouldn't that only affect 4th and TCC? All gears/clutches look good. Bad pump? Pressure solenoids/sensors?

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while your in id replace anything that looks remotely worn. solenoids and sensors would be a good idea
 

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Yeah, at least anything that I might have to R&R the tranny for - pulling the VB isn't so bad. Oh, and what about the OD unit - maybe I better open it up too, in case it's actually slipping there rather than the tranny?
 

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It would have been nice to do a clutch apply pressure test before you tore apart. Could probablly saved you some effort.
the broken retainer should not cause your problem.
A review of boost valve shows that with valve out of it's bore, line pressure would be lost. No line pressure - no go. Sometimes it is best to ask before you leap.
I would have recomended the mentioned test and you would have found the valve upon dropping the VB.
 

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In addition to what dozer was saying, I can tell you its unlikely that the source of the problem you mention is in the OD unit. Theres two clutches in the OD unit that would transmit power to the rear wheels in 1-3 and reverse conditions, which are the OD Direct clutch and the overrunning clutch.
If the direct clutch was to fail(and everything else was fine), you would have all your forward gears, as power was transmitted through the overrunning clutch. But when you put it in reverse it wont go anywhere since the overruning clutch will just freewheel.
If the overrunning clutch was to fail(which is unlikely) and the direct clutch was fine, I think the only problem you would have would be that the rpms might flare up between 3rd and 4th, during the time that the direct clutch disengages before the OD clutch engaged.

In order to lose forward and the problem be in the OD unit, you would have to lose both the direct clutch AND the overrunning clutch. Being as the overrunning clutch is totally mechanical with no frictions, temp wouldnt even come into play.
 

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Discussion Starter #6
the broken retainer should not cause your problem.
A review of boost valve shows that with valve out of it's bore, line pressure would be lost. No line pressure - no go.
I am confused - isn't it the broken retainer that allows the boost valve to get out of position? Or are we talking about different things?
 

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Quote: I am confused - isn't it the broken retainer that allows the boost valve to get out of position? Or are we talking about different things?
end quote
Me bad, poorly written statement.
The retainer breaking was the beginning of porblem. If valve had stayed in place you would have been o"k. But naturally it didn't and as soon as it came out, Line pressure went to near zero. And then no pull.
 
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