47re lost reverse

thatguy69

thatguy69

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Jul 31, 2011
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So I get home from a spirited drive to the parts store last night, go to back into the garage and I have no reverse. I figure something screwy with the low/reverse band as I haven't adjusted it since I built the trans(26k ago) so I dropped the pan today and double checked it and it was fine and so was the servo, pan and filter was also clean as a whistle. Fill it back up and try it again and it backs out of the shop about 15 foot and that's it, so I try 2 low and it backs up just enough so I can park it and then I lose it again.i could feel it trying to grab, almost like a surging but then even that goes away and feels like I'm in neutral. All forward gears are fine and fluid level is good.moved the shifter all around to see if it would finally grab just incase the adjustment was off but it didn't make a difference. I ran out of time to throw a gauge on the low band port and won't be able to get to it until Thursday, so until then it's going to drive me nuts. What's your guys thoughts?
 
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That reverse band could have glazed over. Another issue that will cause no reverse is if the overdrive direct snap ring broke, but usually you’d see that in the pan.


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kole32 said:
That reverse band could have glazed over. Another issue that will cause no reverse is if the overdrive direct snap ring broke, but usually you’d see that in the pan.


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Hmm. Wouldn't I lose forward gears if I lost my od direct snap ring?or could you explain why I would still have forward gears and no reverse if that's the case.
 
Put it in manual low, drive it, then let off the accelerator.
If it feels like you stuck it in neutral, no band assist.
If it drags down, like engine braking, then band assist is there.

At least, that's what I was taught and shown to be true.

Mark.
 
thatguy69 said:
Hmm. Wouldn't I lose forward gears if I lost my od direct snap ring?or could you explain why I would still have forward gears and no reverse if that's the case.
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Last truck I had in the shop lost the snap ring and still had forward gears. The overdrive piston disengages the overdrive direct clutch in overdrive. You’d have clutch material in the pan if the OD direct frictions were smoked or the snap ring let loose. More than likely the band is shot, like mark said, down shift to manual 1 if you have engine braking the band is holding if not, overdrive directs. The front clutch/ direct drum is on in reverse as well, but if you’re not having any issues in forward gears I don’t suspect that.


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kole32 said:
Last truck I had in the shop lost the snap ring and still had forward gears. The overdrive piston disengages the overdrive direct clutch in overdrive. You’d have clutch material in the pan if the OD direct frictions were smoked or the snap ring let loose. More than likely the band is shot, like mark said, down shift to manual 1 if you have engine braking the band is holding if not, overdrive directs. The front clutch/ direct drum is on in reverse as well, but if you’re not having any issues in forward gears I don’t suspect that.
Thanks for the explanation. To top things off I gouged a sidewall so now I gotta get a new tire before I can move it

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Thanks for the explanation. To top things off I gouged a sidewall so now I gotta get a new tire before I can move it
 
The overdrive sprag holds In forward but not reverse if the o/d direct Fails
 
I just had a trans in the shop that did this exact thing and the overdrive direct reaction plate was broke.
 
Well sounds like she's coming out either way then just about. I'm surprised it made it this long honestly as it's had a pretty harsh 2/3 bind and I've been anything but nice to it. I figured I would of lost my intermediate awhile ago.it might be a couple weeks until I get it out, got a couple of other projects to finish first. Hooking up my radiant floor heat is number one right now, I told myself last winter that was the last year I was working in the cold and I'm staying true to that.
 
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Pulled the od unit, snap rings looked good. When I was unbolting the od it was pushing off like it was under tension for about half an inch or so which I thought wasn't normal. Got to looking at my od piston and noticed it wasn't seated all the way but was cocked in the bore, so I pulled it out and found this.i understand losing reverse because of this but why wouldn't I lose forward gears also if the od direct couldn't fully engage?
 

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Anybody have any ideas? Would like to fix why it happened before I put this back together so it doesn't happen again.
 
thatguy69 said:
Anybody have any ideas? Would like to fix why it happened before I put this back together so it doesn't happen again.
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Was the piston seal past the bore ? Also when that piston is applied, it disengages the overdrive direct clutches by compressing the spring and taking pressure that is normally holding the overdrive direct clutches on. That piston also applies the overdrive brake clutches, which is what engages the overdrive shift. So I don’t think that’s your issue unless your overdrive brake clutches are hurt.


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kole32 said:
Was the piston seal past the bore ? Also when that piston is applied, it disengages the overdrive direct clutches by compressing the spring and taking pressure that is normally holding the overdrive direct clutches on. That piston also applies the overdrive brake clutches, which is what engages the overdrive shift. So I don’t think that’s your issue unless your overdrive brake clutches are hurt.


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The od piston would not fully retract into the bore because the alighment dowel was wedged, which I'm assuming would not let the od direct clutches fully engage hence the reason why it felt like it was trying to engage reverse but was slipping bad. The piston seal was not past the bore and I had no previous issues with od engaging. When I built the trans I had 1.80" to the clutch hub and used a .69" spacer which is a little tight for what the manual wants. I now measure 1.83" to the clutch hub. I'm just trying to figure out why the piston is over traveling if everything is within spec? I also checked for slop in the groove of the large snap ring that holds the od assembly in the case, but it was tight with no slop.
 
Here are a couple of pics
 

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How do the overdrive direct clutches look ? I’ve not seen the alignment pins get stuck like that before, that is odd.


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kole32 said:
How do the overdrive direct clutches look ? I’ve not seen the alignment pins get stuck like that before, that is odd.


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I haven't pulled those out yet since I don't have a press handy, do you think I need to? I was thinking since my clearance had only changed .03 since the build and I didn't see any clutch material in the fluid that they were ok?
 
If I was slipping in reverse and the reverse band and drum looks ok. Then yes definitely check them out. Also check the direct clutches. (Front drum that sits on the input)


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