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Need help on 55 Dynaflow


buickbrothers
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I got not response on my last post on this and I'm really stuck. The part in this first picture came from the location circled in the second picture. I haven't found any exploded drawing with this part and the Shop Manual indicates nothing. Someone was into this tran before me and didn't put parts back on correctly so I'm looking for anyone to validate that this part does go in the picture location indicated. It just doesn't seem right for this to sit on top of the reverse band without being secured in some way. Help! Thanks.

Clip.jpg

Parking Lock.jpg

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Is that the reverse band strut? If so it does not have bolts to hold it but it is, for lack of better words, wedged into place between the trans case and the reverse band. It can be displaced by excess torque in reverse like by dropping the trans in reverse when engine idle is too fast. 

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Hi John. It appears to be but it's not in any books, parts lists or diagrams I have which is why I was looking for confirmation. My pre-disassembly picture is my only reference. I don't get the cut outs on the part because it's a real sloppy fit and doesn't seem to align to the housing wall to be in line with the cut outs. Also not the tab riding on the edge of the housing in the pic. Is it really suppose to stick up out of the cavity and ride that edge or should it be in the cavity? Frustrated for documentation but these 55's had gapping holes or really detailed in some areas. Thanks for the help.

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The only comment I have is, it sure looks like it fits there.  I should clarify that I know little about the interior of the Dynaflow.  I would recommend trying to get ahold of @Mudbonethough.  I know he completely rebuilt his 55 dynaflow and is meticulous about taking pics.

 

He also has videos on youtube of the complete rebuilding process.

 

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My wild guess is that you have a home made reverse band strut.  My parts manual has a typical dynaflow diagram from which this small subset is taken

 

20210826_155650.jpg

 

Part F is the band anchor and part T is the reverse band strut. The part number for the reverse strut is the same from 48 to 57 according to this:

20210826_160356.jpg

 

I have to wonder if a prior rebuilder tried to make a reverse band strut that couldnt be dislodged so easily. 

 

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So a little more information. There were what I would describe as two stress cracks/metal tears on the body of the housing at each corner of the housing bridge that the anchor arm feeds under. When I mount this part in, the anchor are sticks up slightly above the cavity it's in which is preventing the servo and valve body to not mount flush/flat when I lay it on there. There is a strut mounted under the anchor arm and lever that matches to the picture/instructions in the shop manual. The instructions only define removal of this one strut under the anchor arm which is done simply by raising the lever and it drops out. I had a spare housing so I didn't reuse the one with stress cracks. It seems this was caused by this part being mounted per the picture and the previous person torqued the servo/valve body resulting the metal housing splitting/cracking. I would love to talk to mudbone but I haven't been here long enough to contact directly. I watch all his videos on the same year/tran and never saw this part.

    

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So John, that strut you have in the diagram/pic is the one mounted under the anchor/level. I don't see this other part in you book as well. It just doesn't seem like it should go there based on everything I described (cracks, causing flat mount problems of the servo/valve body, etc.).

 

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My W.A.G. is it’s an extra part someone put in or a gauge that fell in. Seems odd a dynaflow piece-part would say pat pending on it to me.  If it’s not in an exploded parts list or PSB why would it belong anywhere….what happens if it’s left out?  Just thinking out of the box no pun intended 🙄

 

FWIW it wasn’t obvious from any shop manual picture.

 

https://www.hometownbuick.com/1955-buick-variable-pitch-dynaflow-transmission-maintenance/

 

Scroll to bottom of above link - there are 3 exploded diagrams of various subsystems within the 55 transmission. Didn’t see that part anywhere but please verify. Me thinks so it’s a tool or gauge of some sort that fell in and went along for the ride….

Edited by KAD36 (see edit history)
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Thanks all. I am in touch with mudbone now and he's helping to investigate. It is not an original part for sure and it was not in his 55 tran when he rebuilt - have his original video that he resent. Mudbone thought: "it may be a part a trans re-builder developed. My brother had a neighbor that had a trans rebuilding shop back in the 60's. He had patents on many trans tools and parts". 

 

So, I think we are all in agreement that it's not an original part to the tran. Thanks for verifying and giving me peace of mind! Even if I wanted to, I can't reinstall it without modifying it. It's forcing the anchor arm to protrude and I truly believe it was the cause of the stress cracks in the pic below. I might want to install it if we can determine what problem it was solving. My guess is that it prevents the reverse band from slipping around in the opposite direction as it takes up the open space between the anchor arm and trans housing wall, acting as a wedge. BTW, it can't be installed without intentionally placing it in it's position at the same time of the anchor arm/lever/strut install since it slides under the anchor arm.      

Housing Cracks.jpg

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  • 8 months later...

Not sure if you ever got an answer on this but that part is a repair part (aftermarket) to repair a broken reverse band anchor. The factory anchors had a history of breaking and causing reverse to be inoperable. That metal part wedged into the reverse band snd made it work again. 

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