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THM425 accumulator for reverse?

Started by TJ Hopland, June 28, 2020, 11:15:38 AM

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TJ Hopland

Does the THM425 found in the 68-78 Eldo's have some sort of accumulator or other device to gently engage reverse?  I'm not sure if mine is getting worse or I'm just driving too many newer cars now but my 73 is making a pretty good thud when it goes into reverse.   Doesn't matter if its from park or from drive.   Doesn't seem drive line related.  To me it seems like a muffled clank like its internal but being muffled by the fluid. 

I did have it rebuilt a while back and with all the pan and other leak issues its had in more recent times its had some fluid exchanged.   Doesn't seem to be showing any signs of issues but I recently saw a transmission rebuild video about another GM transmission (maybe a 700) that the re builder was commenting on how someone had eliminated all the accumulators and he said thats bad because it can actually make it damage itself just engaging.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

bcroe

That big band is used for reverse, operated by the rear servo assembly
(in front in an E car).  The band can be damaged, I lost reverse when
it broke.  You can check the rear servo by removing the pan and valve
body, a messy job.  good luck, Bruce Roe