55 dynaflow clunck in reverse

[Guest bakersfour]

I have a 55 special with a dynaflow.. when I put in reverse I get a pretty good clunck. what should I look for

[PONTIAC1953]

i would look for a worn out u-joint in the torque tube driveline.

[old-tank]

Look for a worn out u-joint in the torque tube driveline last. They all clunk some, especially if the idle is fast. Try it at ~500rpm. Be sure the engine and transmission mounts are in good shape along with the thrust pad. Try these things and get back us.

Willie

[NTX5467]

From what I've seen, almost ALL automatics from back then have some "clunk" or "harsh engagement" when going into reverse. Mechanically, I believe there is not an accumulator in the Reverse fluid circuit to cushion engagement as there is in the "forward" fluid apply circuit. I know that many later-model automatics are this way.

To further cushion engagement, later models can use "wavy" steel plates in the clutch packs rather than "flat" steel plates. In the case of TorqueFlites, the flats were last used in '65 model trans. I have a friend who always "retro-fitted" his later model TFs with the '65 steels. IF you knew what you were feeling, you could tell a difference in a slightly-firmer engagement and shifts. Most people would not notice it, but we did.

I tend to suspect that if it was a u-joint issue, you'd have clunks during cruise-to-coast throttle transitions, and vice-versa, NOT just upon Reverse engagement. NOT to rule out u-joint wear completely, as there probably could be some, but there are MANY other easier and more-readily-available things to check first! NOT to forget the base idle speed, idle mixture adjustment, and base ignition timing . . . all of which are much easier to deal with than a u-joint issue! Old rubber mounts are in that mix, too, as Old-Tank mentioned.

Please advise of what you found.

Regards,

NTX5467

[1953mack]

I have a 55 special with a dynaflow.. when I put in reverse I get a pretty good clunck. what should I look for

A 1955 Buick Shop Manual.....

Al Malachowski

BCA #8965

"500 Miles West of Flint"

[bhambulldog]

Mine has been clunking into and out of reverse for 40 years,

You'll het used to it..

[JohnD1956]

It's very tempting to start these old Buicks and want to drop it into gear and go. But there's a good chance of dropping the reverse band strut if the engine is running too fast as you put it into reverse. The best thing seems to be to let it warm up so the fast idle is out of the picture and also to get the warm engine idle down to between 450 and 600 RPM.