1948 Roadmaster Dynaflow

Hi guys,
the '48 Roadmaster I'm driving has a problem with the Dynaflow transmission. Everything works great with the exception of reverse which will sometimes judder very badly, which I can feel through the whole car when engaged, particularly when hot but at all other times as well. I've replenished Trans oil (Dexion III?) and I have one of those rarities,a Dynaflow that doesn't leak, so no issues. The car is low mileage with 40k from new and has been perfect up to the last 500 miles.
As an added complication I live in the UK and so far the couple of trans rebuilders I have spoken to aren't familiar with the Dynaflow. Can somebody therefore please tell me that this is the easiest problem in the world to fix? - probably not I know! Cheers.

Try adjusting the reverse band. the band adjustments are on the sides of the dynaflow. one is for low and one is for reverse. i forget the sides for which, so someone else chime in if they know.

Hello UK
Perhaps I can be of some assistance. I have just finished a rebuild on a 48 Super/Dynaflow and I'm about to rebuild a 50. This "judder" you speak of could be the "chatter" that occurs when this unit is shifted into reverse. A slight chatter in a 48 was considered "normal". If it is severe you should adjust the reverse band yourself by removing the floormat, carpet and transmission opening pan. The silver cap on the drivers side (Yank Version: left side as you view the dash) is removed and the lock nut and adjusting screw are set following the procedure in the "Buick Dynaflow Manual". I can send you this procedure if you like. Hopefully your band is not too worn as the procedure will not cure this. The best thing you can do first is to pull the oil pan on the trans and see what lies within. This will tell you much about the health of your transmission, despite what the previous owner says. Your statement that you have no leaks is curious as they were designed "to weep" slightly. By the way, while you are at it, pull the plug on the differential cover and check the condition of the fluid.
:rod:

Guys,
thanks to both for replies and advice. Doctorbee - procedure would be great as I have nothing! Just for further info, just came back from two weeks holiday, start the Roadmaster up, straight into reverse and no problem whatsoever, get to work 15 minutes later and fully warmed up car, reverse into parking space and a real, real, bad judder (still reverses though). Spooky!

Cheers
karl

Sounds like it is a slipping reverse brake band. The issue of it occurring when the trans is warm may be due to the dispersion of oil, heat or both throughout the trans, setting you just outside the adjustment limits. Never adjust the reverse band without checking the manual control linkage first. Simple procedure, I'll send jpgs of both procedures (linkage/reverse band adjustment:superseded) for a 48. You can email me by clicking on my user name at this site. Oh yea....pull that bloody trans pan!

Does anyone know how to go about checking the level of trans fluid in the 1948 Buick with Dynaflow?

Easier to send you jpg's of the procedure from the Buick Manual. Send me your email address through this site here.

When draining and replenishing the fluid you have to remove a couple of set screws in the torque converter by manually turning the flywheel to gain access.

Just a thought, if you want to completely clean out your system and start from scratch. It is a troubleshooting elimination process.