Dynaflow drum turning to clean up wear grooves. Is it standard practice?

**joe28704** · 11-30-2015, 08:59 AM

Hi Folks,
Is it "standard practice" to turn down a transmission drum to clean up the surface?
My 52' Dynaflow is coming apart nicely with no signs of damage or excessive wear except the OD surface of the Low Drum.
A Transmission shop in GA indicates they have band linings in standard .045 thickness and thicker .063 stuff meaning the drum could be turned .020 more or less to clean up the wear grooves. When pressed I did not get a definitive answer from the shop that it was OK to take .020 from the wall thickness. Can these drums safely be turned down some and be "made up" with a thicker band lining? My best guess is the drum will clean up nicely with a .005 pass, can I get away with just doing that? I can buy a new drum for maybe $150 or so but I would rather use my original parts if it's OK practice to turn OD.
P.S. I also boogered-up the Rear Bearing retainer sleeve bushing and am looking to find a replacement and/or part number if anyone has a source.
Thanks.

**telriv** · 11-30-2015, 06:25 PM

I wouldn't worry about it. That drum looks fine. Just use some emery to clean it up a little. Don't forget the low & reverse bands are adjustable. For the part you need try "Fatsco". Do a search & give them a call.

**joe28704** · 12-01-2015, 06:51 AM

The "wear" amounted to be just shy of .0025 as measured by trying to slip a shim under the flat.
It is "cupped" by that much. I took It to a local transmission shop and they said the same thing ;dress it up and go ahead and use it.
Thanks for the confirmation.

**BornBuick** · 12-01-2015, 09:14 PM

Great that you are attempting to rebuild the dyno yourself. I will be doing mine this winter. This way you will know it was done right as there are maybe just a scattered few individuals out there now a days that have actually rebuilt one successfully and know how to rebuild these properly. 9 1/2 out of 10 automatic trans shops have never dealt with these units and if they ever did, the talent is retired by now and they took all of their hands-on knowledge, special purpose gauges and tools with them upon retiring.

**joe28704** · 12-03-2015, 10:34 AM

Thanks for the words of support! The internals are surprisingly not as complicated as a modern transmission, was able to completely disassemble it without any special tooling. Now putting it back together........

Be extra careful when removing the rear bearing carrier, it's real real real easy to score/damage sleeve.
Sent the bands to Transmission Crafters in Albany, GA for a redo at $25 a piece, have not got them back yet.
Turned the drum on a lathe and dressed surface with 180 carbide sandpaper and it took out all waviness.

**suntreemcanic** · 12-03-2015, 07:48 PM

I also support rebuilding the transmission yourself. It is so much neater to say "I rebuilt it myself" than to say "I hired someone to do it."

**BornBuick** · 12-07-2015, 05:54 PM

Great…. when you get them back report back and keep up to date. So all the special tools in the manual can be substituted by using just regular shop tools ? Mudbone has a youtube video of his stand and gauge setup for checking the fluid pressures in all phases of operation. He spins the input shaft with a shop made coupler attached to his drill.

**joe28704** · 09-26-2016, 08:57 AM

If it of any help, here is a picture of the coupler and "driver" I used to spin the trans.
The drill had just enough power to create the required appox 100psi to test internal hydraulics.

**BornBuick** · 09-29-2016, 10:18 PM

…. Nice job. Did you check all the ranges D, L & R and did all the readings make the psi mark ?

**joe28704** · 12-13-2016, 01:32 PM

Sorry for delay.
Pressure reading on front pump came up to 90 where it should be. Small handheld drill did not have nearly enough torque to fill an drive the torque converter to get other PSI reading (drill overheats and smokes!) You need a LARGE high amp drill If you check anything more than front pump output.
I had to remove trans 2nd time because valve operating valve adjustment was off not giving me proper shift valve location causing severe slippage in reverse.
Its amazing how more focused one is doing the job the second time! "When clearance is correct, the spring travel at end of shift lever will be 1/8" to 3/16"."
That and the name of my first dog will never leave my memory!
So anyhow, the trans was finally installed and it seemed to go forward and back enough to pull it out of the "deep storage" corner of the basement to the front garage bay (car had not moved on its own since late seventies!)
Next step was to properly tune-up the engine I had also rebuilt and that is the source of my next major problem.
I believe at this point I should open a new thread as it is entirely related to engine performance / compression / vacuum issues.
And so will but briefly, I could not get engine to idle low enough (350 RPM) to set timing, in fact I was lucky to get it down to 700.
Being curious I took vacuum readings at port at carb base to distributor and manifold port to fuel pump (two different gauges) and got sad results of around
10 in.Hg , to go and get further depressed I took compression reading (two different gauges) and got around 68psi average! Book says 120psi min!
If anyone can give me some direction to go with this and other data, I need to have a chat with some engine building people!
Thanks in advance