Technical > Dan Dishon's Transmission Den
Powerglide Questions
JEFF/21C:
tcoupekyle IS RIGHT! You should feel the convertor i have used 9.5, 8 , and 7" convertors and you feel the engagement if it's too tight you can't get a proper idle
lake_harley:
Well, my FED now has about 20-22 (1/8 Mi.) passes on it. We were at a nostalgia 2-day thing at Sikeston, MO on Friday and Saturday. Overall things went OK I suppose. I was very pleased that the car and even the "lollypop" trailer I built got a lot of compliments.
It was mid to upper 90 degrees and at one point when I called a nearby airport the density altitude was 2500+ Ft, even though the track is at about 450. I guess that might explain why the car seemed to get slower as the day(s) wore on.
On the last pass the time and speed were MUCH slower and when it came back to our pit the driver said it didn't shift when he popped the lever from L to D. We jacked up the car and ran it it 1st and hit Drive and it seemed to shift OK. Did it again and it didn't shift. Made a quick check of the shift cable adjustment and when the shifter is in Drive the lever on the transmission is solidly in the detent. Fluid level is OK and the fluid was only about 135 degrees and didn't smell burnt.
I haven't gotten around to checking anything else, but plan to check line pressure and drop the pan to see if there's anything in there that shouldn't be. A quick look in the Powerglide book by Munroe suggested that the sluggishness/dragginess we always have experienced in low might be a leaking low band servo, and if I read right that might also affect application of drive. Does that sound right or possible? I would be a happy camper if the problem didn't go any deeper than the servo!
I welcome any suggestions of what might be the problem. I'd rather not experience the joy of pulling the engine and transmission (again) to completely go through the transmission. >:( I'd rather wait to freshen/rebuild it in a few months when there's no racing.
Thanks
Lynn
tcoupekyle:
I don’t have much insight but I’d check adjustment on the band.
JEFF/21C:
I used TCI servo like I stated in another post checked band adjustment about every six runs other than that, I didn't have many problems
lake_harley:
I pulled the low band servo today and found a tiny chunk of something that was attracted to a magnet....on the spring side of the servo piston. Didn't find the source of the small piece. The piston ring on the servo piston was in great shape and no scratches or other damage in the bore of the case. Pulled the valve body down, managing to knock over the drain pan and dumping about 2 quarts of ATF on the floor, and double checked all of the spool valves for smooth operation. All seemed good.
I had converted the valve body to manual operation using the installation instructions for a TransGo kit by using a 1/4" long piece of tubing under one of the valves....shift valve I believe. Double checked the length at exactly .250" to be sure it was right.
I don't have a trans brake (just foot brake the car) and instructions on installing a shift kit said to install the vacuum modulator but not to hook up a vacuum tube to the intake. Check. It is an adjustable vacuum modulator and wonder if it needs to be adjusted in some particular way to make the modulator spool valve operate correctly with a manual valve body? Thought is that improper adjustment might be screwing up the 1-2 shift. I have a 50/50 shot with my guess, but I'm thinking the adjustment should be screwed in to seat "snug" like an idle needle in a carburetor as a starting point thinking that would simulate a low vacuum, high load situation? My transmission is a later one with the separate pin and spring on the tip of the modulator spool. No mention of adjustment was seen in the instructions.
Any thoughts other than to leave racing transmission building to racing transmission builders?
Thanks
Lynn
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