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Question from Tony (1961):
I am having problems with my '61 iron Torqueflite transmission.
I have put it in the shop twice recently. Firstly for a broken reverse band, then I had to return it for shuddering under a heavy load caused by low pressure.
Now it seems I may have another problem. Yesterday, I started to get severe shuddering and clanking when I slowed to a halt. As soon as I applied power, the car ran smoothly. The shuddering only occurred just as I was coming to a stop. The sound was coming from the area of the gearbox. It sounded very much like a loose propshaft or a broken U.J. but having removed the shaft and examined it this morning I am sure now it was not to blame. I also know it is not a brake problem.
Just to confuse things even more, the shuddering went away after I parked the car (but before I removed and refitted the propshaft) and now the car is running perfectly.
I want to call the shop which fixed it but before I do, it would be handy if I had some idea where the problem lies and if this is really a transmission fault.
Last year I had a similar problem with a Torqueflite I overhauled; it happened only in R when I tried to go in reverse on idle. If I run a
little faster (750 - 1000 rpm) the shudder was most noticeable with loud "clung" but if accelerated higher (more than 1000 rpm) the shudder disappeared. But it was not very easy and safe to make a reverse at high speed !!! I had no problem in forward range.
I had to overhaul the transmission 3 times!! First I thought there was something wrong with the rear clutches (too much play) but the 3rd time, I took the pressures and the line pressure was too low in R (but normal in D). The pressure in R is twice the pressure in D and at low rpm the worn front pump couldn't give more than D pressure (the regulator valve worked fine) . The only thing that cured the problem (at 80 %) was to take the front pump to a shop to re-surface it.. I think that the 20 % remaining was some leakage in the transmission, it was too worn.
Assuming all other things (engine, prop. shaft, U joints) are OK, it seems that at low rpm your line pressure is too low and can't hold the clutches engaged. Did you try in R? Try to check the line pressure (or tell it to the shop) with rear wheels off the ground and the transmission in D. You must have around 90 psi (more than 200 in R) at 1200 rpm.
My '56 seems to be doing the same thing, but only very rarely. Heck, I only drive it rarely!
The first time it happened I thought that the emergency brake was grabbing. I had paid a shop to adjust it, and it was after that that this problem started. I re-adjusted it, and the problem went away for a couple of years. The last time I drove it around the block it happened again, and I haven't driven it since. That was about ten years ago.
I have other issues to deal with on that car, like the brakes, so I will be watching for posts on this as well.
It only happens when coming to a stop, and it is a violent shaking. If Tony has checked out the brakes and that is NOT the problem, then I will be looking for the source of this as well.
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