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Author Topic: A999 transmission shift problem  (Read 1270 times)

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Offline Dieselboot

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A999 transmission shift problem
« on: June 14, 2005, 07:19:33 PM »
Problem is in an A999, three-speed with lock-up. Transmission will shift through all three gears while vehicle is at a standstill (I am not kidding). Gage installed in the governor test port will show pressure climbing slowly from zero in Neutral, to about 24 psi when Drive is selected on the column. Takes about two minutes for the pressure to climb, engine idling, and I can hear the shifts taking place in the transmission. Pressure will drop off to zero again when neutral is selected.

If I take advantage of the zero pressure condition by dropping it into Drive and immediately accelerating, I can get a moving progression through the gears, but once in third the transmission will not downshift or return to first automatically, even when vehicle is brought to a dead stop. It will stay in third gear. Manually shifting through the gears, i.e. starting, from Neutral,  to D1, and moving shifter through D2 and D3 at appropriate points, results in a normal shift sequence.

I have replaced the governor, governor support and seal rings, removed the valve body and worked every spool with jeweler's rouge till it slides without a hitch. Valve body was assembled and installed to manuf torque specs. Manual valve adjustment is spot on. Throttle pressure adjustment has no effect on the symptoms.

In short, this tranny's governor circuit is receiving unwanted pressure from somewhere in the transmission and shifting prematurely. Any ideas?

gen1dak

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Re: A999 transmission shift problem
« Reply #1 on: June 14, 2005, 08:44:13 PM »
Worn or faulty front clutch, kickdown servo band or linkage malfunction, worn or broken reaction shaft support seal rings, incorrect throttle linkage adjustment (you do have the kickdown hooked up, don't you?), aerated fluid, oil filter clogged, low fluid level, valve body malfunction or leakage, or hydraulic pressure too low. Looks like you've hit on some of that already. Good luck.

Offline Dieselboot

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Re: A999 transmission shift problem
« Reply #2 on: June 14, 2005, 09:42:33 PM »
Thanks, gen1dak.

Can't be the front clutch, it shifts normally if I use the selector through D1, D2, and D3.

Ditto the  kickdown servo band and worn or broken reaction shaft support seal rings.

Throttle linkage is hooked up and makes absolutely no difference in the symptoms, no matter where it is adjusted.

Fluid and filter are fresh and properly serviced.

Could indeed be a cross leak in the valve body, but honestly, I think its something simpler, like a misplaced or missing gasket or O-ring. Does anyone know if the governor support requires a gasket underneath? The kit didn't have one and I didn't use one.

Pump pressure output is 280 psi.


Offline Dieselboot

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Re: A999 transmission shift problem
« Reply #3 on: June 16, 2005, 08:40:41 PM »
Well, I didn't get a lot of replies on this one, understandably. The problem is now solved and I'm posting it to benefit anyone else who might be pulling out hair over a similar situation.

The governor support is indexed to allow line pressure from the cooler to enter the high pressure side of the governor. Properly indexed, it also routes governed pressure (variable with driveshaft speed)  to the valve body. My support was installed exactly one bolt hole off, causing the line pressure to feed, with some resistance due to the fit of mating surfaces, into the governed pressure circuit. Result? A false pressure on the governed circuit inducing premature shifts.

Take note: Chrysler cast an arrow mark on the factory governor support to show proper indexing. Some aftermarket parts DO  NOT have an index mark. A little attention here will save you a lot of grief.

Happy bogging.