[Rick Schmidt]

I'm working on a 1971 904 Torqureflite that has an unusual problem. When the shifter is placed in "D" the transmission starts out in second gear. This is evidenced by very sluggish acceleration from a dead stop. When the shifter is placed in "1" the vehicle will not move at all. It will make the 2-3 shift at a normal car speed of about 25 to 30 mph.

The transmission has been completely disassembled and refurbished with new lips seals and seal rings in the clutches and servos. The valve body has been disassembled and all the valves are moving freely.

Any ideas on where to look would be greatly appreciated.

 

[ImperialCrown]

Welcome to Allpar. Are all the check balls back in their proper positions in the valve body?
After double-checking shifter and throttle linkages for proper adjustment, the next diagnostic step would be fluid pressure tests.
If you have no 1st gear at all, does reverse work OK?
If Reverse works OK, this might rule out the low-reverse band operation. Reverse uses the Front Clutch and 1st uses the Rear Clutch.
See p. 10 here for testing 1st gear clutch/band pressures:
http://www.uscars.biz/uscars/extras-documents/ATSG_A727_A904.pdf
Make sure that the line pressure is within specs. Also make sure that the throttle (kickdown) and governor pressures vary as described.
An auto parts store may have an ATF (0-300 psi) pressure gauge tool with the proper test port fittings for loan if you leave a deposit, or an inexpensive one for sale. If you know someone who might loan you one, that would be cool also.
https://www.walmart.com/ip/ATD-Tool...62587&wl11=online&wl12=29897850&wl13=&veh=sem
Always diagnose first.

 

[Rick Schmidt]

Yes, the check balls are in the proper positions.
Yes, the shifter and throttle pressure linkages are adjusted correctly.
Yes, reverse works.
I think that somehow, there is pressure the front servo (front band) in the "D" shift positions at breakaway. The 2-3 shift can occur because the front band is released by applying pressure the opposite side of the servo along with force from the servo spring.
When in reverse, there is no hydraulic pressure applied to the 1-2 shift valve, the 2-3 shift valve, the shuttle valve, the 1-2 shift control valve and the kickdown valve. So therefore, the front servo is not engaged in reverse.
When I disassembled the valve body, I expected to find the 1-2 shift valve stuck, but it moved freely. In fact, all the valves moved freely.

I considered that either the throttle pressure is too low and/or governor pressure is too high, but that is inconsistent with the 2-3 shift occurring within a normal vehicle speed.
What really baffles me is that the vehicle will not move in the "1" shift position. Granted, the manual valve opens up other circuits within the valve body in the "1" position compared to "D." But fundamentally the difference between "D" and "1" is the rear band is applied in "1." Same function as the overrunning clutch.

Regardless, I agree that pressure tests are in order. I was hoping that someone out had experienced this situation.

BTW: I was a Dodge mechanic from 1970 to 1982 so I am quite familiar with this transmission.

 

[ImperialCrown]

Cross-leakage can occur and apply the two (front and rear) clutches together. This will act as a 'brake' in 1st gear, but would be fine for 3rd. Front Band 'apply' pressure in 1st may also feel like starting out in 2nd.
The front pump reaction rings must seal on the inner hub of the front clutch.
A hydraulic pressure test with a gauge would verify both of these conditions and is still the best method of diagnosis here.
If the transmission has been gone through and rebuilt, the reason for this malfunction is hopefully something simple, even if the transmission has to come back out to fix it.

 

[Rick Schmidt]

You are close, but just a bit off. However, the comment you posted above caused me to think in a new direction.
The front and rear clutches are applied in third gear, so there is definitely no lock up. However, if the front and rear clutch are applied AND the rear band is applied there will be a lock up. I now believe that the root problem is that the governor valve is stuck open causing the transmission to operate in third gear. Fortunately, the governor can be tested per the procedure in the document you sent me.

I'll be back when after I have an opportunity to work on the car this week.

 

[ImperialCrown]

Governor pressure should be proportional to tailshaft speed, 1 mph = 1 psi, etc.
I have come across stuck governors before.
A quick and dirty attempt to free it would be to throw it in Park at a speed above 30 mph for a brief second.
The resulting 'z-z-z-z-z' pawl/sprag vibration sometimes dislodges the governor shuttle valve and the governor will work properly after that until the next time it sticks. They can be intermittent.

 

[Bob Lincoln]

I'd hesitate to do that. A kid did that to his 73 Satellite on purpose when I was in HS, at 40 mph, and he snapped the park pawl, and ended up with effectively two neutral positions.

 

[ImperialCrown]

There was a discussion on this in another governor related topic here. There is 2 sides of the fence with this procedure.
I will leave it up to the OP.

 

[Rick Schmidt]

I elected to not try shifting into park while driving the car. I did that accidentally to a truck I was working on long ago. No damage but the noise scared the [email protected]#$ out of me.

Pressure tests came out within normal range. The governor did indeed respond in a linear manner, starting out at zero and ramping up as the speed increased. So, my latest theory that the transmission in always in 3rd gear is out the window. The trans is coming out the car for another look inside. I'm completely baffled by this one.

 

[Rick Schmidt]

I found the problem once I disassembled the transmission. The front clutch has blown outer lip seal on the piston. And the friction discs had no friction material on the and they were fused to the plates with a varnish like material from overheating. What was really odd about the blown lip seal is that it was partially pushed out of the groove in the piston as if it had been forced out by hydraulic pressure. In other words, the lip seal was on the underside of the piston. I've seen lip seal ripped and also flipped over so that it was above the piston but never like this.

Anyway, with the lip seal out of position, I'm sure that the front clutch was engaged at all times. Since the rear clutch is engaged in all forward gears, this means the transmission was indeed in 3rd gear all the time. Putting the selector in "1" would engage the rear band thereby holding the ring gear of the rear planetary unit and locking up the transmission.

The lesson here is that previous experience, diagnostic tests and a detailed analysis of the hydraulic schematic did not pick up the problem. I may not ever see this again, but I won't forget it.

 

[KOG]

Just goes to show that anything is possible. How may be a mystery forever.