T56 no reverse after rebuild

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belgiquebasterd
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T56 no reverse after rebuild

Post by belgiquebasterd » Sun Mar 01, 2015 4:52 am

2003 5.7 hemi ram, quicktime bellhousing, ACT twin disc clutch, ram srt10 T56 transmission, ram viper srt clutch master, 2009 challenger clutch slave

Transmission freshly rebuilt (by me, first timer so could have messed up somewhere) shifts perfectly when engine is not running, when engine is running shifts ok in all the forward gears, but will not go into reverse. Downshifting is ok in lower rpms but gets progressively harder as the rpm's go up.

Any ideas as to what might be causing this? Internal transmission problem or a clutch problem?? My idea after browsing the web a bit looking for similar problems, is that the clutch is not fully disengaging. When upshifting before the forward gears engage there is a hesitation, which in my mind is the syncro slowing down the gear to match the speed before the gear engages?

The whole setup is a mix of different aftermarket parts and OEM stuff, for example the clutch master is from a dodge ram SRT10 T56 truck, the clutch slave is from a 2009 dodge challenger car, could it for example be that the master cylinder doesn't have enough stroke to fully extend the slave? How would I measure this?

Thanks.

Clutch master:

Image

Clutch slave:

Image

ChevyEFI
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Re: T56 no reverse after rebuild

Post by ChevyEFI » Sun Mar 01, 2015 6:11 pm

If the clutch is releasing and forward gears are drivable, it's not a clutch issue.

If the shifter will not move to the right of the 5-6 gate, it is the reverse lockout and solenoid assembly. Powered, it allows the shifter to move (through the ~) to the right of the 1-2, 3-4, 5-6 gates over to the R- gate.

Code: Select all

1 3 5 R
|-|-|~|
2 4 6 
Troubleshooting can first be done by strongarming the shifter to the right. The lockout assy. has a stiff spring-load preventing this, but it's okay to push right through it. Also, try applying 5 to 12v to that solenoid. If that fails, unbolt (13mm head 8x1.25 bolt) the solenoid & lockout assy. from the tailhousing and wiggle it out. If it's able to shift into the R- gate, replace the lockout assy. The newer ones are smaller and cheaper than the old 34mm units.

If the shifter moves to the R- gate but will not move forward to shift into reverse gear, you have an internal shifting issue. Shifter, lever, rail, selector pin, shift rail, fork, slider, struts etc.

belgiquebasterd
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Re: T56 no reverse after rebuild

Post by belgiquebasterd » Mon Mar 02, 2015 2:27 am

I removed solenoid for testing so it's surely not that. The thing is, when the motor isn't running the trans shifts fine, only when the motor is running the trans won't shift into reverse. I'm gonna try bleeding the clutch some more see if it helps before I dig into the internals of the trans.

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Re: T56 no reverse after rebuild

Post by Dan Timberlake » Mon Mar 02, 2015 8:37 am

I'd check for complete clutch dis-engagement, and if that is excellent, possibly a bent clutch disk.

That has a synchronized reverse, right?
If there is any clutch drag the synchros have to over come the drag before allowing a shift.
As to why it is so bad in reverse, but not forward, perhaps it is because the speed difference is so much greater than in the forward gears.

Some online groups claim air in a hydraulic clutch can cause it, and bleeding the clutch fixed it. I can see if the air prevented good clean clutch release that could be true.

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Re: T56 no reverse after rebuild

Post by belgiquebasterd » Mon Mar 02, 2015 3:45 pm

The clutch slave does not have a bleeder, any tricks on how to bleed this thing?

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Re: T56 no reverse after rebuild

Post by ChevyEFI » Mon Mar 02, 2015 10:43 pm

Looking at the slave, the pressure line points at the top of the slave, so air should travel up the line automatically. Other similar slaves with bleeders have the bleeder at the top so when bled, they shed air out.

Did you establish a baseline air-gap between fully-compressed slave to trans. face distance minus pressure plat fingers to bellhousing surface distance? Some concentric slaves require shimming to correct a too-big gap.

I'm not sure you clarified lateral or fore action of the shifter, but if the lever reaches the R- gate and will start to shift forward, but is stopped, the blocker may not be slowing the gear down.

belgiquebasterd
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Re: T56 no reverse after rebuild

Post by belgiquebasterd » Tue Mar 03, 2015 2:55 am

ChevyEFI wrote:Looking at the slave, the pressure line points at the top of the slave, so air should travel up the line automatically. Other similar slaves with bleeders have the bleeder at the top so when bled, they shed air out.

That's the way I did it, pumped the pedal about 200 times, saw plenty of bubbles come out and it does feel firm and equal reistance all the way too the floorboard

Did you establish a baseline air-gap between fully-compressed slave to trans. face distance minus pressure plat fingers to bellhousing surface distance? Some concentric slaves require shimming to correct a too-big gap.

I did measure the slave preload before installing (using the diagram found on 'ram clutches' website). The slave has a total travel of 1,45"/37mm and the preload when installed is 0,688"/17,5mm, which leaves a 'working travel' off 0,767"/19,5mm. I also contacted ACT clutches and their clutch needs about 0.315"/8mm to fully disengage so in theory I got plenty of travel in the slave. With this kind of slave there is no air gap inbetween the slave bearing and the clutch fingers they are always in contact

I'm not sure you clarified lateral or fore action of the shifter, but if the lever reaches the R- gate and will start to shift forward, but is stopped, the blocker may not be slowing the gear down.

When the motor is running the shifter will not move forward, there is also NOT the usual grinding of the teeth when pushing on the lever. When the motor is stopped I can pop it into reverse no problem.

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Re: T56 no reverse after rebuild

Post by belgiquebasterd » Tue Mar 03, 2015 9:40 am

Update: did some more testing today, I can move the gearshift lever over to the reverse gate without problem, when I then push forward it won't engage reverse gear (no grinding or anything) when I keep a small bit of pressure on and then give it a wiggle it pops into reverse gear without any weird grinding or other noises.

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Re: T56 no reverse after rebuild

Post by belgiquebasterd » Tue Mar 03, 2015 12:44 pm

And yet another update :-): I contacted ACT clutches asking how much slave bearing travel is needed for the clutch to fully disengage. According to them it needs .280"/7,1mm to .315"/8mm to fully disengage. I 'measured' how much my clutch slave moves and it looks not to be moving more than .240"/6mm give or take, so it's right on the engage/disengaging point unfortunately.

My question now is what causes this I can think of 2 things:

- clutch not properly bled down. I did follow factory recommendations on how to bleed this type of clutch and the clutch pedal has a firm and uniform feel all the way through the stroke. Any tips on how to bleed this type of bleederless clutch slave?

- mismatch in parts between the 2004 dodge ram SRT10 clutch master and the 2009 dodge challenger clutch slave. Could it be that the ram master does not have enough stroke/oil volume to fully extend the challenger slave?


Thanks for the help


Video measuring the slave, black marks are .196" apart.

Image

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Re: T56 no reverse after rebuild

Post by MadBill » Sun Apr 19, 2015 11:12 pm

Does the master cylinder piston retract fully? If not it would limit fluid transfer, as would an undersize (diameter) master relative to the stock one for the slave in question. A clue would be a suspiciously light pedal.
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