T56 Help - No reverse when hot

[1999Black_Z28]

Here’s the situation…my transmission shifts into reverse just fine when it’s cold and I can even drive 50 miles on the expressway (as long as I’m easy on it) and the car will still go into reverse when I stop. My problem occurs when I beat on the car. I don’t have to bang through the gears or anything, just rip through one or two gears and the transmission refuses to go into reverse when I stop. The lockout solenoid is working and allows me to push the shifter to the right but I cannot push it forward to get into reverse. The other gears work just fine and it doesn’t help putting it into first gear and then trying reverse. It also doesn’t help if I turn the car off and try putting it into reverse.

Here’s my setup:
Stock T56 in my 1999 Z28
LS7 Clutch (approx 10,000 miles on it)
Newer OEM slave cylinder (put in with LS7 clutch)
Tick Master Cylinder
Few upgraded internals (1-2 and 3-4 billet keys and bronze pads, 3-4 steel shift fork, Carbon fiber blockers, etc) – approx 15,000 miles

I never had any issues before adding more power (Huron Speed turbo kit). I think the issue is heat related because it will go into reverse again if I let the car sit for a few hours. I’m not sure if the heat is being generated by friction (overpowering the clutch) or if it has something to do with my turbo downpipe ending near the transmission.

Has anyone experienced something similar to this? I have never disassembled a T56 myself so I do not know all of the components and their proper names but is it possible that heat could cause the shift rail to expand causing the reverse fork to bind?

My car is currently in storage but I would like to get this figured out. My plan is to change the trans fluid again (current fluid has 5,000 miles on it) and add more pipe to my exhaust to keep the heat away from the transmission. Is there anything else I should consider? Anything else internal to the trans that could cause this?

[cptinjak]

Does it go through the gate, but the hub is just not engaging? My first thought is the electronic reverse lockout acting up somehow...

Jack

[hoogiesngrinderz]

Hmmm. Did it refuse to engage with the engine off, key on, and hot?

[1999Black_Z28]

Does it go through the gate, but the hub is just not engaging? My first thought is the electronic reverse lockout acting up somehow...

Jack

The solenoid works fine...goes through the gate no problem

Hmmm. Did it refuse to engage with the engine off, key on, and hot?

Correct, when hot it will not engage even with the engine off and key on.

[TORN]

No grinding or any noise?

[hoogiesngrinderz]

I wonder if the solenoid isn't fully retracting when it gets hot. I really can't think of any other reasons that wouldn't affect how 1-6 operate (without grinding anyway)

[1999Black_Z28]

No grinding or any noise?

I've never force it in so no noise or grinding

I wonder if the solenoid isn't fully retracting when it gets hot. I really can't think of any other reasons that wouldn't affect how 1-6 operate (without grinding anyway)

Hmm...You might be on to something. I was thinking the reverse syncro maybe but I cant figure out why it only happens when hot

You rebuild tranny's right? If it ends up being internal would you be interested in picking up a side job?

[1999Black_Z28]

The more I think about this the more I think Michael might be right. I know the solenoid is activating but if it doesn't fully retract it probably wouldn't let the shifter over far enough to go in gear. I will need to wait until spring to get the trans hot again but maybe I can remove the solenoid and see if it goes into reverse when hot. Anyone know how hard it is to remove the solenoid with the trans installed?

[1999Black_Z28]

My first thought is the electronic reverse lockout acting up somehow...

Jack

Looks like Jack might be right too

[hoogiesngrinderz]

You rebuild tranny's right? If it ends up being internal would you be interested in picking up a side job?

Yes, I do manuals on the side. I have yet to go through a T-56. So far I have done Saginaw 4 speeds, Muncie 4 speeds, Borg Warner 4/5 speeds (T10, WC T5, T850)

Technically, unplugging the reverse lockout will disable the solenoid but I'm not sure if will cause the car to run any different

[TORN]

This is some info I found on the net are you sure you are pushing hard enough? Even if the solenoid is bad you can push past it.

The solenoid is spring loaded, so that even if the solenoid fails you can still access reverse, you just have to push REALLY hard on the stick to get over into the reverse gate. What lots of guys do is take the solenoid apart and modify or replace the spring. I cut and re-shimmed my spring until I felt there was just the right amount of force to keep you out of the reverse gate on a hurried shift, but that you could with only modest effot move the shifter over and get into reverse.

[1999Black_Z28]

I'm not pushing hard at all. The shifter seems to go through the gate just fine but now I'm wondering if it is stoping short (when hot). I guess I could try to push harder to the right but I refuse to force it up unless I'm in an emergency situation where I need reverse.

[1BADAIR]

Solenoid is only active above 5mph. So unplugging when key off will disable . Won't affect anything . There is a shift rail on the pass side. Not sure if that heat would affect it . Reverse gear is on the very back . Pull tail housing , speed reluctor the your at reverse. T56 bad to work on. Just a little tricky the first time.
revrse is synconized in a t56. If you pull it apart flip the slider over to the new / nonused side

[1999Black_Z28]

Thanks Larry....I may consider pulling the tail housing to take a look

[cptinjak]

I build T56s and would be willing to fix it for you if you want. If it is anything like the corvettes, I would first make very very sure that the shifter alignment hasn't been thrown off somehow.

Also, is there any reason why the PCM's VSS signal may be compromised? custom wiring, etc? The PCM needs to see a low enough Mph to allow reverse. In the corvettes, stock lockout enables at 3mph and disables at 2mph.

Jack