1994 Chevy P30 shift interlock hanging up

[dalejohnson2000]

I have a 1994 MotorHome on a P30 with a 4L80E. The shift interlock mechanism is not releasing every time.
Mash the brake, solenoid engages every time.
Can shift P to R every time.
It was sometime but now most of the time it won’t shift past R to N.
When it does it is smooth to D1 and up to P. It moves fine back and forth as long as I don’t pass N.
The process is
Press brake try to go to D
Hangs at R
Back to P
Brake off
Brake on
Shift to…
Eventually it goes past R and moves smoothly.
It’s not like a jam. It feels like it hits going to N just as it hits R trying to shift without the brake mashed.

I can reach the cable and pull it back down, push it upwards. No improvement. Relieving the tension should release the shift interlock.
I’m thinking if I could get to the slide point up in the steering column I could lube it. At worst remove the catch all together.
Disassembling the column appears to be the only for sure way to get there. Big pain in the buttocks it appears.
Any thoughts?

 

[dalejohnson2000]

I have a 1994 MotorHome on a P30 with a 4L80E. The shift interlock mechanism is not releasing every time.
Mash the brake, solenoid engages every time.
Can shift P to R every time.
It was sometime but now most of the time it won’t shift past R to N.
When it does it is smooth to D1 and up to P. It moves fine back and forth as long as I don’t pass N.
The process is
Press brake try to go to D
Hangs at R
Back to P
Brake off
Brake on
Shift to…
Eventually it goes past R and moves smoothly.
It’s not like a jam. It feels like it hits going to N just as it hits R trying to shift without the brake mashed.

I can reach the cable and pull it back down, push it upwards. No improvement. Relieving the tension should release the shift interlock.
I’m thinking if I could get to the slide point up in the steering column I could lube it. At worst remove the catch all together.
Disassembling the column appears to be the only for sure way to get there. Big pain in the buttocks it appears.
Any thoughts?

We’ll this afternoon I dig deeper. Got it!
So if you have similar situation.
There is the steering column shifter interlock solenoid and the mechanism that could prevent the shifter movement. I think it would have to be no movement or total movement. Not partial like I had.
So fiddling around with it I could feel the blocking was lower on the column.
Went under the vehicle. Looked up and ther was the linkage connected to the shift cable. And to another yoke link. It went to a gizmo that pressed a button. Lubricated that linkage. Wow!! Smooth as silk shifter movement. I think this is a switch for the stupid AutoBrake. I will add that linkage to my lube list. Later!

 

[dbrannon79]

Glad you found the issue. on my 95 truck it has a full cable from the column to the trans. iirc 94 has the linkage out on the lower area of the firewall with rods to the trans. those tend to wear and bind over time. when you have a change, I would try to get at them and see if the linkage where it connects and all the moving parts or joints for wear.

 

[Will L.]

Just saw this and read question then self answer. Glad ya found it.

If you get a chance to post a pic- it would be interesting to see and might help the next guy.

 

[MrMarty51]

Welcome to TTS dalejohnson2000
I too would love to see pics of the faulty mechanism.
I think My truck is getting ready to cause me about this same style of grief.

 

[dalejohnson2000]

Here are some pics.
This P30 has a motorhome on top of it. Many items are tucked away, like this one. The 2 pics are the same, one with ID colors.
The red circled shaft is the end of the shift yoke, this is where the steering column bolts to the floor, under the vehicle. I can't reach it, it is about 18 inches up into an area that is covered. So I was lucky to have a new can of PB Blaster that could shoot that far straight up.
The top of the pic has a Green circled area, that is the jammed mechanism and the front of the vehicle. The yellow circle is around the yoke link from shifter tube. The red circle is the shift yoke. The Blue circle is marking the shift cable. So the mechanism rotates and encages a button sensor. So it appears that the button is depressed in N, OD, D, 1, 2. So a skeet of the PB Blaster and then a squirt more for good measure.
By the way, when I thought it was jamming in the shift interlock mechanism. I found a way to see what was going on there. Remove the Gear indicator cover, remove the pointer, remove the socket the pointer inserts into. it is held in with a clip, use needle nose pliers to hold onto it so it doesn't drop into the abys. So with it out, look down into the gap on the driver side of the shifter you can see the interlock mechanism. I used the PB Blaster there also. Also was able to move the mechanism with a screwdriver and verify that was not the cause of the hangup. The way it is set up it would jam preventing shifting our to P. Not a partial jam like I had originally.