C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failure

[Ray K.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

One year ago the shift cable on my 2007 failed. Upon leaving a parking space at a doctors office- when I shifted into drive to go forward the shifter felt " odd " with more movement than usual. I proceeded towards home about 4 miles and stopped at a convenience store near our home. When I started the car again and attempted to reverse, the shift lever moved freely and did not engage the transmission. It was locked in park position.

I then called Auto Club and asked for flatbed transport and to bring some wheel dollies to put under the rear wheels as they would not rotate. After about 2 hours the tow company arrives but no wheel dollies. The driver wanted to physically drag the Corvette up on his flatbed with the rear wheels locked. I declined his services and sent him on his way. As I was near home I called my wife to come and pick me up. I then returned with my floor jack and jacked up the rear of the car. With the car up in the air I was able to use a long screw driver and tap the trans shift lever forward 2 clicks which then put the trans in neutral . The car would now roll - forward or backward. I called Auto Club again and asked for a flatbed truck. When the truck arrived we were able to winch it up on the truck without issue. A short distance to home and we unloaded it Jacking it up again I was able to move the trans shift lever to drive position. The computer thought the car was in park and thus was able to start the car and drive it into the garage.

The next morning I went to Auto Zone and purchased one of the Dorman shift bushing kits. With the tools that Rich described you are able to lift shifter up and out of the console. The nylon bushing on the shift lever end of my cable had deteriorated and the cable was just hanging there. The temporary bushing snapped into position and everything worked as normal. I did go to my Chev dealer that same day and purchase a new shift cable #20782446 which I carried in the car with a few tools for about 2 months. The cable was approx $50 and if you have a dealer replace this cable you will most likely cost you $500.+. One day the shifter did not go into park position easily so I then made an appointment with a Corvette shop here in the DFW area to replace the cable. About 2 1/2 hours on their lift and they were done. If I had a lift would have replaced the cable myself so elected to have it done instead.

This is a poor poor design and a cable with a metal bushing on a stud retained by a cotter pin or clip would be much better. My advice, if you have a C6 Corvette with an auto trans and it is nearing 10 years old, these nylon bushings will fail and leave you stranded when you least expect it. I was fortunate in that I was close to home

Ray

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Ray, I had nearly exactly the same scenario as yours when my shifter cable bushing failed 5 years ago (HERE). It is interesting that the trans end outlasted the shifter end on mine. I'm not sure if it's mileage or time as being the failure factor, or maybe inferior bushing material. Maybe the plastic is simply the wrong type. I'd love to know what is shown on the GM print/spec for that part and run it by a Plastics Expert friend of mine.

I find it unusual about you being able to start in Drive. I recall reading in the CSM that the IMS(Transmission Internal Mode Switch) inside the trans AND the Shifter control selector need to match for a engine start. My IMS failed once and set the CEL(Check Engine Lamp) on and a Diag code on and put the engine in Limp Mode(reduced power). Maybe that happened to you but since you didn't attempt a power drive it never set your CEL or diag code. The IMS on mine was replaced under the Powertrain warranty when it happened.

I agree with your advice about changing the bushing before it fails. Even a inspection would not suffice as one cannot see the entire part without actually removing it. It would likely break if attempted anyways, so I agree..... just replace it. I'm trying to convince my friend with a 2011 Grand Sport that we should replace both of his before they fail.

Rich
PS Do you still have your old cable? I have a idea. I came up with a new bushing design using bronze that I'd like to experiment with, but need a cable, or at least the 2 end pieces. If I could borrow, rent, or buy it that would be great. If not I may just buy a new cable to use. I'd also need a shifter pivot or trans lever pivot. I'll have to look around for one of those. Maybe the trans lever can be bought from GM.

[Ray K.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Rich, Your post prompted me to share my experience about the trans shift cable. In my opinion, this goes beyond a service or maintenance inconvenience, it is, in fact, a prominent safety issue. I think the primary factor is exposure to heat, with age following, and of course more miles means more exposure to heat which these bushings do not tolerate. Regardless of miles, as I said, if near 10 years of age is on the vehicle, " Replace " the cable. Tell your friend with 2011 GS this.

I did not save the old cable. I did look very thoroughly at the new cable, and as you, had thoughts about replacing the nylon bushings with bronze. My conclusion was that it should be fairly easy to install new bushings, but, my concern was attaching the bushing to the pivot stud. Were they long enough for a through hole bushing to accept an external retainer clip on the stud? If not, still doable, but more of a challenge to replace the pivots stud / pin.

Thinking back on starting the car, I believe I jacked up the rear, started the engine, set the E brake, and then tapped the trans shift lever from neutral to drive, lowered the car, and then drove into the garage. It all worked. The shifter lever had stayed in park position so did not trip a code for the ECM and after replacing the bushing all was normal.

Ray

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Rich, Your post prompted me to share my experience about the trans shift cable. In my opinion, this goes beyond a service or maintenance inconvenience, it is, in fact, a prominent safety issue. I think the primary factor is exposure to heat, with age following, and of course more miles means more exposure to heat which these bushings do not tolerate. Regardless of miles, as I said, if near 10 years of age is on the vehicle, " Replace " the cable. Tell your friend with 2011 GS this.

I did not save the old cable. I did look very thoroughly at the new cable, and as you, had thoughts about replacing the nylon bushings with bronze. My conclusion was that it should be fairly easy to install new bushings, but, my concern was attaching the bushing to the pivot stud. Were they long enough for a through hole bushing to accept an external retainer clip on the stud? If not, still doable, but more of a challenge to replace the pivots stud / pin.

Thinking back on starting the car, I believe I jacked up the rear, started the engine, set the E brake, and then tapped the trans shift lever from neutral to drive, lowered the car, and then drove into the garage. It all worked. The shifter lever had stayed in park position so did not trip a code for the ECM and after replacing the bushing all was normal.

Ray

Ray my idea will work without modifications to either the cable OR trans/shifter lever pivot ball studs. At some point I'll run up my lathe/mill and experiment with aluminum stock.

I just ordered a cable. I now need a pivot ball stud from a old shifter or trans lever, then I'll be all set for my experiment. I may have to scour the web for some junk parts, or buy a new trans lever from GM. If it works out I am going to modify the cable on my own car and do "trials" testing.

Rich

[James G.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

You're something else Rich; all that pressure on wifey's birthday, working with a Rube Goldberg jacking setup, doing a "gravelback"adhoc repair under a running car and fighting the vehicle's "smart" safety computer brain and STILL took pictures. My hat is off to you guy...

YOU ARE THE MAN. And all at this pandemic thrown in. HAPPY BIRTHDAY Cathy.

[James G.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

DO 1996 C-4'S have a similar problem?

[James G.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Thank you. I am glad it is not a safety issue as the C-6 cars.

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

YOU ARE THE MAN. And all at this pandemic thrown in. HAPPY BIRTHDAY Cathy.

Jim, I read your post to her last night and she had a big grin and asked me to say "Thanks!!!"

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

......I just ordered a cable. I now need a pivot ball stud from a old shifter or trans lever, then I'll be all set for my experiment. I may have to scour the web for some junk parts, or buy a new trans lever from GM. If it works out I am going to modify the cable on my own car and do "trials" testing.

Rich

I found GM still has the transmission lever available so I ordered that yesterday, due next week at around the same time the cable will arrive. Actually I ordered 2 levers. I will make a mockup "shifter" and "transmission" on the bench with the new cable. This will allow me to test my bronze bushing idea much easier before implementing it in the car.

I got a roll of exhaust pipe insulation wrap from my local NAPA. I plan to wrap the left pipe over around a foot or so of its length below the trans lever/plastic ends/bushing.

I also may add some at the forward pipes on both sides below the center console area to help reduce some of the heat in the enclosed shifter area. Remember that end bushing also failed 5 years ago. Wrapping those areas may also help reduce heat in the center storage bin and cupholders. This is a common issue with C6's so it may help.

Here's the wrap 2"x15', Thermo Tec 735-395. It uses SS zip straps(sold separately) to hold it in place. I have used their products before, are high quality and "MADE IN USA".
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Their starter motor wrap works great on the C2 big block cars I've restored.
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Rich

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[Richard S.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Evening....As I was reading your article the other night, a friend stopped by, so I put my computer down, and he proceeded to tell me how he started his C6 (auto) but it would not go into reverse or any gear. I did a little chuckle and told him about your article that I had not quite finished, but sure sounded like he has the same problem. I am going over to his garage tomorrow to take a look to see what is going on with the shifter cable. If it is the plastic bushing I agree that heat is making that part brittle allowing it to break. After he left I finished your article and started to thinking that yes the replacement part will correct the problem, but in time it will occur again, so what I was wondering and thought I would pass it by the jury, do you think that if I was to 3D print that part out of carbon fibre, would that not make for a better part? It is not my car but I would sure like to give it a try. The part pictured on the red background is that the only piece you replaced? Did you remove any of the console or were you able to replace the one at the back with everything in tact working under the car at the back? Thanks for your help and let me know what you think about the 3D print idea. Ric

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Evening....As I was reading your article the other night, a friend stopped by, so I put my computer down, and he proceeded to tell me how he started his C6 (auto) but it would not go into reverse or any gear. I did a little chuckle and told him about your article that I had not quite finished, but sure sounded like he has the same problem. I am going over to his garage tomorrow to take a look to see what is going on with the shifter cable. If it is the plastic bushing I agree that heat is making that part brittle allowing it to break. After he left I finished your article and started to thinking that yes the replacement part will correct the problem, but in time it will occur again, so what I was wondering and thought I would pass it by the jury, do you think that if I was to 3D print that part out of carbon fibre, would that not make for a better part? It is not my car but I would sure like to give it a try. The part pictured on the red background is that the only piece you replaced? Did you remove any of the console or were you able to replace the one at the back with everything in tact working under the car at the back? Thanks for your help and let me know what you think about the 3D print idea. Ric

Ric, Your friends cars' symptoms, as you described, actually could be one of several potential faults, but it depends on more detailed information to diagnose which fault.

Condition 1: Failure of the Shift Interlock System.

When he started the car it must have been in Park. With foot on the brake, a Control Module triggers a relay which energizes to activate the shifter safety solenoid(in the shifter console) to allow a gear change. If one of those circuit sequences is faulty then the car will not allow the shifter to move out of Park. The fault could be the Module, the relay, or the solenoid, but one other item....

There is a pawl that the solenoid moves to allow shift from park when pressing the shifter release button located in front of the shifter. If that pawl becomes jammed then the shifter won't move. I have modified my car with a "Emergency Release" cable connected to that pawl and the end of the cable tied in a pull loop and it resides in the center package tray. It came in handy a few times.

The relay is located in the Passenger side footwell and can be seen after pulling the carpet back where your feet reside while seated. You can hear the relay click each time the brake pedal is applied. If suspect you can swap with another identical relay near it in the same panel. BTW I keep a spare relay in the car.

Condition 2:
If the car started and with foot on brake and the shifter safety circuit allowed him to move the shifter into Reverse or other gears, but the transmission did not respond, then yes, either the Shifter end or the Transmission end of the shifter cable has become disconnected, likely due to a "bushing" fault at either end.

The part pictured on the red background is that the only piece you replaced? ........
Yes the bushing pictured on the red shop rag was what I replaced at the transmission end a
nd yes the only part I replaced, this time.

Did you remove any of the console or were you able to replace the one at the back with everything in tact working under the car at the back? ........
No need to remove console this time, thankfully as I didn't have the tools to do that. 5 years ago the same type bushing was replaced at the shifter end due to the bushing failure there. The link to that episode above in Post#1. (Also HERE again) and yes for that one... Glove box, shift console, and HVAC/radio/NAV panel must be removed.

Thanks for your help and let me know what you think about the 3D print idea.........
I'm not familiar with carbon fiber but that may be a viable option.

Rich

[Richard M.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

The new cable arrived yesterday ahead of schedule. The shifter pivot levers are expected Monday so I'll then have the major parts for the replacement bushing experiment.

Here are detail photos of the cable for future reference. The plastic bushings are a semi-hard material. You can push your fingernail on the edges and feel that they are a bit pliable. This must be so they can snap over the pivot lever ball studs. Maybe this is why they disintegrate over time in the hot environment. The part had a white paper label attached but it fell off. MIC*
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Here is another cable from a GMC dealer Parts dept showing the label. I had our GMC Acadia there for a recall Wednesday. I know the parts man very well and asked if I could inspect and photograph it. Interesting that a GMC dealer had a Corvette cable in stock. Hmmmm.
I asked him if they have a lot of cables to replace due to failing bushings on other GM cars/trucks and he said not a staggering amount. I told him he may see many more as the cables age. He is aware that the bushings were never available in service. I told him the C5/C6 Corvettes are getting a considerable amount of failures now.
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Rich

[Richard S.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Thank you for the information Rich will let you know what I find later today.
Ric

[Ray K.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Rich It seems that Ric has good option to offer with a carbon fiber bushing. Regardless, please keep me posted on your results as you have now acquired a new cable to experiment with and design a new bushing. You have more resources than I as I do not have a lathe. Ray

[Roger W.]

Re: C6 - You may need to carry a jack but not for tires, Auto Trans Shift Cable Failu

Rich. You are the best. It is too bad that you had to make this instructional post under such pressure.