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G500 transmission won't shift outta first gear...

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User avatar
Gelande
Posts: 3894

G500 transmission won't shift outta first gear...

Post#1 » Sat Aug 07, 2010 8:12 am

any ideas?

so far we are looking at the Control unit, and valve body....but any other ideas? All other functions work as they should, R, N, P, indicator on dash cluster, and there are no error codes being produced when plugged into the Star machine.

2002 G500 with 5 speed tip

User avatar
Dai C
Posts: 769

Re: G500 transmission won't shift outta first gear...

Post#2 » Sat Aug 07, 2010 8:55 am

I assume there is a control cable connecting the electronics. Pull that off and check continuity of each terminal. I would bet that could be the problem.

-Dai

User avatar
Chris
Posts: 2972

Re: G500 transmission won't shift outta first gear...

Post#3 » Sat Aug 07, 2010 8:32 pm

Two Ideas, one question, does it ever work properly if you turn off and restart repeatedly?

1) Very common for a old/weak battery to cause this type of thing, apparently there can be enough juice to start the engine, but not enough for the TCM to operate correctly.

2) Some type of tasty beverage was spilled into the center console, seeping into the shift lever and/or TCM (transmission control module, which is under the selector lever/cup holder). Try taking apart all that stuff and drain a couple cans of electronic parts cleaner into it, may work fine when its back together.

User avatar
aircruiser
Posts: 488

Re: G500 transmission won't shift outta first gear...

Post#4 » Sun Dec 09, 2018 3:23 pm

Chris wrote:
2) Some type of tasty beverage was spilled into the center console, seeping into the shift lever and/or TCM (transmission control module, which is under the selector lever/cup holder). Try taking apart all that stuff and drain a couple cans of electronic parts cleaner into it, may work fine when its back together.


When the electronic switch part of the shifter if worn or contaminated and the transmission doesn't know electronically what gear is selected it will hold first gear, sometimes after a dramatic lurch when placed in a forward gear(722.6). If you leave the sunroof open in rain, spill your favorite beverage, old age and worn contacts can cause this problem. For me it was old age and worn contacts, only creating an issue with cold cabin temperatures after start on a cold day, slowly getting worse or lasting longer over the last few years. The clues for this problem are unspecified gear indications with Star and the D,4,3,2,1 lights not lighting up when in that gear with lights on, cluster on newer models. On pre-MBUSA models with 722.6 the shifter module can be removed and replaced or rebuilt/regreased and the electronic switch part field repaired or replaced, see photos.
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User avatar
AlanMcR
Posts: 4183

Re: G500 transmission won't shift outta first gear...

Post#5 » Sun Dec 09, 2018 7:03 pm

Thanks for the pictures! Mine is definitely due for a cleaning.
How easy is it to get this switch out? Does the shifter need to be removed first?
Also, was there any contact grease on the sliding contacts? Hard to tell from the pictures.
...Alan

User avatar
AlanMcR
Posts: 4183

Re: G500 transmission won't shift outta first gear...

Post#6 » Sun Dec 09, 2018 7:08 pm

Gelande:
Is it for sure in 1st gear, and not 2nd?

A non-functioning TCU (including no power to TCU) should leave the 722.6 mechanicals in the limp-home operating mode, which is: P-R-N-2 only.

This is an underappreciated reliability feature of this transmission. The TCU can burn up and you'll still get home.
...Alan

User avatar
aircruiser
Posts: 488

Re: G500 transmission won't shift outta first gear...

Post#7 » Mon Dec 10, 2018 6:58 am

AlanMcR wrote:Thanks for the pictures! Mine is definitely due for a cleaning.
How easy is it to get this switch out? Does the shifter need to be removed first?
Also, was there any contact grease on the sliding contacts? Hard to tell from the pictures.

The shift selector is easy to remove from the car, 10 minutes, then the replacement and or serving can performed on a bench.

Removal of shift selector 463 <2002.
Hand brake on, transmission placed in N.
Lift up and rotate TC leather sifter boot.
Remove 1 screw securing the wooden shift/switch panel at the aft end.
Remove transmission shift handle.
Lift up the aft end of wooden shift/switch panel slightly to remove trim ring around shift selector.
Slide the front lip of this panel aft, lift, rotate, and place to the side with wires connected.
Remove 4 bolts securing shift selector to body. 2 10mm and 2 inhex/ Allen.
Remove 3 wire connectors from the shift selector.
Now under the car with a straight screwdriver and needle nosed plier to remove the shift linkage clip.
Remove shift selector to work on bench.

Depending on what service is required on shift selector plan on 10-45 minutes. 8mm and a few small flat head screwdrivers to release plastic clips and use as gentle pry bars. If you are going this far it makes sense to reference the exploded diagram to clean and regrease the mechanism.

Disassemble shift selector.
Place sifter in R.
Remove plastic cover over shift interlock, 2 8mm screws.
Remove wooden shift selector trim.
Remove the plastic PRND4321.
Lift up the electronic shift module and remove to replace or service.
Continue with disassemblely, clean and lube of mechanical parts of shifter, if needed.

The electronic shift module can be split open using small screw drivers to release clips and pry apart. No nasty springs or small parts will go flying out. The contacts on mine pictured has well defined score marks from corresponding spring contacts, I bent those out for increased tension and up for slightly different contact on the circuit board. I hosed down with electronic cleaner, it may be a good idea to put some dielectric grease on the contacts as well? I didn’t notice any grease on disassembly on the contacts. This is a 210 part number, about $120, replacement was my choice, but if you spilled your drink and it just needs a clean?

Reassembly is the reverse. Use the parts diagram. Tip, the electronic shift module has a reference for “R”, align shifter pin and module to “R” on reassembly, placing the pin into Y shaped groove on switch.

Hope this helps.
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User avatar
aircruiser
Posts: 488

Re: G500 transmission won't shift outta first gear...

Post#8 » Mon Dec 10, 2018 7:14 am

AlanMcR wrote:Gelande:
Is it for sure in 1st gear, and not 2nd?

A non-functioning TCU (including no power to TCU) should leave the 722.6 mechanicals in the limp-home operating mode, which is: P-R-N-2 only.

This is an underappreciated reliability feature of this transmission. The TCU can burn up and you'll still get home.


Yes, it is a well thought out design.

In a perfect world with a non-functioning TCU you are correct. In a non perfect world, and with a malfunctioning TCU things seem to get more complicated, sending intermittent electronic signals for other higher/lower gears then locking you in that gear until another signal is received. A simple stop and restart will sort out the weirdness or finding a gear that sends a good signal.

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