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Help! G320 Leaps forward - No Reverse - Wadup?

987 Views 6 Replies 5 Participants Last post by  Roly
After a Multi Hour drive at 4000 rpm ....I stop for gas and reverse to the pumps. It feels like the rear hubs "lock up." I fill....I drive away from the pump and the whole drive line shakes.The Car leaps. 0 to 5 mph max. I drive off into the grass...I try everything. Button on/off..all wheel/street. Back up...disconnect the hubs? with and wihtout power.

Something of the above worked and I continued my trip. I return home.

Today It's back!

I go forward and it feels the whole drive line wants to go in every different direction. A "bucking" at low rpm/mph. Nothing above worked.
I return to the NO reverse! The transmission and shift lever seems to be out of phase/alignment. P is Park, N seems like a little reverse, R seems like neutral and yes it does go forward...but still as bucking bronco.

I don't know anything about automatic transmissions. Manual I get.
I dread the "if you touch those buttons on the wrong D E S T R O Y ..the drive line" expensive as 1 2 3.....that'd be One transmission ...two dealerships and three differentials costly.

First things first. What electro/mechanical system disengages the diffs? Is there a fuse/relay involved? Does rolling in reverse put my drive line at risk? Same question after Hours/Speed/Heat?
Does "adjusting the bands" have meaning here?

Any suggestions other than Jerr Dan to nearest Cash Vacumn?

I proudly stand next to this vehicle that I can say GETS ME HOME! 90K mi young, '96 G320.

All thoughts, hints, tips appreciated. I'll be reading repair and maintainance manuals until someone points me in the right direction here.

Thanks in Advance.........Bill in Boston
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G320 Vibration - No Reverse - Anybody?????

Shift Cylinder?? what makes it move in and out?
Trans Oil Level is Correct
Shifting Linkage seems ok @ transmission

Is the shifting solenoid and diff shift cylinder driven by the same hydraulic reservoir and preassure cylinder?

Would a leak or lack of pressure cause these Problems?
RE: G320 Vibration - No Reverse - Anybody?????

Is this the 4spd auto or 5spd?
RE: G320 Vibration - No Reverse - Anybody?????

it's a 4 speed auto G320 - 6 inline with a 104 engine. My cruise was at 80+ mph for over 3 hours. I'm thinking it's a failure of the hydraulic system is lack of release of rear diff ( the cause of shudder )aggrivated by reservoir drop which doesn't allow shifting? Can't seem to find hydraulic pattern for this.
Yes, it got me home, but not enough pressure to build for release of diff and shifting. Make any sense?

no hubs on your truck to lock up
locked diffs will not cause that kind of behavior

sounds like your transmission had a heart attack
MB dealer will tell you whether you need a new one or not - if you are lucky they might agree to repair it

here is more;

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You have the same G320 that I do.
The front and rear diffs engage via electric solenoid (on the drivers side firewall) --> Vaccuum --> Intensifier --> Hydrolic (DOT4 Brake Fluid) --> Slave on Differential (next to pumpkin).

If you want to disable the locks from engaging, disconnect the vaccuum line on the bottom of the solonoids found on the driver's side firewall. You could have a leak in one of the electric soloniods.

The transfer case also uses vaccuum to engage the lock. It is located on (or close to) the center air intake. The vaccuum activates the transfer case lock directly (no intensifier or external hydrolics).

I find it odd that the diff locks would engage without showing the red light on the dash. The light and sensor are completely independant from the rest of the systems.
I tested the "engaged sensor" manually when I was trouble-shooting mine. The red light will show that it's engaged even if the dash switch has never been pushed.

The diff locks should be using Brake Fluid; not oil or tranny fluid.

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Try isolating the gearbox from the drive train . This is easily done by putting the transfer box in neutral. Then put the g/box in drive and see if there are any strange noises as the power turns at idle, if all ok then give it some gentle power. Turn off the engine to stop all shafts spinning and do the same thing in reverse.Don't change from drive to reverse with the t/fer box in neutral as the torque convertor will still spin the shafts in the t/fer box.

Can't really suggest any thing else.
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