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Rear End/Drivetrain Issue

ChevyHDGert

By ChevyHDGert
in Ask A GM Technician

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ChevyHDGert Enthusiast

ChevyHDGert

Posted
Posted

About 6 months ago, I would take off and my driveshaft would spin but the truck wouldn't move. And then after a few seconds, it would lock in and really jerk forward. I recently changed the rear end oil hoping that would solve it.

 

Well, it helped until yesterday.

 

I was cruising on the highway 65-70 mph and had to slow down for a traffic light. I came to a stop at the light, but there was this horrible loud noise and I think it was my driveshaft still spinning, eventhough I was stopped. It did this for about 5 seconds, and then all of a sudden the rear end locked in and made a loud noise and jerk and I initially thought the car behind me tapped me.

 

A little later, I was in the median turning left and I hit the gas but the shaft just spun again and then it locked in after about 2 seconds and jerked me forward.

 

I'm fixing to take it in to the dealer and see if they can figure it out.

 

Can anyone give me any ideas?

ryank1 Enthusiast

ryank1

Posted
Posted
About 6 months ago, I would take off and my driveshaft would spin but the truck wouldn't move. And then after a few seconds, it would lock in and really jerk forward. I recently changed the rear end oil hoping that would solve it.

 

Well, it helped until yesterday.

 

I was cruising on the highway 65-70 mph and had to slow down for a traffic light. I came to a stop at the light, but there was this horrible loud noise and I think it was my driveshaft still spinning, eventhough I was stopped. It did this for about 5 seconds, and then all of a sudden the rear end locked in and made a loud noise and jerk and I initially thought the car behind me tapped me.

 

A little later, I was in the median turning left and I hit the gas but the shaft just spun again and then it locked in after about 2 seconds and jerked me forward.

 

I'm fixing to take it in to the dealer and see if they can figure it out.

 

Can anyone give me any ideas?

Sounds like you broke the spider gears in the rear diff.

concours Enthusiast

concours

Posted
Posted
About 6 months ago, I would take off and my driveshaft would spin but the truck wouldn't move. And then after a few seconds, it would lock in and really jerk forward. I recently changed the rear end oil hoping that would solve it.

 

Well, it helped until yesterday.

 

I was cruising on the highway 65-70 mph and had to slow down for a traffic light. I came to a stop at the light, but there was this horrible loud noise and I think it was my driveshaft still spinning, eventhough I was stopped. It did this for about 5 seconds, and then all of a sudden the rear end locked in and made a loud noise and jerk and I initially thought the car behind me tapped me.

 

A little later, I was in the median turning left and I hit the gas but the shaft just spun again and then it locked in after about 2 seconds and jerked me forward.

 

I'm fixing to take it in to the dealer and see if they can figure it out.

 

Can anyone give me any ideas?

 

 

Why take it in? Keep driving it... it moves sometimes doesn't it? Loud banging noises? Fresh oil will always cure that. But seriously, hang on to your skivvies, this will cost real money.

DirtyDave Enthusiast

DirtyDave

Posted
Posted

You lost the teeth on at least one spider gear. Buy a Powertrax Lock-Right and be done with it. It's a cheap solution to an expensive (over $1000 at the dealer) problem.

mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted
About 6 months ago, I would take off and my driveshaft would spin but the truck wouldn't move. And then after a few seconds, it would lock in and really jerk forward. I recently changed the rear end oil hoping that would solve it.

 

Well, it helped until yesterday.

 

I was cruising on the highway 65-70 mph and had to slow down for a traffic light. I came to a stop at the light, but there was this horrible loud noise and I think it was my driveshaft still spinning, eventhough I was stopped. It did this for about 5 seconds, and then all of a sudden the rear end locked in and made a loud noise and jerk and I initially thought the car behind me tapped me.

 

A little later, I was in the median turning left and I hit the gas but the shaft just spun again and then it locked in after about 2 seconds and jerked me forward.

 

I'm fixing to take it in to the dealer and see if they can figure it out.

 

Can anyone give me any ideas?

At first I thought you must be kind of dense because if my truck did that the first time, I'd be taking off the rear diff cover...then I thought about it some and realized you must have done that but didn't tell us what you saw inside.

 

So how'd it look in there?

 

No obvious damage?

 

Other than the issues you described, any other noises, like a whine or grind during normal use?

 

Any rough treatment that might have busted something?

ChevyHDGert Enthusiast

ChevyHDGert

Posted
  • Author
Posted

Most people have said the rear end knocking or momentarily slipping is somewhat normal for these trucks.

 

If it were a broken gears, wouldn't I feel jerking or hear grinding more often than once a week?

 

Could it be a tranny problem, like maybe the torque converter?

ChevyHDGert Enthusiast

ChevyHDGert

Posted
  • Author
Posted

Ok, maybe I shouldn't have said the driveshaft was spinning cuz that was an assumption but something was making a horrible noise for about 4 seconds and then something in the rear locked up and made the truck jerk forward as if someone hit me from behind.

 

The dealer drove it and couldn't feel or hear anything. Well no sh!t, I told them that it doesn't do this but maybe once a week.

 

Most mechanics I've talked to say if it were broken gears, you would feel it and hear it more often. They mentioned some kind of plates in the posi-trac that aren't working right and that I should try to change the rear oil again with oil from the dealer and add an additive called E-oil or something like that.

mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted

Yeah, that's what I would do. Especially if you didn't use the dealer-sourced additive. Whenever I changed my rear diff lube on a G80 in the past, I went to the dealer first and got a bottle of the additive.

ChevyHDGert Enthusiast

ChevyHDGert

Posted
  • Author
Posted

Update...

 

I was driving my truck in town and was going about 20 mph and was giving it more gas, the engine was revving but the truck wasn't accelerating so I turned around and headed straight for the dealer. As I was driving to the dealer, I could hear a grinding noise underneath the cab area so I thought tranny.

 

The dealer ran the scan tool and found no codes, he checked the tranny oil and he thought it smelled kind of funny. We drove it but of course it didn't act like it did when I drove it there. But they are thinking it is maybe the transfer case pump and my dad just told me that he thinks those transfer case pumps have like a timing chain in them and the grinding noise did kind of sound like a chain. I'm taking it back to the dealer Monday cuz they couldn't get to it this afternoon. I just drove it to work and it grinded almost all the way here (about 3 miles in town driving).

 

Does it sound like the transfer case pump?

srlbotanical Enthusiast

srlbotanical

Posted
Posted

My guess is transmission... Do you have an extended warranty? If not, I would avoid the dealer and find a good shop mechanic. Unless you have the warranty, the dealer is going to be the most expensive route you can take.

 

Steve

ChevyHDGert Enthusiast

ChevyHDGert

Posted
  • Author
Posted

Update....forget the part where I said the driveshaft was spinning cuz I don't know that for sure, it must've been something in the transfer case spinning that I heard.

 

Driving home from work Friday, my truck quit on me 3 times but I was able to make it home. Then Saturday morning as I was taking it in to the dealer, it gave out for good and had to be towed in.

 

You can give it gas and the engine will rev but the truck won't go forward and I can hear a noise under the cab. It almost sounds like a loose chain that is just rattling inside a housing, so if the transfer case is chain driven, then that could be it.

ChevyHDGert Enthusiast

ChevyHDGert

Posted
  • Author
Posted

Update...

 

Dealer called and found bits of metal in the transmission pan and recommends replacing tranny for $3400 with 3 year warranty or repairing it for an estimated $2400 with 1 year warranty.

 

Ridiculous...I'm calling Chevrolet customer service to tell them that there is no way a transmission goes out with only 49,000 miles on it.

fvisions Enthusiast

fvisions

Posted
Posted
Most people have said the rear end knocking or momentarily slipping is somewhat normal for these trucks.

 

If it were a broken gears, wouldn't I feel jerking or hear grinding more often than once a week?

 

Could it be a tranny problem, like maybe the torque converter?

 

There is no way that is a tranny problem. Open the rear diff cover and there in will be your issue. One other thing, just in case remove the fill plug if you have one first. You never know when it will be frozen up and it's hard putting oil in after the fact if the plug is jammed-up.

svensk Senior Enthusiast

svensk

Posted
Posted
Most people have said the rear end knocking or momentarily slipping is somewhat normal for these trucks.

 

If it were a broken gears, wouldn't I feel jerking or hear grinding more often than once a week?

 

Could it be a tranny problem, like maybe the torque converter?

 

There is no way that is a tranny problem. Open the rear diff cover and there in will be your issue. One other thing, just in case remove the fill plug if you have one first. You never know when it will be frozen up and it's hard putting oil in after the fact if the plug is jammed-up.

 

He just said his tranny grenaded and had to be towed lol...

mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted

Too bad you didn't try 4wd before giving it to the dealer. If it's your transfer case, you'll be spending another couple hundred on that too, after they replace the trans and the problem is still there.

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