Locking Rear Diff?

[Calgary GMC]

I believe the term used by GM is a "Locking Rear Differential". Is this just another name for a Limited Slip diff? Or, it the rear diff in my truck truly a locking diff (i.e. both wheels lock together)? How does the locking mechanism work?

 

Thanks!

[lrymal]

Go here, it will get you in the right direction as to what is what. Takes a bit of reading (the URL), but after you go through it, you will know all you need to know:

 

http://www.gm-trucks.com/forums/index.php?...ndpost&p=349732

[Calgary GMC]

Go here, it will get you in the right direction as to what is what. Takes a bit of reading (the URL), but after you go through it, you will know all you need to know:

 

http://www.gm-trucks.com/forums/index.php?...ndpost&p=349732

 

<{POST_SNAPBACK}>

 

 

 

Thanks very much, that's great information.

 

That does bring up another question though. When I've had my truck in the Auto 4wd mode, I can feel it was taking a split second or so of slippage for the transfer case to engage into 4wd mode. Is this really the case, or might it be the locker engaging instead?

 

I've had Jeeps (i.e. Cherokee and Liberty) with the Selec-trac 4wd (full-time 4wd) system, and its engagement was always seemeless. I could never tell when it was engaging or dis-engaging. Hence, either the GM Auto 4wd system isn't as refinded, or this is actually the locker engaging that I feel upon slippage not the t-case?

 

Thoughts?

[fossil]

Mines the same. It's just not as refined, nothing to do with the locking diff.

[lrymal]

...I've had Jeeps (i.e. Cherokee and Liberty) with the Selec-trac 4wd (full-time 4wd) system, and its engagement was always seemeless.  I could never tell when it was engaging or dis-engaging.  Hence, either the GM Auto 4wd system isn't as refinded, or this is actually the locker engaging that I feel upon slippage not the t-case?

 

<{POST_SNAPBACK}>

 

 

The Silverado SS uses a full-time system as well.

 

My understanding is that the setup in these Z71 4WD is such that a bit more fuel mileage can be had with its setup since there is not as much drag while in AUTO 4WD mode. Otherwise, they would have used the SS's method.

 

This could be as wrong as can be, but I think that is the reason.

[mmmikkke]

It's not a matter of refinement, it's a matter of efficiency.

 

The GM system has to detect wheel slip before it engages 4wd. That's the delay you feel.

 

The lighter-duty mopar system uses a viscous coupling and so it's able to transmit power immediately. But it's also able to waste power continuously.

 

Which would you rather have...a 1-sec delay when in "auto" mode, or the mopar approach with it's inherently poorer fuel economy?

 

Personally, I'd rather have neither. I prefer manual 4wd control. I can tell when I need it, and I know when to disengage it. I had the GM "auto" mode on my 2002 Z71. I tried it a few times, decided it was drivers who are more detached from their vehicles that I was, so I never used it after that. Instead I just used 2wd or 4wd explicitly.

 

When I bought my 2005 2500HD, I opted for the floor mounted manual transfer case control, which was only available in the Chevy, not the GMC. It permits much faster mode changes and is better suited for the thinking driver. Pull the lever, and 4wd is engaged, push it back and it's disenagaged. No waiting for the flashing lights on the 2wd and 4wd buttons on the dash.