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Discussion Starter #1
Hi I have a 1989 suburban 2500 4x4 with manual lock out front hubs. My question is, when I shift into 4x4 does that lock the front and rear axles into posi-traction?
 

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Shifting into 4wd only locks the transfer case. The differentials operate completely independently. I doubt there's any kind of traction aid in the front diff, unless you've put it there, because OEM's don't like to put traction aids up front at the factory. Rear may have a traction aid or may not. G80 is the usual RPO code to look for, but I don't know if that will refer to the Eaton Gov-Lock or a clutch type LSD in your year.
 

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Discussion Starter #3
Thanks MrShorty

I noticed while crawling under the truck that there is a cable that goes to a lever sticking off of the rear pumpkin. I thought maybe that was linked to a diff lock or something that activated when in four-wheel-drive. From your response it sounds like it is possible the rear has a locking device, but for sure the front would have an open differential?

I always thought that the rason they didn't want you to drive on dry pavement in 4x4 is becuase all the differentials are locked?

So without a traction device up front, in most slippery situation (like mud) you really end up with 3 wheel drive if one of the front wheels starts spinning since there is an open differential up front?

Also where would I find the RPO code? Is that on the rear axle?

thanks for the insight!!
 

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When you open up the glovebox, there should be a fairly large sticker there with a whole ton of incomprehensible numbers and letters. Those are your RPO codes. If you decode those RPO codes, you will find out pretty much every single option, nuance, and otherwise about the truck when it left the factory, right down to the original colors.
 

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Discussion Starter #5
Thanks Crawdaddy! Now I know what I'm going to do as soon as I get home. Find out what treasures are lurking in that $500 hunk of smoking metal! (hopefully the smoke will go away when I get the new engine in!)
 

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OK, I'm learning about my truck. I checked the RPO codes and have GQ1, GU6, G80. Does that mean I have open diff in front, 3:42 gears, Posi in the rear?

'93, 1500, Burb, 5.7, 4x4

Found a link to this website on another posting

http://www.rpocodes.com/GM-RPO-codes/gmrpocodesGthroughM.html

Researched my RPO and this it what I found

GQ1- Open Diff
GU6- 3:42 gears
G80- posi traction/locking diff
Z82- Trailering equip'd
M30- 4L60E, 4-Speed Auto
L05- v-8, 5.7, TBI
 

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OK, I'm learning about my truck. I checked the RPO codes and have GQ1, GU6, G80. Does that mean I have open diff in front, 3:42 gears, Posi in the rear?

'93, 1500, Burb, 5.7, 4x4

Found a link to this website on another posting

http://www.rpocodes.com/GM-RPO-codes/gmrpocodesGthroughM.html

Researched my RPO and this it what I found

GQ1- Open Diff
GU6- 3:42 gears
G80- posi traction/locking diff
Z82- Trailering equip'd
M30- 4L60E, 4-Speed Auto
L05- v-8, 5.7, TBI
Yes it does, providing it hasnt been swapped out over the years.
 

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Thanks RayVoy

- - - Updated - - -

Tim,

I guess I can see what happens in the snow when I get the Master Cylinder fixed. Thanks
 

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Thanks MrShorty

I noticed while crawling under the truck that there is a cable that goes to a lever sticking off of the rear pumpkin.
I believe what you saw was the brake bias lever. It adjusts the brake pressure by sensing how much the suspension compresses from a heavy load.
 

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Discussion Starter #11
I believe what you saw was the brake bias lever. It adjusts the brake pressure by sensing how much the suspension compresses from a heavy load.
Yep! I have since learned that is what it was. (no longer have the truck) I'm assuming those disappeared when ABS became standard? I haven't seen one on my 91 k2500 pick up or on later trucks.
 

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Wow, I guess I need to pay more attention. I didn't realize the OP was 5 years old.
 
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