Rear End Won't Lock

[mcbockalds]

My 2007 classic 4.8L 2 wheel drive work truck 1500 Silverado auto trans with a locking rear differential that has worked fine in the past did not work at all yesterday in our snow storm. It didn't work in reverse or drive on probably 10 or more trys as I struggled to get out of the driveway and down the alley in 12 inches of snow. Also only the right rear wheel had power, never the left. 92,000 miles on the truck with way more than half of those on the highway (this truck has had an easy life!) Any thoughts?

 

Cheers John

[MikeInCtown]

I notice that mine will not lock if I have the traction control on. I need to have more power applied. I found this out while struggling to get up a highway entrance ramp in a snowstorm once. the truck kept wanting to ride further and further to the right and I almost got into the wall. Turned off the TC and it went straight and took off.

[oldmann]

Could be time for an oil change.

[mcbockalds]

I notice that mine will not lock if I have the traction control on. I need to have more power applied. I found this out while struggling to get up a highway entrance ramp in a snowstorm once. the truck kept wanting to ride further and further to the right and I almost got into the wall. Turned off the TC and it went straight and took off.

I don't have traction control though, but thanks.

[mcbockalds]

Could be time for an oil change.

Can that actually be the problem? Or just a thought?

[MikeInCtown]

I think he meant gear oil. the recommended service interval is 100,000 miles on the rear IIRC. I know I had to change mine when I got my truck at 100k. Also know that GM recommends the additive for limited slip differentials if the oil doesn't already have it in there. For example, most gear oil doesn't have the additive, but some products like the one I got from Red Line specifically said on the label that it has the additives for limited slip differentials.

 

This was 4 1/2 year back so product labeling or formulas may have changed, but the factory recommendations likely have not.

[Bob D]

...Also know that GM recommends the additive for limited slip differentials if the oil doesn't already have it in there....

 

Locking rear is not limited slip.

"The use of any additive in locking rear axles (G80)

is not recommended. Rear axle additives are designed for use in limited

slip differentials which are normally installed in cars. All light duty

trucks equipped with RPO G80 make use of a locking differential and the

use of additives will delay the engagement of the locking mechanism and

may decrease axle life"

[Badass69]

Its a gov lock in a 10 bolt... its probably dead. The little teeth on the gear and knocking plate like to strip leaving you with a permanent open diff

 

 

Sent from the Great White North

[mcbockalds]

So today it started locking up when called for. Who knows what is going on? I will change the fluid and see what happens. Thanks for all the replies.

Cheers John

[Badass69]

Change the fluid and take a look at the lock plate. Its probably missing teeth. Use fluid with no friction modifier.

 

 

Sent from the Great White North