Clunk in my rear axle..Gov-Loc??...

[diesel4me]

While fooling with my '85 Suburban,driving it in my yard,I noticed a clunking in the rear axle and it feels like someone is kicking the rear quarter when it clunks,the truck jerks sideways a bit too..I'm hoping its not a serious dilema,as I have sunk more $$$$ into this thing than I should have already (having buyers regret in ways,as I find more "issues" with it daily!)..

Its snowing now, and I didn't think to count the cover bolts while I was under it yesterday,it could be a 10 bolt or a 14 bolt 6 lug SF axle..I'm hoping its not a worn diff case or side gear if its a 10 bolt,I know those were common to fail..how would I tell if it has a Gov-Loc,any way to tell without pulling the cover ??..I have the options list in the glove box,is there a certain code it would be listed under??..any info would be appreciated..

 

[BLIDVL]

G80 is the RPO code for a Gov loc, least it is on my Sub.

 

[corelokt]

Two things.
I have a gov lok, acts as you describe.
My dads truck, bone stock 1/2 ton 2wd also does what you describe with over 200,000 miles on it. It has been doing so for about 100,000 of those miles. Old and worn doesn't mean it will become old and broken. If your like me and every little odd sound or quirk irritates the bejeesers out of you, pull the cover with the rear end up the air. Check the drive line for slop.

 

[diesel4me]

I dont mind "noises" as long as I know they aren't a genade waiting to go off!..the rear end seems pretty "tight" when shifting from drive to reverse,there isn't a ton of bacvklash or any clanging going on then,its just while cornering at low speeds,I definately sounds like a posi locking and unlocking..my bet is it has a gov-loc,I was just thinking maybe it wouldn't be a bad idea to pull the cover before I go to put this on the road and ensure nothing in it is flopping around I could fix (or fudge!),
BEFORE I have a real problem,hate to have something go through the ring and pinion,ya know?..if I find it is a gov-loc and its about to grenade,is there a way to "gut" it and malke it a "normal" non-posi??..
on the other hand,maybe if it looks OK inside, a refill with new gear lube and some posi anti-chatter additive might help--I dont mind turning the radio up and ignoring noises if they are not going to be a big deal,!!..if it gets above 32 and the wind blows less than 40 mph,maybe I'll get to LOOK at it before spring!.

 

[onetonbb74]

use regular gl4(80w90) in your g-80 gov lock, if you use gl5(posi additive), it will cause the pins to stick causing the gov loc to not work properly and possibly jam either locked or unlocked...

 

[Teck]

They are known for the carrier braking when they get old. Mine was broke and still driving when I took it out for a 14FF. I could not believe it was still going in the shape it was in.

 

[diesel4me]

Well,I looked at the codes in the glove box tag,and it IS a "G80" code! ---but its also a TWELVE bolt!..(I counted them 4 times!)...it appears to be the original rear end too,nothing looked "newer" ,like the u-bolts,or any less rusty than the rest of the truck,it appears unmolested!...I thought GM only used 12 bolts till 1980 or so??..

did 12 bolts have gov-locs too??...maybe I got an older rear end with a detroit locker in it or something,I wont know till I can yank the cover off--that might be spring!..

 

[scouthead]

My Blazer did the same thing for a couple months...

Then the gov lock exploded.

 

[Never Satisfied]

My Blazer did the same thing for a couple months...

Then the gov lock exploded.

Sounds eerily familiar...

 

[AJMBLAZER]

Well,I looked at the codes in the glove box tag,and it IS a "G80" code! ---but its also a TWELVE bolt!..(I counted them 4 times!)...it appears to be the original rear end too,nothing looked "newer" ,like the u-bolts,or any less rusty than the rest of the truck,it appears unmolested!...I thought GM only used 12 bolts till 1980 or so??..

did 12 bolts have gov-locs too??...maybe I got an older rear end with a detroit locker in it or something,I wont know till I can yank the cover off--that might be spring!..

Sounds to me like someone swapped a 12 bolt in a long time ago. GM had used up their 12 bolt stock pile long before 1985.

Yes, 12 bolts got Gov-Lock's.
Mine does something similar...now you all are making me nervous. Every now and then when I go around a curve or start coasting it will make a clunk.

 

[owenst7]

With a 14bff, you can gut the G80 components and it will function just like the open carriers with one less spider gear (probably a bit weaker).

Never looked at a 12 bolt G80. Worst case is you could probably get an open 12 bolt carrier cheap/free. Unfortunately you'd probably have to re-shim everything and properly set up the gears.

Although you've already discovered if it is a G80, for anyone reference:
I think the G80 is tuned to kick in somewhere around 100 rpm difference between wheels (correct me if I'm wrong). I noticed on mine that if you spun the tires in different directions, it was pretty easy to get it to lock up. Just spinning one tire by hand was difficult to get it going fast enough without a wheel mounted.

These things were a pretty good design, they just had way too loose of tolerances. All the slop they had coupled with fully locking abruptly at such a high wheel speed put way too much shock loading on the wimpy components. I don't know how GM thought they were appropriate. The ones I've fiddled with were all stripping teeth even in stock trucks with pretty weak motors and street tires.