G80 gov loc blew up

[Mudslutk51984]

My g80 (grenadie) blew in my rear of my k5.. I’m looking for another rear end but am nervous about it happening again so I was thinking about removing the gov lock out of one from the junk yard.. I been reading up and it sounds like the 10 bolt 8”5 rears are the worst but the 3/4-1 ton g80’s do good.. any info or advice??

 

[mechted]

Answer these questions:
What size tires are you running now?
What size tires do you want to be running?
What kind of offroading do you like to do?
What gears are in it now?

If you just need to get back on the road: a replacement G80/open carrier from the same axle is the best bet. Drop it in and go. Provided your gearset didnt take any damage. If the gears are trashed, replacement of the whole axle is probably easiest.

Changing from 1/2 to 3/4 ton means likely changing the wheels to 8 lug. Unless you can find a 6 lug 14 bolt semi floater. 3/4 or 1 ton gear is far more reliable for larger tires and offroad conditions.

You will likely have to re-gear either the rear to match the front or the front to match the rear... unless you can find a matching axle. If you do go this route: go for the gearset you should have, based on the tire size you want, not the gearset you do have right now.

If you are looking at full rear end replacement, look at newer trucks (2000+) for factory disk breaks with integrated parking brakes in the hat of the rotor. This will likely require moving spring perches and shock mounts (welding) but is relatively easy. Sticking with drum brakes in the rear is tried and true and no problems. Disks will give slightly better braking but require a fair amount of work to get it working correct.

 

[Mudslutk51984]

Answer these questions:
What size tires are you running now?
What size tires do you want to be running?
What kind of offroading do you like to do?
What gears are in it now?

If you just need to get back on the road: a replacement G80/open carrier from the same axle is the best bet. Drop it in and go. Provided your gearset didnt take any damage. If the gears are trashed, replacement of the whole axle is probably easiest.

Changing from 1/2 to 3/4 ton means likely changing the wheels to 8 lug. Unless you can find a 6 lug 14 bolt semi floater. 3/4 or 1 ton gear is far more reliable for larger tires and offroad conditions.

You will likely have to re-gear either the rear to match the front or the front to match the rear... unless you can find a matching axle. If you do go this route: go for the gearset you should have, based on the tire size you want, not the gearset you do have right now.

If you are looking at full rear end replacement, look at newer trucks (2000+) for factory disk breaks with integrated parking brakes in the hat of the rotor. This will likely require moving spring perches and shock mounts (welding) but is relatively easy. Sticking with drum brakes in the rear is tried and true and no problems. Disks will give slightly better braking but require a fair amount of work to get it working correct.

I have 35” tires, and occasionally go play around in the mud not as much as I used to, a lot of slippery winter driving, the ring and pinion are unscathed, and I have 3.73 ratios. I found some tight rear differential at the junkyard but it turned me away because the perches were farther apart on a 1995 Tahoe.. any advice on getting differentials from gmt400’s?

 

[diesel4me]

Around here I've seen more of the GMT400 1/2 ton trucks diffs fail,than probably any others,finding a good salvage yard one is usually a challenge and they are expensive if you do find a good one..
Your area may vary.
It may be more of the later ones suffered from rust holes in the diff cover letting the lube escape,or were overloaded constantly, than them just being "junk",but I see quite a few GMT400 trucks with blown rear diffs for sale ,and my friend has replaced a dozen or so at his shop in the past year or so..

I'd say its worth getting a 14 bolt and having the perches moved in the long run..

 

[mechted]

35's typically mean go 3/4 ton if you want it to last through offroad abuse. Ideal replacement would be a 6 lug 14bsf from late 80's/early 90's era truck. But those can be difficult to find.

3.73 should be a fairly common ratio. Not that hard to find in any axle you end up going with. Ideal ratio for 35's tend to be higher though. A lot are happy at 4.56 when they have overdrive. 4.10 is also very common.

As for moving the perches from a 95 axle to match what you have, its not uncommon. Cut off the old stuff, clean up the tubes, use replacement perches and shock mounts:
https://www.ruffstuffspecialties.com/catalog/springperchantiwrap.html
http://diy4x.com/product.php?productid=17755&cat=250&page=4

If you have access to a welder, assemble the whole thing, vehicle weight on the axle/tires, set the pinion angle, then tack weld in the perches. Disassemble to get access, then burn it in solid. A small 110v welder can do the tacking, then disassemble and take it to a shop if you have to. Or look into mobile welding services.

 

[dyeager535]

I second at least the 14sf in your application, and I wouldnt consider you a real good candidate for a G80 due to the mud, unless you are fine with an open diff in those conditions.

 

[Mudslutk51984]

I’d like to change the ratio but that’ll have to wait. Just have to get it on the road again.. I found a carrier online for $100. I don’t want open and I don’t want the g80 again out of nervousness of locking it up again the highway. So I was going to see if I could find a lsd carrier because that would be my happy medium .. how much better are the lsd compared to open carriers?

 

[Bent77]

Well they are good except you will need to reset the pattern/gears/bearings to do it, and you still have a 10b

I have a 14BSF I pulled out of a GMT400 truck. $100
Using an ARB in it. 3 years now, but fingers still crossed...

 

[dyeager535]

I’d like to change the ratio but that’ll have to wait. Just have to get it on the road again.. I found a carrier online for $100. I don’t want open and I don’t want the g80 again out of nervousness of locking it up again the highway. So I was going to see if I could find a lsd carrier because that would be my happy medium .. how much better are the lsd compared to open carriers?

14SF G80's hold up pretty well. I've seen damaged ones, but thus far it appears the carriers can take a failure of the locking mechanism, where the 10 bolts can't. That's the rub with the G80...it's more likely to have problems than an open diff or locked rear, but its also seamless in operation, and provides superior traction in conditions MOST people need it to.

I don't consider LSD's an option in trucks. Trucks weigh far more than cars, and are more often in situations where a majority of weight is on one wheel. LSD's will slip under those conditions. The closest I'd consider in a truck to an LSD is the Detroit Truetrac, but under the right conditions (one wheel with zero traction, such as up in the air, also probably one wheel on ice) those too "revert" to open differential performance.

From all I've read of people who run mud, a true locker of some sort is necessary. Air locker, e-locker (I see Eaton now has a rear diff that operates basically like an automatic transmission to lock up), standard locker, or even a spool.

I'd dump zero dollars into ANY 10 or 12 bolt if I was doing anything other than using your truck to get to the mall, and drove it like an 80 year old near blind person at night. I enjoy accelerating and I don't like worrying about the rear end (having destroyed a 10 bolt G80 on the street with 33's), the 14SF IMO is a happy medium that keeps you from worrying about most failures, without the expense, weight, wheels, and clearance you would lose with a 14FF. The 14FF strength-wise is a superior axle assembly, just unnecessary IMO from what you describe. The 14SF would have a pretty significant "safety" margin from what you describe your driving habits to be, and tire size.

Note: The OPEN carrier 10/12 bolts seem to hold up fine, but an open diff isn't comparable in traction. If you need a real traction aid (not LSD) I would consider the 10/12 bolts iffy enough to as not spend the money on them.

 

[6872xtc]

If you only replace the carrier, and reuse the same ring gear, just check your backlash and set it to the same or slightly tighter. I wouldn't worry about the gear pattern if you aren't doing anything with the pinion.

I had a 10 bolt drop a tooth off of the pinion, but the G80 was fine. It had 236K on it when I put it under my truck, and it went another 6K or so, even went wheeling in Moab, then took a poop on the street. So I wouldn't hesitate to put the 10B back together and just plan for what you want in the future.
I have a 12B under my '70 with a big block, and even with 4:56 gears, I haven't killed it with wheeling or burn-outs. It had 33s for a long time, now 35s. But I also like the 6 lug SF 14 bolt that I had under my '90 Jimmy for a while. I got it out of a '92 IFS truck, so it took a little bit of work to install, but it was a nice upgrade in my opinion.
Too bad that you aren't close to me, I have scrapped several 10 bolts which had good open and G80 carriers and there are more around in this area.

 

[diesel4me]

I've been lucky with some 10 bolt GM diffs..the 4:10 open carrier one in my GTO saw daily burnouts for years without any troubles at all--the light weight of the car and being non-posi probably was why,but I used to smoke the tires off it going around rotary circles in second gear till the tires nearly popped so many times in that car I was very surprised--the TH400 in that car held up to a ton of abuse too..

I buried the car in a snowy field once and sat there rocking it from drive to reverse a good half hour until it finally get free--I smelled something like burning brake shoes by then,the next morning when I started the car,it sounded like a siren for 5 minutes,then it slowly died down..when I put it in gear,it kind of "slid" on,not a firm "Thump" like usual--I drove it to a mechanic I knew from work,he put a new filter in the transmission --when he pulled the pan off,it was full of coffee grounds looking pieces,he went "eeeww--this aint good!"..

He asked if I wanted him to just keep going and yank it out--I said no,I need to get to work this week"--so he just put the new filter in,I filled it back up--to my surprise it was silent now,and still roasted the tires,I drove it two more years without a failure!..

All my 1/2 tom GM 4x4s had their original 10 or 12 bolt rear diffs,I never broke one,I admit I didn't whale on them off road and they were not powerful enough to do smoke shows,but plowing puts some load on them--as long as your not whaling the tar out of them or shock loading them off jumps,they do OK for their intended street use..
I don't think any of them had a posi though,or a gov loc..

 

[dyeager535]

Yeah, the open carriers seem to hold up much better. Just not beefy enough to handle the shock load of the gov lock over the life of the diff apparently, especially as we add more tire weight and power.

The one I broke obviously had lasted from factory without issue for over 10 years.