Used Gears, What to look for?

[Stephen Carter]

So, since the debacle with the rear on my K5 NOT being a 3.42 like the RPO codes calls for, I'm trying to at least get the 4x4 working with a set of used gears.
My question is, when I go to the pick n pull, what should I be looking for?
I have not opened the cover on the axle yet to confirm 3.08 gears, but assuming 3.08 gears do I just need to pull the ring and pinion or would it be best to use the carrier the gears came on?

Thanks for any advice!

 

[Blue85]

10-bolt carrier break is silly low, so anything you might run in a truck will be OK on the stock carrier, so a carrier swap is only needed if you want a different differential. In other words, does it have a gov-lock now? This would be the time to do a locker if that's in the plans. Finding 3.08 gears should be super easy. You can probably even find complete 3.08 axles for free and the axle swap might be simpler than a gear set-up. But why 3.08? Why not move to a real ratio if you're putting work into it? Sounds like you have one axle at 3.08 and one at 3.42 (?). Why not go 3.42 at both ends or even 3.73? What size tires do you have?

Oh yeah, the original question is what to look for. The first thing is broken teeth, which means the set is junk. Don't try to mix a ring and pinion from two sets - keep them together. Next is rust. Minor surface rust that cleans up with a wire wheel is fine. Minor pitting is OK, but when any significant portion of the contact area is pitted, just say no. Especially with something like 3.08 that everybody is throwing away.

 

[Stephen Carter]

Well I'm on the hunt for 3.42, which is what my rpo list calls for.

The truck currently sits on 35s, and a 6" lift, In the future I'd like to do 4.10s or 4.56s, but at the moment, having a crappy job does not allow for spending 600 in parts for my 'toy/get to work in the snow' vehicle.

:edit: i don't know if it has the govlock in it or not, when spinning the rear wheels, one goes forward, the other backwards, but I believe an open diff does that as well as the g80.

 

[Blue85]

There's a 4.56 axle in the classified section right now for $100. You might spend that much on a gear set, not to mention an install kit. Do you know how to set up gears? A shop will charge a few hundred at least...

Why spend any money on 3.42 when it doesn't work right with 35's anyway? Have you priced a transmission rebuild?

 

[Stephen Carter]

There's a 4.56 axle in the classified section right now for $100. You might spend that much on a gear set, not to mention an install kit. Do you know how to set up gears? A shop will charge a few hundred at least...

Why spend any money on 3.42 when it doesn't work right with 35's anyway? Have you priced a transmission rebuild?

I know the basics of setting up gears (technical minded, it seems simple, but time consuming).
The end game is just to get it running, so I can use 4x4 if I need to, because as it sits, its a fancy lifted 4x4 that is best suited as a yard ornament. At this point, if I have to regear both ends, it'll get sold, and I'll find something that doesn't need to be regeared.
I know that spinning 35s with the wrong gears can and will eventually cause the trans to give up the ghost, but in this area, a rebuild is ~400-500 from what I've seen. It probably already needs a rebuild, as I have zero clue as to how long it was driven with the 3.08s.

I do plan on getting a large trans cooler to help, and I'm on the hunt for a better job at the moment, so who knows, in a few weeks, this question could be moot.

 

[jeff in co]

I'd keep it simple. Just find a complete axle with 3.42's in it. Much easier and probably cheaper than trying to install new gears.

If you're going to Pick n Pull, they probably have to have something out there that can work. My local place charges $100/axle. That's going to be much better (in my opinion) to get you back on the road.

 

[sweetk30]

crazy question . . . .have you even checked the front diff to make sure you get the ratio for the rear ?

if its not stock to the rpo code then who knows if the front is original even .

 

[paratrooper307]

crazy question . . . .have you even checked the front diff to make sure you get the ratio for the rear ?

if its not stock to the rpo code then who knows if the front is original even .

This. It's always worth taking 10 minutes to pop off the diff cover and see what you're actually working with on these trucks. I can feel the pain of needing to get something running, although as others have said, 3.42s or 3.73s with 35s won't make your transmission happy. You may be able to swap your 35s with someone for a more axle-friendly size. I second the recommendation of getting a complete axle-less time to set up, fewer things to go wrong-plus you can unload the existing axle for scrap, on Craigslist, or keep for spare parts.

 

[Blue85]

Same thing goes for looking at used axles. Never take somebody's word for what ratio it is, what differential it is or what kind of condition it's in. It's not that people are generally liars, they just have the wrong information pretty often. Before you even drive to look at an axle, get pictures of the insides. You'd be surprised how many axles are sitting around that were "working great when pulled" that have chipped teeth or are all rusty inside.

 

[campfire]

crazy question . . . .have you even checked the front diff to make sure you get the ratio for the rear ?

if its not stock to the rpo code then who knows if the front is original even .

This. Someone has obviously changed things, bets are off on the front.

Have you been using 4WD so far? You would have quickly figured out if your gear ratios were off by that much.

 

[Stephen Carter]

This. Someone has obviously changed things, bets are off on the front.

Have you been using 4WD so far? You would have quickly figured out if your gear ratios were off by that much.

Sorry for the late reply. Been dealing with job crap.

No. I have not been using 4wd up until I tried it the first time when I found a front driveshaft.
I realized that something was off when just going the 50' down the driveway it felt like i was pushing/pulling something. Lifted the truck, spun wheels and watched the pinions move, the front spun more times than the rear. Which is strange cause this thing actually gets up and hauls ass.

I've yet to actually pull covers and carriers and count teeth.

At this point, I've been thinking about how to do an axle swap, and I've come to the realization I do not have the support available for lifting/supporting a lifted vehicle. So I've decided I'm just going to save and buy 4.56s and put them in.

Just as verification, the are both 10bolts with the 8.*" carriers correct?

 

[campfire]

Yes, both are 10-bolts with 8.5" carriers. Why bother redoing both of them? Are you wanting 4.56 gears anyways?

 

[Stephen Carter]

Yes, both are 10-bolts with 8.5" carriers. Why bother redoing both of them? Are you wanting 4.56 gears anyways?

The original plan was the roll the 3.42s til i could afford 4.56s as according to my math, 4.11s with 35s, buts me back at 'stock ratio'. and 4.56s puts me a little over, so I may cruise at a higher RPM, but it may give the trans a bit of relief.
But with different ratios, that plan got shot all to hell...

I've thought about getting some lockers as well for both axles, a long time ago when i was into drag racing, there was a company that supplied a few parts to change from an open diff to a locker by replacing the spider gears. anything like this still exist?

 

[campfire]

The original plan was the roll the 3.42s til i could afford 4.56s as according to my math, 4.11s with 35s, buts me back at 'stock ratio'. and 4.56s puts me a little over, so I may cruise at a higher RPM, but it may give the trans a bit of relief.
But with different ratios, that plan got shot all to hell...

I've thought about getting some lockers as well for both axles, a long time ago when i was into drag racing, there was a company that supplied a few parts to change from an open diff to a locker by replacing the spider gears. anything like this still exist?

There are a number of such drop-in "lunch-box style" lockers, but I'm not sure what such options exist for the 8.5" axle. You can replace your spider gears with a solid bar which will be locked all the time (mini-spool), but I'm not sure what other lunchbox options are available for this axle. It's not hard to break 10-bolt axle shafts with low gears, lockers, and large tires. Consider that before dumping hundreds of dollars into gearing, lockers, and tires.

Pushing front wheels around is also more difficult if the front axle is locked, so a lot of guys wind up reinforcing and upgrading the steering system significantly after a few trips with a locked front that doesn't want to steer anymore. You have been warned.

 

[campfire]

Also, check both axles axle before buying any parts. If you have the G80 "Gov-Lock" option the carrier is different and lunchbox lockers won't work anyway. It's also worth noting that 8.5" G80 carriers have a fairly high failure rate, even without any offroading abuse.

 

[Stephen Carter]

Also, check both axles axle before buying any parts. If you have the G80 "Gov-Lock" option the carrier is different and lunchbox lockers won't work anyway. It's also worth noting that 8.5" G80 carriers have a fairly high failure rate, even without any offroading abuse.

Of this I am aware lol. I know they are called gov-bombs for a reason. It would surprise me if it was a G80 still.