Chevy & GMC Vans

Hi guys, long since been advised 4.10 or 4.11 diff ratios are the ones to go with when running 31 inch tires on my 98 AWD, so time to see what's what!
The front appears easy found these on Amazon
Yukon (YG GM7.2-411R)
Then at the rear there is quite an array to choose from (different makes) and just wondering what will fit as I have the G80 LSD! So thinking 'keep it in the family' found these
Yukon (YG GM7.5-411)
Good choices or bad? Anybody care to enlighten me as to a better combo or indeed tell me the the advantage of 'thick' crown wheels if any.
Many thanks
Shep

astroshepawd wrote:Hi guys, long since been advised 4.10 or 4.11 diff ratios are the ones to go with when running 31 inch tires on my 98 AWD, so time to see what's what!
The front appears easy found these on Amazon
Yukon (YG GM7.2-411R)
Then at the rear there is quite an array to choose from (different makes) and just wondering what will fit as I have the G80 LSD! So thinking 'keep it in the family' found these
Yukon (YG GM7.5-411)
Good choices or bad? Anybody care to enlighten me as to a better combo or indeed tell me the the advantage of 'thick' crown wheels if any.
Many thanks
Shep

There should be OEM gears available in that ratio too. I'm 90% certain that's what's going into my van next week (don't have the write-up right in front of me). My gear guy indicated they'd be the quietest for on-road use, even though they may cost a bit more.

Hi Everyone,

This is getting super exciting
I too would like to re gear to 4.11 for my 2003 AWD .
I am tempted to get the Cooper tires first, Discovery LT215/85-16 which is nominal 30" OD.
I have 3.42 diff ratio now with open diff on rear.

I drive my van slow and it is not daily driver. Maybe I can wait on the diff ratio. When I go on dirt trails I like to go slow in 4 low range of my cable shifted np231c t case. So in low range the taller tire should not be a problem.

AP

AP, I've driven like 5 years on my 245/70-16 (nominally 29.7") Geolandars with 3.42 gears. You can do it, just beware of short Highway on-ramps, and know that climbing mountains is going to suck.

For mountain roads, holding the tranny to 3rd is the bare minimum for me, but even then I get a lot of hunting between 2nd/and 3rd because everything's too tall.

Thanks for the reply Herbie, cost is a factor for me and I would also like to collect if possible from the Everett branch/factory!
Two of these (front & rear) would cost a fortune back to the UK let alone the tax on top!
So after you say OEM is quietest OTR, is that true? Anybody?
Anybody running Yukon gear in their van?
Thanks
Shep

astroshepawd wrote: Anybody running Yukon gear in their van?

Yes.

Hi Everyone,

Hi Herbie, Good to hear that 3.42 ratios can been ok for 245/70-16 Geolanders.'

My 2003 AWD has 3.42 axles.

Now I am thinking of Cooper Discover AT/3. LT245/75-16. Load range C. 41 lbs, 30.3" nominal O.D. Or even standard load P245/75-16. Cooper Discover AT3.

The LT215/85-16 are load range E which is too stiff.



AP

That's the tire and size I'm running now with 3.73 gears. Wouldn't want to run that size with 3.42!

Yeah, there's "getting away with it", and then there's "it works well".

I was getting away with it. Definitely not ideal. The van was pretty universally sluggish. With the pop top, rack, etc. my aero was even worse than normal, so I couldn't ever really drive in the power band in 4th gear, because it wanted to go like 80mph but the wind said "LOL, nope."

How're the new gears treating you?

Stroverlander wrote:How're the new gears treating you?

The gears are great. I'm still on the fence about the Lock-Rite lunchbox.

Just got back from a 2000+ mile trip up to Oregon for the "Descend on Bend" van campout, and having the gears done made *all* the difference. Lots of climbing up and down mountains, lots of passing slow trucks, etc. and none of it would have been possible on the 3.42s.

The locker... eh, I'm not sure it's working right, and I need to talk to my installer. I get the "normal" ratcheting sounds when making tight turns, and that's fine, but it also has this habit of giving some very loud bangs and making the van lurch at odd times. Like, just going down a straight paved road, I'll get two or three bangs and the van will jump to the right. On-ramps also seem to be a problem - even long ones with a gentle curve - when I'm on the power I'll get some uncomfortable lock-ups where slams things pretty hard.

Whether it's "normal" or not, I can't say yet, but I definitely don't like it. Having the locker was great when everyone around me was getting stuck in the soft high-desert silt outside Bend, OR - I just trudged through no problem, but all the bad behavior on the street definitely has me wishing there was a selectable locker available for our rig.

One thing I need to look into is the overall health of the rear axle. It had been bent at some point, and part of the labor of installing the new gears and lunchbox was that the diff shop had to straighten it. While in Oregon, I found an unattended but operational weigh station and spent some time moving on and off the pads to confirm what I suspected: my van is woefully over-weight, particularly on the rear axle. There's a chance some of what I'm experiencing is a matter of over-load on stuff back there. Damn, I really didn't want to have to build a custom heavy-duty axle...

That's great about the gearing and disappointing about the locker! Hopefully you can get some resolution from your installer on it seeing you didn't exactly get the one you wanted.

Curious what kind of weight/bias/overload you're seeing on the scale?

Stroverlander wrote:That's great about the gearing and disappointing about the locker! Hopefully you can get some resolution from your installer on it seeing you didn't exactly get the one you wanted.

Curious what kind of weight/bias/overload you're seeing on the scale?

With just driver (me), 3/4 tank of water, 3/4 tank of gas, and a normal camping load of gear, but not my wife/daughter and their stuff, I'm at 6300lbs. (2900 front, 3400 rear). That's at least 200lbs over the GVWR, and I believe 300 lbs over the rear axle rating. (I need to double-check the sticker to be sure on the GAWR).

EDIT: Oh jeez. I just realized I'm exceeding the weight rating of the rear springs, too. Guess I need those HD springs after all...

Those are interesting numbers for sure, thank you!

I just ordered and received my 22-687HD springs for around $250 shipped:

https://www.generalspringkc.com/Product ... e=22-687HD

We've fully hijacked this thread now

Yes, I think I too will need to order the HD springs. And put the van on a diet.

It should be noted that my aforementioned "normal load of camping gear" is pretty dense:

Full tool set (every tool I've ever used to work on the van, except air tools, plus a couple of items)
Full SafeJack bottle jack and compact jackstand setup
Portable Compressor
Recovery gear (straps, traction mats, shovel, lots of steel D-rings, etc.)
A pretty heavy aluminum chuckbox packed with cooking gear
A fully loaded pelican case of camera gear
5gal jerry can of fuel + 5lb bottle of propane on the rear rack
The fridge cabinet, with full fridge
Dometic Porta Potti + 40lbs of flush water
Portable Propane campfire
60W solar panel + racking (dedicated cross bars, etc.)
Group 31 house battery (100lbs of lead)
and probably 2-dozen smaller items that add up to another 100 lbs.

So yeah, it's 10lbs of crap in a 5lb bag.

Just for comparison's sake, though - my 6100lb GVWR is a full 500lbs higher than a 2017 Colorado w/ the gas engine, and only 100lbs shy of the diesel version. So the fact that I'm overweight is not a failing of the Astro.