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Is there a code in the glove box? I' trying to avoid pulling the cover or guessing by spinning the tire and counting the drive shaft ratations. Thanks

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It's a wheelbase thing, you wouldn't understand.

depending on year, engine, build, 2wd/4wd, towing package, etc you could have anything underthere. with that said, the most common gear ratio's in the suburbans are
2wd's:
Standard packages, all engines, 3.45/3.55's,
Trailering Special 350 3.73,
Trailering special 400 3.55,
Trailering special 454 3.08, 3.73

4wd's,
Standard gearing was 3.73 or 4.10 for 350/400's, trailering package seems not to matter.

this is what I've seen in the dozen or so suburbans I've dealt with, and with my menagerie of them
73 C10 trailering special 454/400 3.73 12 bolt rear,
73 K20 trailering special, 350/350/4.10 14bff,
77 C20 trailering special 454/400 3.08 14BFF[pretty sure from the rotational test, although I still need to tear the cover off, and check the stamps]
76 C10 (friends) 350/350 3.45 12bolt
81 K20 350/400 3.73 14bff
73 K20 (friends) 350/350 3/73 14bff

as you can see, a majority of my experience is with the older trucks... the newer ones with over drive could have higher ratio's such as 4.10's, and 4.56's stock since that overdrive can help take care of some of the extra spins needed. if you havn't tampered with the axles in your sub, and the previous owner(s) havn't either, I'd say its a pretty safe bet you've got 3.73's. that seemed to be a pretty standard size for most 4x4 suburbans.

as for a code in teh glove box, 90% of all build sheets will give you the axle ratio in black and white. my old C20 pickup had it written right there on the tag, my friends 76 suburban has it marked on the tag, but my 77 c20 trailering doesn't give an axle ratio... just that it has trailering package whatever. real pain with it lumping everythign as part of the trailering package, since not everythign is as obvious as the electric trailer brakes, or the secondary batery isolater for the trailer, or the class3 hitch... like the unobvious heavy duty brake option ( 13 inch rears, as opposed to standard 11 inch rears)

hope that helped a little, or you were able to make some sense out of it...

-Rich

My truck isn't ugly, you have a skewed sense of beauty

<font color=blue>2007 Ford XLS++ intrepid Ram Superduty 7000 R-type's suck</font color=blue>

Thanks, every little bet helps.

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It's a wheelbase thing, you wouldn't understand.

every little bit helps allright, but I bet you anything, its been more then 40,000 miles since the differential oil was changed in your truck, so you should just pull teh cover, inspect the gears, and put in new fluid.... ( the manual suggests once every 30,000-60,000 depending on light, or heavy use... )

I can't really say much, since my trucks are probably well overdue for a gear oil change...

-Rich

My truck isn't ugly, you have a skewed sense of beauty

<font color=blue>2007 Ford XLS++ intrepid Ram Superduty 7000 R-type's suck</font color=blue>

Actually, I'd say the standard was 3.42 gears, the option was the 3.73. I hear a lot of Burbs cruising with 3.42 gears.

Red 1989 GMC Suburban SLE V1500 - TBI 350, 700R4 w/ shift kit, Quad-shock front, 31/10.50/15 Pro Comp MT, 4.10 gears, Duals off cat

I bought the 14Bolt FF yesterday. I'm going to change my front to match. I figure I'll try the gear install myself. The axle is out of a 77 1 ton camper special. I never pulled the cover, but I work with the guy and he never had rear end trouble. We'll see what happens. Thanks for the help.

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It's a wheelbase thing, you wouldn't understand.

Ive got 3.42s in my burb. My Jimmy came with 3.73s though. Go figure.

86Jimmy 4"&35"MTRs,87 burb 4"&33"MT,69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>

my 85 4x has 3:42s with the factory tow pack and the sticker is on the glove box door.
goodluck

"well,are you gonna pull them pistols,or whistle dixie!?"

According to a previous GM at the local Checy dealer, "standard" gears depended totally on whta part of the country the vehicle was originally shipped to. I have an 88 Burb w/ 3.42 gears. Most vehicles with these gears came from the midwest area originally. Most of the Rocky Mtn regions came with 3.73 originally.. At least this is what I was told. I made sense to me.

BurbLover

According to a previous GM at the local Checy dealer, "standard" gears depended totally on whta part of the country the vehicle was originally shipped to. I have an 88 Burb w/ 3.42 gears. Most vehicles with these gears came from the midwest area originally. Most of the Rocky Mtn regions came with 3.73 originally.. At least this is what I was told. It made sense to me.

BurbLover

Glove box should have one of these codes:

GT4 = 3.73
GT5 = 4.10
GU4 = 3.08
GU5 = 3.23
GU6 = 3.42
HC4 = 4.56

Also look for:

G80 = limited slip (positraction).

I have my 14 Bolt FF now. I'll be pulling the cover of to see my new gear ratio this week. I plan on matching the front gears to the new rear. I know I shouldn't buy a rear end without pulling the cover but I know the guy I got it from and it was only $50.

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It's a wheelbase thing, you wouldn't understand.