Mismatched Front/Rear Axle Gears 4.56/3.73 - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 03-14-2007, 09:20 PM   #1 (permalink)
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Mismatched Front/Rear Axle Gears 4.56/3.73

I am just wondering exactly what happens when you use 4wd with mismatched front and rear axle gears? I know it isn't good and they will be fighting each other but I have never done it and was wondering if anyone has and what actually happens? I'm just curious because I am selling my 1996 Chevy Silverado which has 4.56's in the rear and I never got around to putting 4.56's in the front, so it's still stock 3.73 in the front, and I never use the 4x4 anyway....but I just want to tell the guy who is buying my truck exactly what will happen if he uses 4x4 without re-gearing the front. Thanks for the help
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Old 03-14-2007, 09:28 PM   #2 (permalink)
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depends on the situation,

if your are running appropreatly mismatched tires, nothing
if you have a part time tcase [205,208,241..... not the 203] it will 100% bind up and something WILL break.
a 203 has a differental built into it and will allow some slip but not that much.
it will wear teh living shit out of the tires if it is engauged.
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Old 03-14-2007, 09:30 PM   #3 (permalink)
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ther eis a formula somewhere that can tell you what size tires to run with which gears SPICIFICALY FOR MISMATHED GEARING.

it may be % of gear ratio offset = same % of tire diam offset
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Old 03-14-2007, 11:12 PM   #4 (permalink)
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Just bolt some 37s up in back and tell the buyer it's part sand rail!

No, seriously, nothing good can come from this assuming 4 identical tires. You should get the front gears put in, or at least tell him he's gonna have to before he uses the 4WD.
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Old 03-14-2007, 11:52 PM   #5 (permalink)
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if you do this your going to break something... ive been there... 3.55s up front and 4.88s in the rear. it will plow in the snow, gravel is OK, mud you couldnt tell, but dirt it will feel like the truck is bending in the center like a stick. your truck is goings to try to spin the front end almost a full turn compaired to the rear... id tell the guy to gear it or not use it. those front ends arent cheap-and neither is the transfercase...

or
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Old 03-15-2007, 09:50 AM   #6 (permalink)
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I had an old flatfender I changed the front axle in and didn't even think about the gears. 5.38 rear, 4.88 front put it in 4x4 at loon lake and ran the whole rubicon put 70 lbs. of air in the tires and chirped and hopped all the way. Never broke anything (real light with skinny tires and 4 banger) but I don't recommend it.
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Old 03-15-2007, 01:40 PM   #7 (permalink)
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Something is going to ******* break. That is about the dumbest & dumber!
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Old 03-15-2007, 01:43 PM   #8 (permalink)
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i replaced an np231 on a 2 door blazer that was broke in half because the guy didnt want to put new gears in the front
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Old 03-15-2007, 04:51 PM   #9 (permalink)
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Quote:
Originally Posted by quikchevyz71 View Post
I am just wondering exactly what happens when you use 4wd with mismatched front and rear axle gears? I know it isn't good and they will be fighting each other but I have never done it and was wondering if anyone has and what actually happens? I'm just curious because I am selling my 1996 Chevy Silverado which has 4.56's in the rear and I never got around to putting 4.56's in the front, so it's still stock 3.73 in the front, and I never use the 4x4 anyway....but I just want to tell the guy who is buying my truck exactly what will happen if he uses 4x4 without re-gearing the front. Thanks for the help
to specifically answer the question, the front tires will turn faster than the rear tires. on any high traction surface, it will bind and break something
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Old 03-15-2007, 05:18 PM   #10 (permalink)
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it would either pull apart or the axles would pull towards each other
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Old 10-23-2014, 12:37 PM   #11 (permalink)
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MisMatched Tire Sizes

on my z71 I had 31 streets when I bought it. I don't have enough clearance yet to put my new 35 toyo's on the front. I had 2 blowouts, and decided to put the 35's on the rear.

So now I have 31's in the front, and 35's in the back, and I'm scared to use 4x4. I did accidentally had 4wd engaged when I drove off once and left tire marks like a burnout.

I'm thinking about being stupid/smart and changing the rear axle ratio so my tires will match up

Do y'all think I can get the ratios close enough, or will the front and back always be slightly off until I install the lift kit and fronts
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Old 10-23-2014, 07:01 PM   #12 (permalink)
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Considering those are 17" wheels in the picture, your tires are not exactly 35's nor exactly 31's. I'm guessing 265/70R17's up front and 315/70R17's or similar in the rear? Maybe 305/70R17 rear?

Anyway, re-gear the rear axle so you get your power back. Leave it in 2HI until you can afford to lift the front to clear the same size as you have in the back, then re-gear the front...or SAS the front. With 35's and a 5.3L auto, I'd shoot for 4.10's for highway mileage, 4.56's for all around good power and 4.88's for offroad.
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Old 10-23-2014, 08:53 PM   #13 (permalink)
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Necro thread.......
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Old Yesterday, 11:11 AM   #14 (permalink)
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Quote:
Originally Posted by svt150j49 View Post
it will plow in the snow, gravel is OK, mud you couldnt tell, but dirt it will feel like the truck is bending in the center like a stick.

pretty much, ive actually done this with two trucks. my daily driver for a year had 3.08 in back and 373 in the front, if there was heavy snow on the ground i didnt notice at all. that truck never seen mud.

my k5 blazer i took offroad in the middle of the axle swap, 2.73 in the back and 3.73 up front. i just left it in 2wd til i got stuck in the mud, engaged and took it out soon as i got out of the mud but doing it on dry pavement wont work, it basically binds up and it feels like it slams on the brakes
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