Absolutely I hear you about wanting to save some money, and I hope you can get it to work. Finding a stock 4.10 rear end and buying the front gears to match should work just fine. If you do find a rear end from a 2wd, you'll have to swap the gears to your 4wd axle since the 2wd are even narrower than the 4wd, somewhere between 3-4" narrower. I assume that's what you're already planning on doing.

It sucks to see anyone's ride sitting in a lot, let alone when its a nice ride that you've put a lot of time and effort into. I get how frustrated you're feeling, and we're trying to help provide the best information we can to help get you back on the road. Good luck!

 

Oh no... the trucks BEEN back on the road! I found a whole axle with matching gears, drum brakes and only 60K on it - all for $200! These questions I'm asking about the 4.10's are for a spare rear/front differential I'm going to start building!

 

I'm also thinking about a gear swap. i have 31' tires and 3.42 gears and horrible gas mileage on my 97 LS 4x4 blazer. exactly which 4.10 ring & pinion should i buy for my front diff? i'd like to put 33' tires under it. i'm thinking if it's not cost effective i'll just go to 3.73's.

 

How does going from 3.42 to 4.10 help improve gas mileage?

 

It usually would not help milage, but if you put bigger tires on, the drivetrain has to work much harder to get it up to speed, so with the lower gear ratio (higher numerically), it is a lot easier for the vehicle to get up to speed so you would get better mileage at least in town and more then likely under all driving conditions

 

I can see that would be a small factor. We went with 225/70 19.5 vs the old 8R 19.5's on the MH (454 TBI) lowering the gearing 2.5% and increased MPG by 1+ on the 8000 mile trip we took last year but the 4L80 automatic is just geared too high for a 100% time/weight loaded truck.

We are looking to replace our rear end as a unit because of spider gear wear due to half million miles. Initially I was thinking of bumping up from the 3.08 ratio in the 1998 2WD 5-speed S10 but I really may never tow/haul much with it. It takes off OK with the 3.08 and if I do tow I can just run it in 3rd or 4th gear depending on the road grade.

When loaded heavy I have found engines (Chevy) will give best MPG at 3000 +/- 500 RPM. Then that is common knowledge here because that is the sweet spot for torque/HP production.

 

sorry I had to revive this a bit. this is the info I have been searching for. I have 98 4x4 now if I didn't use the 4x4 would I still need to upgrade both gears? also whats the differential size in the front and rear for mine? new to the truck tunning

 

I agree that your gas mileage will get worse, but maybe you dont care

 

You can find your RPO codes in your glove box. That will tell you which gear ratio you have now. There is a list on the first page of this thread that will tell you the codes for the various gear ratio's available on s-series trucks. The most common on Blazers is 3.42 (GU6) and 3.73 (GT4). I'm almost positive that all ZR2's came with 3.73 gears.

As for driving with miss-matched front & rear axles, you would be fine as long as you don't have a Bravada with AWD, and as long as you disable the 4x4 by pulling the fuse. This will prevent the front axle from engaging. If you were to engage the 4x4 with miss-matched axles while moving you WILL break stuff. I drove mine for 3 months after swaping my rear axle before I could get the front changed to match.

 

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