Front diff went out What's good ratio to put back in?

[skeeternash]

I have a 1995 chevy tahoe running 3.42s and was wondering if 3.73s would be better put back in it or the original back. I'm looking to do a little offroading and i am running 35 inch tires on 20 inch rims. Any suggestions?

[trkklr77]

you need to match your rear ratio so if you arent going to do the rear you had better put the same back in


most people are running excessivly higher gears any more because you o/d will make up for the lost top end speed.
4.10/4.56

[skeeternash]

I plan on doing both for sure just don't want to turn into a gas sucking machine would 3.73s make that big of a difference mpg wise?

[trkklr77]

as always, its a balance of power exerted v rpm spun

you can run 3.00 and only spin 1600 @65 but be 3/4 pedal to keep it going.

or

you can run 4.56 and spin 3000 @65 but only be @1/2 pedal.

ie less effort to push the same brick of shit.

[sjracer]

3.73 came stock in alot of 1/2 and some 3/4 ton trucks so if your going economy you may be able to pickup a set of gears super cheap or find a whole new front or rear axle the wrecking yard fairly cheap. 4.10's usually came in 3/4 ton and larger axles. also different differentials have different carrier breaks, such as 12 bolt carriers had two different carriers and the break point in those diffs is 3.73 and lower/ 3.96(?) and higher numerically, so you may have to buy a different diff carrier in one or both diffs to do some serious re-gearing. might be time to upgrade your diffs anyway as you probably have 10 bolts front and rear in that tahoe.
isn't a tahoe IFS anyway? might be time for a straight axle swap.....

[1GMC4x4]

I have a 94" GMC and when I had my IFS I had 3.73s with 35" Tires. It worked. 65mph was around 1800RPM with my Auto(4L60E) but it had no balls! And towing sucked.

I am now running 4.10 with 35s until I install my 37s and it has WAY more power. Its like a new truck. I have never been able to roast my tires and now I can almost go through first gear shredding them up.

65 is more around 2100 but like said above, the engine works way less to get there.

[Suburbiangiant]

I'm running 4.56's and 35's right now and I gained mpg by switching. The stock 3.73's just weren't enough to turn 35's in a heavy suburban.

With your vehicle being geared high I would swap to 4.10's and you would basically have the bone stock vehicle characteristics again. Your MPG would more then likely be better then it is now. 3.42s and 35's is just horrid.

[skeeternash]

Don't you all mean 4.11's I'm not sure there is a 4.10 is there for my truck?

[trkklr77]

does 1 hundredth of a gear rotation realy matter?

and depending on eaxctly what axles you have you can have 4.09 in the front and 4.11 in the rear

[skeeternash]

Ok just wondering I'm not entirely knowledgeable on the whole gear changing this will be my first. Thanks for the great info from everyone. I was originally planning on putting 4.11's in it, but some people I know told me it would kill my gas mileage. Just wondered what everyone else thought

[K5runner@hotmail.com]

When I had my 2500HD with a 6.0 it had 3.73 and 35's. I hated it it couldn't choose a gear to stay in, especially while towing. I put a set of 4.88's it was the best thing I ever did. Even though everbody told me I was wrong . Towed awesome, felt like it had more umph. I did not notice a change in mpg. Also it was a crew cab but I was on 16's. If I were to do it again I would.

[axisT6]

Originally Posted by skeeternash

I was originally planning on putting 4.11's in it, but some people I know told me it would kill my gas mileage.

Those people are ignorant. MPG is function of engine load and RPM. Engine Load has a greater effect however.

Lower gears provide more mechanical advantage which is needed in a heavy vehicle with big tires. That said, you have less engine load at any given RPM with the lower gears, but your RPMs will be higher.

[gee whizz]

Originally Posted by skeeternash

Ok just wondering I'm not entirely knowledgeable on the whole gear changing this will be my first. Thanks for the great info from everyone. I was originally planning on putting 4.11's in it, but some people I know told me it would kill my gas mileage. Just wondered what everyone else thought

kill your mileage? how about those 35's what did your friend say about those? yes if you had a completely stock truck and you lowered the ratios it would do something to the mileage.
the whole point is to match your powerband back to stock. so take a gear calculator and plug in your stock #'s and tires and try to match that with 35's with your new gear ratio.

[skeeternash]

Thanks guys I think i'm g2g with 3.73s for now but will definitely upgrade to 4.11's if need be

[Suburbiangiant]

3.73's and 35's is useless! If you want good gas mileage again then you need to be at a 4.11 minimum. Don't waste your money on 3.73's that's a lot of dough to throw away and not be happy with the outcome.

Maybe you'll follow a chart rather then opinions.

Yellow = Good Gas mileage
Green = Closest to stock ratio
Red = More torque

[K5runner@hotmail.com]

Originally Posted by skeeternash

Thanks guys I think i'm g2g with 3.73s for now but will definitely upgrade to 4.11's if need be

Wow good job. You definitely learned a hole shit load from this didn't you?

[just4cuz]

I don't think Suburbangiants chart takes OD transmissions into account. If you have a 700R4 or 4l60E multiply your rpms by .70. A 4l80E requires you to multiply by .75 in each of the categories.

[1GMC4x4]

seriously
X2 3.73s are useless for you truck. take it from someone who has had both 3.73 and 4.10 on the same truck with the same size tire.

[trkklr77]

Originally Posted by just4cuz

I don't think Suburbangiants chart takes OD transmissions into account. If you have a 700R4 or 4l60E multiply your rpms by .70. A 4l80E requires you to multiply by .75 in each of the categories.

no it doesnt, it is set to be 1:1.

it also follows the theory of less rpm = less consumption not real world load v consumption.

[Suburbiangiant]

Correct... If you drive an automatic your RPMs will be higher, and the opposite is true if you have overdrive. your RPMs will be lower.