I’ve decided on a gear swap and need you guys to educate me so when I talk to some shops around here I don’t get taken and can come across somewhat intelligent.

I have a 2006 QC SLT 3.7. This truck is a dog compared to my 2nd Gen 3.9. 90% of driving is city and I tow a lot. I have the 4sp auto with 3:55 and LSD. I think the only way I am going to get the "grunt" I want is with a gear swap. I am thinking 4:10 instead of 3:92. I’ve searched the boards and googled everything I could. Will my factory LSD work with the new gears? I need to find out what size rear-end I have. I have not been able to locate.

What else isinvolved. I was looking at JawsGear.com? Anyresources oronline retailers to consider?

Go ahead let me have it! I need all the input I can get! Thanks.

 

go with 4.56....

Very steep. You'll appreciate it.

 

with the gears you are gonna go with the rpms will be off the scale. as far as the rear end. open up the glove box and look at the back. there should be a sticker with the info. as far as the gears. they will work as long as you have the correct ring and pinion. you may need to shim it differently. any decent gear shop will be able to help you out. not to many people familiar with rear ends.

 

4.56 sounds a little low. I have a 3.55 lsd and it is a 9.25" corporate rear end I think.

 

4.56 is a steep gear, whihc is what I'm thinking he wants.

Mainly torque and city mpg...

 

Try to find a drivetrain business
that will guarantee in writing
that they will fix any noise or vibration problems
for at least 90 days after installation.

Some problems take a while to show up.

Don't forget that you can 'try out'
the effect of numerically higher gear ratios
by going to a salvage yard and buying some used
smaller diameter tires, putting them on your truck
temporarily and doing some acceleration runs.
Spending $150 exploring whether you should spend
$800-1400 permanently is worth considering.

 

Now that sounds like a pretty good idea... Next dumb question is what tire size shouldI be looking for to bestmimic a 4:10 or 4:56 or whatever. Is there a conversion I can use?

 

3.92 will be plenty 4.10 at the most. if you go 4.56 you will be screamin down the highway(doing 70). I had 4.56 with 38 inch tires and it was a killer comb, but if you are not planning on using 35 or taller tires you will be happy with the 3.92 or the 4.10. that would be murder for your engine. it would be fun getting to speed quick but you willrev out quickly. currently I am running the 3.92 and it has plenty of towing power. Also if you are doing the swap you might want to check out a locking diff theses really help out on slippery ramps. Detroit locker is a very reliable brand they have all kinds air, or automatic etc....thats just my 00.2 good luck and find a good shop!!!

 

Go with the 4.10. Definitely find a reputable shop that does ring and pinion work to install it for you. From what I've seen on here, labor is ususally between 200 - 300. Your stock LSDwill work with the higher gears. But while you've got the rear end apart you might wanna consider what nowick said and go with something different.

Changing the LSD won't cost any more $$$ in labor because it has to come out to do the gear swap anyway. You'll only be out the price of the part. I would go with a Detroit product also, either a Detroit True Trac or a Detroit Locker. Lockers will be mighty pricey though. For the gears, I would recommend Motive. Try nationaldrivetrain.com. They sell the Motive Gears and the Detroit stuff.

I'm assuming your truck is a 4x2. If it's a 4x4 and you change the gear ratio in therear, you haveto dothe same in the front. The front and back ratios have to match.