Gearing?

[Cigarjoe]

I want to change the gearing in the diffs so the truck doesn't sound like its going to blow up at 50mph. Can anyone tell me what size gear set to use please? I want lower rpm's at 60 6- but still want a descent pulling power. Also what kind of diffs are in the M1008?

 

[steved454]

I am thinking of going from the 4.56 gears to 4.11 gears to increase top speed but still be able to pull something. I have a 41/2 inch lift and fixing to run 35 x11.50 x 16 mud grips. Not sure how much that will cost and what I need to change on the locker either.

 

[Keith_J]

Dana 60 front, GM 14 bolt rear. 4.56:1, you could go to 4.11:1, 3.73:1 or even 3.54:1. But for the rear Corporate 14 bolt, you will need a new carrier since 4.56:1 is as high (low numerically) as you can go. Expensive swap.

Now you could go for an add-on overdrive kit. About the same cost, a lot less work. And no loss of pulling power. Most are 0.80:1, giving you an equivalent of 3.65:1 axle ratios or dropping engine speed by 20%.

 

[4x4 Forever]

I got this from a major online supplier for the back (Corp 14bolt):

Q. I presently have a gm 14bolt rear with 4.56 with a detroit locker. I
would like to go to 4.10 ratio with a detroit locker. Is this possible
and what would i have to change?

A. You need a new carrier or a used carrier 4.10 and down. You can swap your
Detroit over to the new carrier. I have a used carrier for $75 if you need
it. New 4.10's $225 and master install kit $125 thanks,

As far as the front (Dana 60): I would ASSUME about the same, except for the locker, but I have never gone into a Dana 60 before. I'm sure someone with Dana experience will come along shortly with better info on this swap.

This would be WITHOUT labour or changing out bad or worn bearings / seals in either units. The cost is 'up there', taking into consideration the labour, unless you have the tools and can do it yourself. Running 33" tires with this would help emensely, leaving the truck stock, with no lift.

You can use the below link to figure the final ratios:

Gear Ratio Calculator

If you want to know the supplier, you can PM me and I will be more than happy to forward the CO name.

 

[4bogginchevys]

if the D60 carrier has a "lunch box" locker it will switch to the new carrier fine, factory units are not easily switchable. You could get a 4.10 carrier that is factory design(Trac loc) or whatever, if the case is empty you can switch the internal components to the new carrier. I would probably just get an open carrier for the front and be done with it. IMO 4.56 down to 4.10 is a small step, 3.73 is going to be more noticable. A timing tweak/IP also may make up the difference enough, and leave enough power to tow plenty of bigger things. All i'm saying is it's a lot of money and work for a couple hundred R's.

 

[Keith_J]

If the differentials are quiet, let them be. Lot of money and work is correct. If you get one axle done correctly, it is a 3 day weekend of 10 hour days. If you just slap it together, chances are the gears will grind themselves to dust.

Still want to drop the RPMs? Either add-on overdrive or a modified 700R4 with lock-up torque converter. You will have greater torque converter losses with an add-on overdrive, these losses are probably greater than the gains in engine efficiency. Yes, the 6.2's efficiency drops as RPM increases, it is maximum in the 2500-2700 RPM range.

 

[jj9620]

Gearing

Not trying to come off as a stupid question but im genius on gearing but anyway I too have a M1008 with the same problem and I was wondering if maybe I could not find a civi doner truck and just make a compleate swap on axles and make it work or could you take axles from a 1009 and do the same thing I need to change mine too Thanks

 

[1956_4x4]

I went to 3.73 gears in my 1031. For me, this is perfect gearing when combined with this engine/transmission combination. I pulled the carrier for my 14-bolt out of a truck in the junk yard and swapped the gears in the D-60. The gears in the 14-bolt were easy, but the gears in the D-60 took a few tries to get them right.

I don't think I would even bother with the axles in the 1009, since the others are so common.

Smitty

 

[Keith_J]

I went to 3.73 gears in my 1031. For me, this is perfect gearing when combined with this engine/transmission combination. I pulled the carrier for my 14-bolt out of a truck in the junk yard and swapped the gears in the D-60. The gears in the 14-bolt were easy, but the gears in the D-60 took a few tries to get them right.

I don't think I would even bother with the axles in the 1009, since the others are so common.

Smitty

Any impact on mileage? Did you correct the speedometer?

 

[1956_4x4]

Any impact on mileage? Did you correct the speedometer?

I used a GPS instead of my speedometer for a long time, but finally changed the speedometer gears in the transfer case when I was resealing it. It still reads 2-3 miles slow at 65, but it's close enough for me.

I carry so much gear in the box of the 1031 that I don't even bother to check the MPG. I would guess that it has increased, but not enough to matter to me.

Just for your reference, before I changed the speedometer gears my speedometer was reading 52 MPH while I was cruising at 65 MPH. So, to tell the difference in noise etc. try running at 52 then bump it up to 65. It will give you an idea of what to expect.

Smitty