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M1009 to M1008 differential gear ratio swap

powerwagonwc12

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I would like to change my 456 gearing to 308 in my M1008, this set up 6.2/TH400 and 308 worked well in my previously owned M1009 and would like to duplicate this to my M1008 any advise ?
 

87cr250r

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The 14 bolt full float axle was only built as a heavy 3/4, 1, and 1-1/4 ton axle. 4.10 is the 1 ton ratio and you know your 1-1/4 M1008 is 4.56. There is probably a 3.73 option, otherwise, I don't think you're going to find any lower ratios.

The M1008 cruises at 65mph ok. It has some serious drone issues. I would consider adding a crossover pipe to the dual exhaust. The civilian trucks had a muffler on the intake but it doesn't clear the dual batteries.

That's actually why I chose to turbo mine, the turbo works to muffle both intake and exhaust sides.
 

adf5565

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If you decide to go that route, you will have to change the carriers. And that is quite expensive at the moment...
Carriers sure aren't cheap right now.

On that note, something I've always wondered, from what I've seen 4.10 and lower require a different carrier. However USA Standard Gear (and probably others) sell a 4.11 ring/pinion. I'm assuming this still requires the different carrier? Or would this fit on the existing one?
 
Last edited:

powerwagonwc12

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Steel Soldiers Supporter
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College Station, TX
The 14 bolt full float axle was only built as a heavy 3/4, 1, and 1-1/4 ton axle. 4.10 is the 1 ton ratio and you know your 1-1/4 M1008 is 4.56. There is probably a 3.73 option, otherwise, I don't think you're going to find any lower ratios.

The M1008 cruises at 65mph ok. It has some serious drone issues. I would consider adding a crossover pipe to the dual exhaust. The civilian trucks had a muffler on the intake but it doesn't clear the dual batteries.

That's actually why I chose to turbo mine, the turbo works to muffle both intake and exhaust sides.
I would like to turbo mine but I am having issues locating parts at a reasonable price or at all.
 

Mullaney

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What is a carrier?
.
Best / Easiest answer explaining what a "Carrier" is in a differential would be to search "differential-carriers" maybe even at Summit Racing. They have a lot of things available that might be useful for you. Including gear sets and bearings.

EDIT: And @deank has the TM (Technical Manual) picture and item number for you.

.
 

LT67

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Bowdon, GA
Carriers sure aren't cheap right now.

On that note, something I've always wondered, from what I've seen 4.10 and lower require a different carrier. However USA Standard Gear (and probably others) sell a 4.11 ring/pinion. I'm assuming this still requires the different carrier? Or would this fit on the existing one?
If you have an existing carrier for 4:10 and numerically lower, thick cut gears are available for a numerically higher gear ratio
 

adf5565

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If you have an existing carrier for 4:10 and numerically lower, thick cut gears are available for a numerically higher gear ratio
Yep, makes sense. Unfortunately I believe the m1008 came stock with the other carrier. I was just curious if 4:11 fell into the “4:10 and down” carrier since technically it is numerically larger than 4:10. But I’ve always considered 4:11 and 4:10 to be the same thing (which could be wrong) so I just wanted to confirm the 4:11s still would require the different carrier.
 

LT67

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Yep, makes sense. Unfortunately I believe the m1008 came stock with the other carrier. I was just curious if 4:11 fell into the “4:10 and down” carrier since technically it is numerically larger than 4:10. But I’ve always considered 4:11 and 4:10 to be the same thing (which could be wrong) so I just wanted to confirm the 4:11s still would require the different carrier.
The existing carriers in a M1008 is for 4:30 and numerically higher gears
 

nyoffroad

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A 700r4 conversion might be a lot cheaper and can be done easy enough for beginners in a driveway.
No disrespect meant but if you have to ask what is a carrier, then that project isn't really for you. Lots of experienced mechanics shy away from rear gears.
 

deank

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A 700r4 conversion might be a lot cheaper and can be done easy enough for beginners in a driveway.
No disrespect meant but if you have to ask what is a carrier, then that project isn't really for you. Lots of experienced mechanics shy away from rear gears.
Very true! The last time I rebuilt any axle was about 1985 while working as a technician for a pontiac dealer.
 

powerwagonwc12

Member
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College Station, TX
A 700r4 conversion might be a lot cheaper and can be done easy enough for beginners in a driveway.
No disrespect meant but if you have to ask what is a carrier, then that project isn't really for you. Lots of experienced mechanics shy away from rear gears.
Thank you, None taken. I have no intention of changing (rear gears) in an axle I simply request information to find the optimum gearparts for the application to get the desired outcome. I am an Automation Tech. retired from a chemical plant and would prefer to keep my hands clean. How ever when I was a young man I worked for Ryder systems the worlds largest truck rental and lease company as a Diesel mechanic for several years were I learned among other things I did not want to get my hands dirty for a living.

Thanks for bringing this topic up, Is the 700r4 durable enough for this application? I mean verified miles/ years of service? Thanks.
 

pete-vt

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Buffalo NY USA
What is expensive?
I would be happy if I could swap carriers and gears in both axles for less than $800. And I work in a heavy truck shop for a living. I considered the 700R4 also, and it is indeed the easiest and cheapest way to go. It drops your cruise RPM down low enough at 60, that the motor is not struggling. I do have some reservations about it though, it needs to be built by a reputable builder, for heavy duty service. The 700R4 was intended for lighter vehicles, but with careful planning it can survive.

For my own vehicles I install manual transmissions in everything. Everything I own is a 5-speed.

Either transmission swap can easily be over $2000, with me doing all my own work. So in terms of fuel saved, it takes the entire lifetime of the vehicle for it to pay for itself.

If I was swapping just the gears/carriers, I would keep the stock trans and go with 3.73 gears, with 33-inch tires. It'll get you close enough to what you want, around 2500 RPM at 60.
 
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