4.10 or 3.73 ?

m38inmaine

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Would like to change the gearing on my M1031, will be using stock size tires. I changed a M1008 I had to 3.73 and it worked fine, my concern with the 1031 is the weight, 9200lbs, don't want it to be a dog. Thanks.
 

IRWFO

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I think either one is going to make it feel like a dog taking off compaired to the 4.56's. The worst part will be long upward grades where that weight is going to hurt. On the other hand 4:10's should give you another 12-15mph top speed.
 

Recovry4x4

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I'd almost bet it would be cheaper to go to the 700R4 and add a deeper first gear and a .70 OD. You would keep your out of the hole power, actually increase it a bit and add the .70 Overdive. Win win in my observation.
 

acmunro

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The 700r4 is not that fun of a swap with the 1031's PTO powered Generator.
I have also been thinking of a gear swap on a 1031 for more speed using the stock tires.
 
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diesel583

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I'm thinking about 4.10 but that might be the limit with the load I haul. Would do it if I could find the parts to make it a duelley. It's a little top heavy on rough ground.
 

m38inmaine

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Is the OAL of the 700r4 the same as the 400?, if so I think the swap would be ok, if not the pto shaft length would have to be changed.
 

diesel583

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Mark I think it's longer, it's been a while since I looked at a 700. I think all the shafts will have to be modified. And the crosmember may have to move. Been about 15 years since I done a swap.

If you still need the welder shelf I'll unload mine and get you a few picture and a print in a couple of weeks, got to go back to work.
 

1956_4x4

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The 3.73 gears work fine. I've been running them in my 1031 for a long time now and don't have any complaints. I also run 33" tires with these gears. If you are going to change the gears, I'd recommend changing the rear only and driving it to see if it performs to your expectations (just don't drop it in 4wd...). If you are happy with it, then regear the front differential too.

The 700R4 is the way to go if you have the time and money. Swapping the gears worked for me.

Smitty
 

11Echo

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I've been running 3.73 gears in a handful of 4x4's going back over 30 years, most with 33" rubber. Most had T400, some were T350 and 4 speeds. Never any problems but, they were gassers. Four of them were 1 ton duallies. I ordered the 1977 K30 with 4.10's but went back to 3.73 after that.
 

84cucv1ton

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what other gears came from the factory? i only know of 4.56 and 4.10. the axles all over my yard are those to ratios and thats it. had a 3.73 14b that was a 2wd gas truck.
 

11Echo

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what other gears came from the factory? i only know of 4.56 and 4.10. the axles all over my yard are those to ratios and thats it. had a 3.73 14b that was a 2wd gas truck.
Some GM 3/4 tons had 3.21, 3.42, and C30 a 5.13 FF rears.
 
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AJMBLAZER

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3.73 was a common one in the 4x4's. Around here you find more 8 lug trucks with 3.73 gears than 4.10's and 4.56's are almost unheard of.

We discussed this on CK5 and someone pulled out the GM parts list and showed the 3.21 and 3.42's and even a part number for a 2.72(?) ratio for a 14FF. No clue what they'd have used it in though.
 

truck0590

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Although the 700r4 or 4l80e would be the ideal options, it is a pain to do with the NP205 since only a rare hand full were produced that ever bolted to a 205. Spline count is different then NP208. There has been disussion out there and a couple of folks have done it, but not very many.

Truck
 
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