Drive axel gear ratio

[925A1]

I hope that I did not miss an old thread about this question. Can someone provide any results with changeing the ring and pinion on M series trucks to obtain greater highway speeds? I would like to keep the axel assemblys and change the gear ratios. I do have a number of truck tractors that I use for parts, that may contain suitable replacement parts. Any advise or comment?

Thank you,

Mark.

 

[mdmorgan]

I'm not sure what the thread name is but it has been talked about, I remember reading through it a while back. Good luck in your search.

 

[steve6x6x6]

There are two outfits that sell a ratio change for the M35A2 and M35A3, when you buy the gears and bearings and seals, then the labor for gear setup your around $1,800.00 per chunk. Good luck.

 

[Kohburn]

if you have the parts that work then go for it - but if you have to buy parts then just get the transmission gear upgrade - it costs about the same as replacing the gears in only one of the 3 axles

 

[Flyingvan911]

I agree on the overdrive in the transmission. This way you also have the lower gear ratios in the lower gears for times when you need that power for slow, heavy pulls.

 

[JasonS]

I agree on the overdrive in the transmission. This way you also have the lower gear ratios in the lower gears for times when you need that power for slow, heavy pulls.

You've got the low transfer case range for this.

 

[Goose2448]

But if you change diff gears, your final drive ratio in each gear goes up rather its high or low tcase gear. I too vote for a better OD trans gear, or trans swap. The 925 goes fast enough, assuming yours does more than 40

 

[JasonS]

But if you change diff gears, your final drive ratio in each gear goes up rather its high or low tcase gear. I too vote for a better OD trans gear, or trans swap. The 925 goes fast enough, assuming yours does more than 40

I am not saying that the transmission gear set isn't the easiest and most cost effective solution. It is what I would do. However, I don't believe that the shift up in each gear is necessarily a bad thing. First gear is plenty low even in high range. Depends on the tires you are running and the expected loads.

 

[Rambling Wreck]

Mark, which "M series" truck do you have?

If you have an M35A2, there is overdrive gear/kit that a member here makes and it will get you the highway speed you desire without compromising low end torque. The cost of this is relatively cheap when you consider your other options.

If you have an M35A3, axle gears or a transmission swap would be the way to go. Unfortunately, to my knowledge, no one has found a compatible automatic transmission that will fit. If they have then they haven't shared it on this site. Some have talked about mating the Spicer manual transmission in the A2 to the Cat 3116 in the A3 but I don't think anyone has actually done it.

Check out this thread for some useful information:
http://www.steelsoldiers.com/deuce-...ompatible-transmissions-m35a3-cat-3116-a.html

Regardless of which truck you have, larger diameter tires will aid in gaining top speed. However that can be relatively pricey when you consider the nominal increase that will get you. That is, unless you are going from really small to really large tires but really large tires require either extended dog bones, bobbing, or bobbing and lifting.

Also, be careful talking about top speed on this site. Some members get really upset if they hear that you want to cruise at more than 55mph.

Welcome to the site!

 

[925A1]

I should have clarified the drive train. CAT 3116 with 4 speed Allison, the truck has 935 tires on. I was hoping that a transmission swap may have been done that proved worth the cost. I have added manual transmission to diesel engine equipped with auto transmission. That conversion was on a swamp buggy, that could be driven at highway speeds and still provide low end in the woods. Fabricating the plate was difficult. The 109A4 just does not look like it will have the room under the cab to do that type of alteration. I will keep my feelers out for a auto transmission that might work. I sure would like one more high end overdrive gear. Thanks for the replies.

Mark.

 

[Rambling Wreck]

Keep us posted as several of us are real interested in this topic.

 

[nmdata]

I am running the equations on a different transmission configuration, 60mph with the engine rpm at 1950, the 5th gear od ratio would be 3.577:1. taking the standard 37" tire footprint. from what i have read, the engines optimal efficiency range is between 1900 and 2000 rpm, so at 60mph the 5th gear ratio would have to be 3.577:1, for a 42" tire at 60mph running 1950rpm, the ratio would have to be 4.061:1 .

does anyone else have the math to figure this out and verify for me? also has anyone found shop that can make the change? this would be something that should bring the fuel economy up to approximately 18mpg, therefore increasing your range on a 50gal tank to 900 miles. according to my calculations, ideally it would be 23mpg but i also am figuring an increased load on the engine and therefore slightly more fuel use. so the 18mpg is a compromise. this is also figured for running singles on the rear.

give me some input on this guys.
thanks in advance

 

[Rambling Wreck]

I'll give this some more time later to actually check the numbers but I need more information first. Please elaborate on what you mean when say "different transmission configuration". If you mean another transmission model entirely, please share.

One thing I can tell you is that you will not get 23 or even 18mpg unless you are rolling down a mountainside.

 

[nmdata]

theoretically the 3053a can be re-geared. would a t-226 transfer case work on a m35a2? im thinking about getting with the manufacture of the 3053a and see if they would be able to supply or at least make a custon gear set for the duece. so for your answer, same transmission, just a different setup. i know it is possible because one of the guys here in town has a 6453 transmission in his 5 ton and got a different gear for 4th and 5th and is able to do 65mph at 2300ish rpm and averages around 13-14 mpg. seeing as the duece is slightly lighter it should equal out to a slight increase in efficiency as well.

 

[gringeltaube]

theoretically the 3053a can be re-geared..................im thinking about getting with the manufacture of the 3053a and see if they would be able to supply or at least make a custon gear set for the duece........

Good luck there...
And FYI, that has been done "in house" already... read this thread or directly go to this web site.


Also, please re-read the forum rules: cross posting the same post within multiple existing threads is not allowed!


G.

 

[Holub9097]

Does anyone know where to get the pinion gear set to raise the gear ratio? I’m trying to get better gas mileage and higher overall gear ratio/ faster speed. I have an m36a2 so I won’t be hauling anything nearly heavy enough to warrant such a low gear ratio. I just want a little more speed and better fuel mileage. I don’t want to use the transmission over drive kit.

 

[cattlerepairman]

The transmission OD kit is no longer available. You could go to a web site that calculates gear ratio and speed, including tire size, and see how much switching to taller tires would help your goals.

 

[Holub9097]

I know the transmission OD kit isn’t available but what about the kit to change the gear ratio at the differential?

 

[steve6x6x6]

Ouverson has a 5.13 ratio but by the time you put 3 chunks assembly's on the work bench and buy the 3 gear set kits ($1,800 ea.) and some bearings and lots of labor = $7,500. Just go buy some 11.00 tires and be done with it.

 

[59apache]

look at this:

A3 transmission replacement questions

I'm looking for advice, suggestions, examples of similar work, etc. Your help is greatly appreciated. So, I have an M109A4 with a frozen transmission. (yes I know A3s suck, I agree, moving on now...) My issue: If the engine is running the transmission locks up, meaning the output shaft to...

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