FMTV High Speed Gears

[Shark Bait]

Found another stewart and stevenson m-1078A1 spec sheet that says cat 3126, with a 3700SP
I'm no master mechanic but from my view all things are pointing to very similar specs on all of these. My biggest fear right now is that the electronics won't jive if i have a 3700 and want to swap.
interestingly the 3070 and the 3700 both list an "integrated transfer case" which just looks like it's bolted on the back where the drive line would normally attach (like on the 3500) both parts show a 20 bolt pattern (ish - i didnt count every bolt). Im going to go ahead and post the spec sheet diagrams so it makes more sense. If mine is already a 3070 then no swap would be needed. It already has the .65 7th gear. If thats the case however then mine should do better than 55 max, assuming 2500rpm governor.
once the diffs are swapped it should be mid 80's when wrapped out. Not that i plan to drive 80, but cruising along at 1800-2000rpms has got to be better on mileage! I hope.

any idea where the model number would be located on the case? Mine (truck) is taking forever to ship here. Was supposed to be picked up on the 21st, and last i heard they were "for sure" going to pick it up this morning.

Mine has the 3070 and will push to about 58mph, however, once that 48-50 threshold is surpassed the little Cat does want to push up the heat. These trucks are comfortable at the 45-50 range. Mine doesn't have a tach so I don't know the RPM's that it is cranking at those speeds. I do not believe changing these transmissions would be a beer drinking fun time with a buddy or three. I have two 3070's in the crates and I believe they're close to a ton each (with crate). LIKE don't care to change anything on mine because of the mountains here and I'm not in a hurry to go anywhere with it. I'm used to the HET topping out at 48mph, that's the one I'd like to squeeze 10 more mph out of. Lol

Dave

 

[Mike Wryley]

Please tell me from whom ??

Thanks

Mike

 

[coolas]

hi Steve if you have taken the gears out of the housing can you give me the numbers stamped on the crown wheel and pinion cheers Brad

 

[Duckworthe]

So for those of you who have done the MRAP gear swap, have you found any negative side effects yet? Examples, trans running hot, driveshaft issues, tire issues? I have many friends who are mog owners, I know I know apples and oranges, but they have hub issues after and trans overheating. Just wondering. I don't want to get going down a path that has chain reaction results. Just looking for info since time has passed on this post.

 

[tburk49760]

So for those of you who have done the MRAP gear swap, have you found any negative side effects yet? Examples, trans running hot, driveshaft issues, tire issues? I have many friends who are mog owners, I know I know apples and oranges, but they have hub issues after and trans overheating. Just wondering. I don't want to get going down a path that has chain reaction results. Just looking for info since time has passed on this post.

I have done the regear and it is my favorite mod so far... No issues at all. Used Lucas addative and hub temps are half of what they were. Search my many posts, I'm very opinionated.

 

[trackhunter]

Just wondering if this idea worked I have a mtv front and 1 rear axle with 3.07 gears. I have an Lmtv with stock 3.90 I am hoping the pinion inside the mtv rear axle is the same.

 

[trackhunter]

Love the gear swap idea.

I am wondering, would the three axle FMTV allow for the gear swap as well? IE would I simply order three sets, and it should go, or does the middle axle with its drive shaft coming in from the top ruin this for me? Would LOVE LOVE LOVE To go 75 mph!

Thanks

Sorry should have attach this to the above post

 

[scottmandu]

Just wondering if this idea worked I have a mtv front and 1 rear axle with 3.07 gears. I have an Lmtv with stock 3.90 I am hoping the pinion inside the mtv rear axle is the same.

The MTV front axle and the MTV rear axle is the same, the center one is different as it has a different 3rd member.

 

[lmtvjunky]

bump

 

[tennmogger]

Does anyone happen to know the tooth count on the ring and pinion that yields the 3.07 ratio?

Thanks

 

[tennmogger]

43 / 14 = 3.07

Any reports on actual fuel mileage after the gear swap?

 

[tburk49760]

About 8mpg working it hard. If I drive real gentle... I've gotten 9 plus.

 

[scottreb]

Has anyone done the swap with a MTV yet? Curious to know if there were any issues with the center axle R&P swap.

 

[radbad]

After reading 153 posts about the differential swaps, it seems I'm pretty late to the party.

Are there anymore of these axles/differential gear sets lying around? Is it worth calling any of the wreckers/scrappers that had them before, or is everyone out?

Anyone on the site have some they're selling?

 

[steve6x6x6]

After reading 153 posts about the differential swaps, it seems I'm pretty late to the party.

Are there anymore of these axles/differential gear sets lying around? Is it worth calling any of the wreckers/scrappers that had them before, or is everyone out?

Anyone on the site have some they're selling?

You asking about the RF-19 Meritors axles that are used in the M1078A1 and up? Brand new with 3.07 / 6.14.

 

[PowerstrokeNC]

43 / 14 = 3.07

Any reports on actual fuel mileage after the gear swap?

I get 10MPG at 60MPH in my LMTV, mine has a 290hp 3116 if that makes a difference. This was calculated on 400 mile trip.

 

[Keith Knight]

steve6x6x6 I tried sending you a PM but your box is full.
I live 45 minutes south of you in Wauchula, FL, and interested in changing the gears in my M1078.
How could I get in touch with you?

 

[DanM7890]

I am not local but would love to get my hands on a set.

 

[coachgeo]

Another source also in FL is Bryce Wasielak. Look him up on facebook. Also he's the fellow who took the time go to CO? and install ones he sold a member here to install them.

 

[radbad]

You asking about the RF-19 Meritors axles that are used in the M1078A1 and up? Brand new with 3.07 / 6.14.

Steve,

I have an M1079, so same family. Looks like you have quite a few of these axles stocked up!

What do I need to check on my truck to know if they're compatible?

I'm looking to do a swap of the differential gears ets and not the entire axles - I don't have the facilities to drop and replace an entire axle.

Happy to get in contact wit you directly to discuss if you have contact info I can use.

Cheers!