FMTV High Speed Gears

[DiverDarrell]

Ha!! To be honest I can't wait to pass a convoy in mine and see the confused looks. Probably one of the best upgrades I have done so far, besides the locker, that comes in handy as well. G load rating MVT has a max speed of 81 at 95psi. The L load range is 68 at 130psi. FYI I find my indicated speed is 10mph less than actual from 35-45 mph after the gear change. Truck cruises 60mph no problem till you hit a hill (60 is the max speed limit in my area). And I wish I had the exhaust brake of the A1 trucks

 

[10Lugger]

I had such an opportunity to pass a convoy after my gear swap, I just wonder what was said at the next rest.


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[Rebuilder]

Hey guys... I'm working on the gear change right now and it's going great except this last part on the front. What's the trick to removing it? I tried knocking it around with a wood block and hammer but it's not moving. Bigger hammer?

 

[DiverDarrell]

Coal chisel and hammer

 

[Rebuilder]

Coal chisel and hammer

Had to get a bigger chisel but it came apart. The other side came apart no problem.

 

[blhar15]

Does anyone know where to find a set of the high speed gears still? Also is there a way to recalibrate the speedo?

Thank you

 

[Rebuilder]

Does anyone know where to find a set of the high speed gears still? Also is there a way to recalibrate the speedo?

Thank you

Not sure who has gears but here's a thread about the speedo. https://www.steelsoldiers.com/showt...Speed-Gears-Speedometer-Dip-Switch-Adjustment

 

[simp5782]

Bryce in FL had some awhile back if they didn't get washed away in the hurricane.

 

[exon111]

MPT Drivetrain will do it for about $7k. They said they order the gears from Meritor.

 

[Jcbawn]

I talked my Allison mechanic about changing the gears while having my m1078 serviced. He suggested that he can install an additional gear to make it an
“8 SPEED” I want to see if anyone knows enough about these to definitively confirm or reject this claim. Normally I would just tell him to do it, but I feel like he overcharged me big time for the service, so i’m skeptical of his claim..


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[simp5782]

I talked my Allison mechanic about changing the gears while having my m1078 serviced. He suggested that he can install an additional gear to make it an
“8 SPEED” i want to see if anyone know enough about these to definitively confirm or reject this claim. Normally I would just tell him to do it, but I feel like he overcharged me big time for the service, so im skeptical of his claim..


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you can swap the planetarys for a higher ratios and valve body mod. Not sure of the setup. I know they used to turn the older Chevy/GM trucks from 5 spd to 6 spds. I think suncoast did them for awhile. Or still does.

 

[Suprman]

I call bs on that one. How much did he quote you for one bolt on gear? How much to add an extra cylinder to the engine for more power also.

 

[Suprman]

On the RV forums there are posts about 3000 series transmissions all being 6 speeds. Even if it's installed in an RV as a 5 speed. So the 6th gear can be programmed in. It's physically already there just not being utilized. In the lmtv the trans runs all 6 gears (2-7) and the transfer case switched to low range gives you first gear.

 

[scottmandu]

I've not heard of being able to add an 8th gear to the 3700SP, can you provide additional information?

 

[big block 88]

On the alison 1000 it takes a valve body change to get the 6 speed. The rumor used to be it was all in the programing. But it takes a vb change and reflash the tcm.

as for the 500 series trans or 2000-4000 series im not sure about. I would assume vb replacement or mods are a must to utilize another clutch pack or combination of clutch packs to make another ratio.

maybe stupid question has anyone put a 6 speed 1000 alis behind the fmtv baby cats? I would "assume" the ratios would be better plus the 5 and six are both od on the 6 speed 1000

 

[simp5782]

you can swap the planetarys for a higher ratios and valve body mod. Not sure of the setup. I know they used to turn the older Chevy/GM trucks from 5 spd to 6 spds. I think suncoast did them for awhile. Or still does.

I know you can add a second reverse to the 4000 series. Allison offers 2 different overdrive ratios .64 and .67 in the 4000 series cases. There is .57 available in the 3000 series cases made by a company that replaces the stock .65 ratio in 6th gear. Its their way of more speed with out an overdrive unit. I am sure the planetary gear for that replacement is not much different than the 4000 cases.

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[coachgeo]

.... There is .57 available in the 3000 series cases made by a company that replaces the stock .65 ratio in 6th gear. Its their way of more speed with out an overdrive unit.....

In the 3000 there 6th is our 7th correct?

 

[simp5782]

In the 3000 there 6th is our 7th correct?

Yea. Their 4th is direct drive rather than 5th.

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[Jcbawn]

He mentioned $2k in parts and $2k in labor..
He also mentioned reprogramming and he said it should get another 10mph. Probably worth the cost if it works. I’ll get some more details.


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[wheelspinner]

I would tread VERY lightly here. Adding a gear will only increase the driveshaft speed, which is already very close to the limits of physics based on all of the testing that the gov't did on several different versions. The last thing I would want to do is speed up the driveshaft even more. Better gears are the much preferred option.