M1165A1 diff gear swap

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ant929
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M1165A1 diff gear swap

Post by ant929 » Sat Mar 06, 2021 1:51 pm

So since my M1165A1 is not carrying armor I was thinking about changing out the 3.08 diff gears to 2.73. Any input? Do I just need to buy the ring ind spindle and have a professional install it? I thought I was going to get to drive over 60 mph with the 4l80 transmission but nope.


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Ted Gates
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Re: M1165A1 diff gear swap

Post by Ted Gates » Sun Mar 07, 2021 7:59 am

My 1152 with 3.08 does up to 70 plus mph. Are you experiencing transmission issues? Anyway, yes just drop both front and rear and either replace with already completed diffs or have the ring and pinion gears changed. Replace all seals and check bearings too.

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Re: M1165A1 diff gear swap

Post by lkgindy » Mon Mar 08, 2021 5:03 am

You can buy new complete 2:73 diff’s and just drop your current units and replace them. That way you can keep your 3:08’s intact in case you ever want to put them back in.

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Re: M1165A1 diff gear swap

Post by Retired War Horses » Tue Mar 16, 2021 4:32 pm

Very well that your Torque converter switch on the brake pedal is staying locked up causing high RPM’s...check for a DTC 37 from the transmission
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ant929
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Re: M1165A1 diff gear swap

Post by ant929 » Wed Mar 24, 2021 9:33 am

I went through the trouble shooting in the TM and all tested good, and the Torque converter switch on the brake pedal is testing good. I also put in a new TCC Solenoid when I was changing the fluid. All the Ohms test where good. I jumped the two pins on the J1 plug and only got a continual 12, 12, 12, 12,12,12. I am at a loss.

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Re: M1165A1 diff gear swap

Post by Action » Wed Jun 30, 2021 7:47 am

Top speed of 60 mph in an m1165,,,,something is wrong. I would find out what the issue is instead of just changing diffs. What will a 2.73 vs 3.08 do, get you to 62 or 63 mph?
From memory, mine does 70 mph at 2700 rpm on flat road. It will go faster. that is just a reference point on rpm.
I think 50 mph was 2000 rpm.

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Re: M1165A1 diff gear swap

Post by Hell On Wheels » Sun Aug 08, 2021 9:52 am

I just finished a complete upgrade with my 1986 M998 converted to a M1026 to a 4L80E w/ Transfer and in the process both diffs 2.73 and went for a road test yesterday and hit 70 @2700 rpm but mid you I'm driving with a 6.2 v belt. When I run on flat surface I get those speeds but climbing hills it will slow down. Just like most military vehicles. I had that same issue when I was station both in Korea and Germany. which have some large hills.

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