How many RPMs should a Humvee 1165 6.5 L turbo

[Tackelbarry]

with the 4L80E be turning at 55 mph, roughly? I test drove one that was between 3000-3500 at 55 and 60 mph. It seems like it took too long to shift and it might have a broken band in the trans or not going into overdrive. Thanks for your help.

 

[Mogman]

If it has the 400A alt it likely has an overdrive pulley so the RPM will show higher than it actually is, the turbo also has the highest ratio diffs at 3.07:1 so they do rev higher than the A2 trucks with the 4L80

 

[Tackelbarry]

I am completely new. Is there anything to insulate the floor and interior to reduce the engine and Road noise? There is no way my wife will ride in this thing as loud as it currently is.
I have not bought the truck yet, but am seriously considering buying it. Anything else to look at? Thanks again.

 

[Mullaney]

I am completely new. Is there anything to insulate the floor and interior to reduce the engine and Road noise? There is no way my wife will ride in this thing as loud as it currently is.
I have not bought the truck yet, but am seriously considering buying it. Anything else to look at? Thanks again.

.
Yes! There is plenty of sound deadening materials - some with "sticky back" that you can peel off and stick to the inside of the "doghouse". That will cut out a lot of noise from the engine. Then a little more under the seats and maybe a little in the bed of the truck as well. Spray bed liner will help insulate the sounds as well.

There are a ton of threads on sound proofing your vehicle...

 

[Tackelbarry]

.
Yes! There is plenty of sound deadening materials - some with "sticky back" that you can peel off and stick to the inside of the "doghouse". That will cut out a lot of noise from the engine. Then a little more under the seats and maybe a little in the bed of the truck as well. Spray bed liner will help insulate the sounds as well.

There are a ton of threads on sound proofing your vehicle...

like I said, completely new to this. Is the dog house the engine cover that attaches from the inside? Also, has anyone done a transmission swap to a 6L80E to reduce rpm’s for highway driving? Would it help and hold up?

 

[HoveringHMMWV]

with the 4L80E be turning at 55 mph, roughly? I test drove one that was between 3000-3500 at 55 and 60 mph. It seems like it took too long to shift and it might have a broken band in the trans or not going into overdrive. Thanks for your help.

3000-3500 seems way high at 55mph. My 1151A1, with a 200amp alt, is only running approximately 2100-2200 @ 55mph.

 

[Mogman]

like I said, completely new to this. Is the dog house the engine cover that attaches from the inside? Also, has anyone done a transmission swap to a 6L80E to reduce rpm’s for highway driving? Would it help and hold up?

I did, it is a much better transmission that the 4L80 as far as efficiency goes and is just a strong (hence the 80 rating)
It is allot of work and some of it is custom so not something you can get done "down the road" (or anywhere for that matter, you have to do the custom work yourself)
Here is the build thread

6L80 in my M998

EDIT, as you read this thread I ended up using a 6L80 as the 6L90 was toast and the 6L80 has the same output shaft as the 4L80/3L80. I was at a machine shop auction the other day and picked up a 6L90 with a MP1626XHD transfer case, it is complete with T/C, the front shaft, cooler lines and shift...

www.steelsoldiers.com

As far as I know I am the only one that has installed a 6L80, there was a company that claimed to be coming out with a "kit" but that never came to fruition again as far as I know.

 

[Mogman]

You are looking at around 4-5 grand without the custom machine work or install labor

 

[Coug]

If the truck is idling and the tach reads 900+ RPMs, then it's extremely likely that it has a 400 amp alternator with the small pulley, which makes the tach read about 36% higher than actual RPMs.

At 50mph a truck with 3.08 gearing (any of the turbo motor trucks, most obvious external feature is the front grill sticks out about 6" in front of the rest of the hood) will be turning around 2000 RPMs. These were also the trucks that came with the tachometer installed; most of the others it was added on later and less common to see.

With the 400 amp alternator and small pulley the tachometer will read around 3000 rpms, , which does seem close to what you were reporting of 3000-3500 at 55-60mph.

 

[Tackelbarry]

Has anyone tried a GPS or other style tach to get a correct reading? Thanks again.

 

[Mainsail]

Mine is the ECV with the turbo and 400 amp alternator- my idle RPM when warm is around 975RPM, which seems high and feels high (seems like it takes a bit of brake pedal pressure when stopped to stay stopped).

My M1009 CUCV would idle high, then once it got to temp there was a noticeable drop in RPM, such that you could easily hear the RPM drop. I don't notice that at all on the M1165, so I wonder if it's not dropping the RPM once warm.