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6.2 owners:
- Thread starter colbystephens
- Start date
Well, with Russel's set-up the engine was turning at 1900 rpm at 65 in 4th...in a heavy truck with a camper. Drop it in 5th and the rpm's would drop to 1400 rpm and I'm sure it'd fall on it's face.
Tires, gearing and tranny all have to be within certain ranges for it to work well. Ideal is if you drop it into 5th and it'll pull 1850-2000 rpm at 65 mph with whatever tires you are running. If you need a bit more power at highway speeds you can gear it a bit more aggressively.
Russel's rig would have been much happier with 4.56's...
Rene
Tires, gearing and tranny all have to be within certain ranges for it to work well. Ideal is if you drop it into 5th and it'll pull 1850-2000 rpm at 65 mph with whatever tires you are running. If you need a bit more power at highway speeds you can gear it a bit more aggressively.
Russel's rig would have been much happier with 4.56's...
Rene
Yup, really poor gearing in that truck. I later stepped it up to 4.56 and it was definitely much peppier, I could go much faster than the speed limit in 5th gear.
DieselWarrior
1/2 ton status
To bump off what rusty was saying, the engine RPM, for diesel or gas both... have a "sweet range" of RPMs, we call them the power band, the lower most and highest RPM that maximum POWER is produced. Tires, diffs, transfer case and transmissions all play a factor in what the RPM is going to be for an engine at a given SPEED (MPH).
If the engine is within the power band in 4th gear at 55 mph, for example... switching to 5th gear would reduce the effective horsepower produced by the engine, thus climbing a hill in 5th would not be practical.
Another factor that would play into the whole scene, is... the amount of weight that that horsepower needs to move.
For example, just pulling numbers out of the sky, if you had 100 lbs per 1 HP of power, you would be in good shape. (This is just for discussion, reality dictates different numbers). If you load your vehicle up with cinder blocks and tree trunks, you may now may have 400 lbs per 1 HP of power. Reduction in gearing is needed to be able to move that much weight, thus effectively "multiplying the amount of power at the wheels".
Theres more to it, and Im sure someone with more knowledge can expand on it.
HTH,
Andrew
If the engine is within the power band in 4th gear at 55 mph, for example... switching to 5th gear would reduce the effective horsepower produced by the engine, thus climbing a hill in 5th would not be practical.
Another factor that would play into the whole scene, is... the amount of weight that that horsepower needs to move.
For example, just pulling numbers out of the sky, if you had 100 lbs per 1 HP of power, you would be in good shape. (This is just for discussion, reality dictates different numbers). If you load your vehicle up with cinder blocks and tree trunks, you may now may have 400 lbs per 1 HP of power. Reduction in gearing is needed to be able to move that much weight, thus effectively "multiplying the amount of power at the wheels".
Theres more to it, and Im sure someone with more knowledge can expand on it.
HTH,
Andrew
DieselWarrior
1/2 ton status
Downhill, yeah. :-)
The NA 6.2L Detroit Diesel is a great engine, but it is not a mega power house. It was primarily designed for economy, according to many reads. Being that the M1009 has 3.08 gears, 4th gear with no larger than Id guess 33 inch tires would be a "good setup". Typically these trucks came with only a 3 speed trans, for a good reason... they were called on to haul a lot more weight on a regular basis than the Civi model.
M1009 w/3.08 reference:
http://www.steelsoldiers.com/cucv/32699-m1009-gears-recovery-question.html
Im anxious for someone to come in and either correct me or add to the knowledge bank.
Andrew
DieselWarrior
1/2 ton status
http://coloradok5.com/forums/showthread.php?p=1154
This says 4.10/11. Id go with that more, since from previous experience driving the CUCV in the Army, they did tend to wind tight at 55mph, and seamed to have more "power" than my civi K5.
Andrew
This says 4.10/11. Id go with that more, since from previous experience driving the CUCV in the Army, they did tend to wind tight at 55mph, and seamed to have more "power" than my civi K5.
Andrew
