Something doesn't quite make sense. I have 5.9L Dakota 2wd, auto with the
3.92 rear axle. I'm running the stock 255/65R15's and at 60 MPH it tachs at
3000 rpm with O/D locked out. By my calculation, if I were to put your tires
on my Dak, I'd drop the RPM's down to around 2563 at that speed. That would
be equivalent to 70 MPH at 3000 RPM. Now, I can't think of anything else
that's different between your drivetrain and mine that would affect RPM's vs
MPH so unless I'm missing something obvious one or both of our speedometers
must be off. I think I'll break out the GPS and get an accurate speed
measurement.
Regards, Mike Klinke
-----Original Message-----
From: Mike Adair <spinlocker@yahoo.com>
To: dakota-truck@buffnet.net <dakota-truck@buffnet.net>
Date: Saturday, October 21, 2000 11:40 PM
Subject: DML: Re; Anybody have any problems w/ 3.90 axle w/ V8 5 spd
>>I have a 98 club cab with 5.2 v8 5spd 3.90 axle
>ratio. I am having
>doubts
>>about the 3.90 axle ratio. I have had Transmission,
>Transfer case and
>axle
>>problems. I am thinking I should replace 3.90 with
>the standard 3.55
>ratio.
>>
>>Thank y
>
>I have a 96 CC 1500 Ram w/ 5.9 auto. Running
>285/75x16s. I went from a 3.55 open to a 3.92 posi, as
>the power increase from the supercharger warranted
>same.
>
>What worked super for hot rodding wasn't worth squat
>for towing. 3000rpm@64mph in direct, 2000@70mph in
>o/d. The engine pulls sweetly in the 2400-2700rpm
>range. So what's a boy to do? Slow down in direct, or
>push it in o/d (gets into boost, kills gas mileage to
>boot)?
>
>Based on heat and trannys weakness, I would rather
>pull in direct. Do to so would require me to go back
>to the 3.55 rear. I would loose that off the line jump
>of the 3.92s, however.
>
>Or, I could go to a low profile tire. My math yields
>255/70s or 295/60s, allowing me to pull in o/d
>65-70mph, 2400-2800rpm. But, it's o/d, wouldn't that
>cause a heat buildup? I'm running a B&M 16000# tranny
>cooler, btw.
>
>Mike
>Dallas, Tx
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