Ways to tell gear ratio
#1
Ways to tell gear ratio
I have a few reasons to believe my truck has been gear swapped. I've asked Ford what gears it came with, they say 3.73. The rear diff says 73ls on it. However, the way it runs compared to my old excursion is huge. I thought mostly that was due to the weight difference, but the RPMs seem a bit different than what I remember; so I decided to check it out.
According to Engine RPM Calculator (and other calculators) with 0.71 od ratio, 65mph, 32 inch tires (it does have 33s but the speedo has not been calibrated for that) and 4.30 gears, it looks like the rpms are supposed to be 2084, which looks right. At 75mph (didn't take a pic), it's just under 2500 rpm, which also comes out...
My question is, is there any foolproof way I can tell the gears? Anything I can read/datalog with the sct x3 programmer? Or for those of you using torque android app, any way I can read any PID or anything? Or can i just make a calculation between obd2 mph, trans gear ratio and rpm?
Any other ways I can tell with a certainty what gears I have in the truck?
According to Engine RPM Calculator (and other calculators) with 0.71 od ratio, 65mph, 32 inch tires (it does have 33s but the speedo has not been calibrated for that) and 4.30 gears, it looks like the rpms are supposed to be 2084, which looks right. At 75mph (didn't take a pic), it's just under 2500 rpm, which also comes out...
My question is, is there any foolproof way I can tell the gears? Anything I can read/datalog with the sct x3 programmer? Or for those of you using torque android app, any way I can read any PID or anything? Or can i just make a calculation between obd2 mph, trans gear ratio and rpm?
Any other ways I can tell with a certainty what gears I have in the truck?
#4
#6
it won't be perfectly round with all the weight on it; and the thread adds a bit of diameter/radius variation between new and well worn...
#7
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#9
My tires look like they should be on a fricken 2wd ranger. Theyre so small for my truck.
#10
I have 315/75/16 (34.7") tall, with a 2.8" levelling kit, I did have to space out my bumper 5/8" and pull the inner fender wells back at the rear of the well and secure with cable ties, but no rubbing now. Every truck will be a little different, I'm also running 10" wide wheels which was the main reason for bumper spacing. With my stock wheels and 305's I had no rubbing.
#11
I have a few reasons to believe my truck has been gear swapped. I've asked Ford what gears it came with, they say 3.73. The rear diff says 73ls on it. However, the way it runs compared to my old excursion is huge. I thought mostly that was due to the weight difference, but the RPMs seem a bit different than what I remember; so I decided to check it out.
According to Engine RPM Calculator (and other calculators) with 0.71 od ratio, 65mph, 32 inch tires (it does have 33s but the speedo has not been calibrated for that) and 4.30 gears, it looks like the rpms are supposed to be 2084, which looks right. At 75mph (didn't take a pic), it's just under 2500 rpm, which also comes out...
My question is, is there any foolproof way I can tell the gears? Anything I can read/datalog with the sct x3 programmer? Or for those of you using torque android app, any way I can read any PID or anything? Or can i just make a calculation between obd2 mph, trans gear ratio and rpm?
Any other ways I can tell with a certainty what gears I have in the truck?
According to Engine RPM Calculator (and other calculators) with 0.71 od ratio, 65mph, 32 inch tires (it does have 33s but the speedo has not been calibrated for that) and 4.30 gears, it looks like the rpms are supposed to be 2084, which looks right. At 75mph (didn't take a pic), it's just under 2500 rpm, which also comes out...
My question is, is there any foolproof way I can tell the gears? Anything I can read/datalog with the sct x3 programmer? Or for those of you using torque android app, any way I can read any PID or anything? Or can i just make a calculation between obd2 mph, trans gear ratio and rpm?
Any other ways I can tell with a certainty what gears I have in the truck?
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