Diff questions
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From: Saskatchewan
Diff questions
I've got a 94 F-350 turbo diesel (IDI), 5 speed with DRW. Rear wheel drive.
At 100 kph on the speedo, in overdrive, the rev indicator shows 2400 RPM.
What is my rear ratio?
Are the DRW diffs limited slip?
At 100 kph on the speedo, in overdrive, the rev indicator shows 2400 RPM.
What is my rear ratio?
Are the DRW diffs limited slip?
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Joined: Apr 2004
Posts: 34,472
Likes: 2,799
What is your tire size?
If you have 235/85x16, you have a 32" diameter.
At 100 kmh, (62 mph used in the calculator), 32 inch tires, a .76 ratio in your OD 5th gear, your rear axle would have to be 4.88 to make you run 2414 rpm.
If you have 215/85x16 tires, you have a 30" tire.
At 100 kmh, using all the same other info, you would need a 4.56 ratio to run 2406 rpm.
I found these tire sizes using Tire Rack's info, so if you have different tires, find out the diameter and plug your numbers in here:
http://www.novak-adapt.com/knowledge/gearing.htm
Not all DRW axles are limited slip.
The factory put a tag on your axle, probably on one of the bolts holding the cover on it. If you have a tag, and can post all the numbers in order, it can be decoded. There is also an axle code on your data plate/tire-gvwr plate on the door jamb. If your axle is OEM, that code will tell the tale also.
If you have 235/85x16, you have a 32" diameter.
At 100 kmh, (62 mph used in the calculator), 32 inch tires, a .76 ratio in your OD 5th gear, your rear axle would have to be 4.88 to make you run 2414 rpm.
If you have 215/85x16 tires, you have a 30" tire.
At 100 kmh, using all the same other info, you would need a 4.56 ratio to run 2406 rpm.
I found these tire sizes using Tire Rack's info, so if you have different tires, find out the diameter and plug your numbers in here:
http://www.novak-adapt.com/knowledge/gearing.htm
Not all DRW axles are limited slip.
The factory put a tag on your axle, probably on one of the bolts holding the cover on it. If you have a tag, and can post all the numbers in order, it can be decoded. There is also an axle code on your data plate/tire-gvwr plate on the door jamb. If your axle is OEM, that code will tell the tale also.
