Malamute wrote:
I haven't checked scads, but both Chevy and Fords that Ive checked and changed were one point off in diffs between front and rear. And yes, it loads up and pops loose when wound up on dry pavement. Its generally recommended not to have 4wd engaged on dry pavement, I always figured this was the reason, besides going around corners and winding it up between front and rear diffs.
Ok. This was bugging me, a lot (I have a huge ego and hate being wrong), so I went to a well known differential retailer that I and friends have bought R&P sets from using their gear charts and I figured out why I haven't run across this.
The short version is there are only a couple ratios that are different front and rear in Ford, Chevy and Jeep, and it depends on the axle models, and my experience for whatever reason has skipped over them. It is mostly a 4:11R/4:10F combo,
IF they are different models of axles.
For instance, it appears my F350 had Ford Sterling 10.25" 4:11 rear and Dana 60 4:10 front. I never had to service those beyond fluid as they were bombproof so I never had a reason to look at the tags. However, if it had a 3:73, 4:56 or 4:88 rear the front would also be the same exact ratio, in those axles. 3:55 rear would be 3:54 front. I have replaced or serviced 3:73 and 4:56 in that combo so my experience was they are the same.
My current F250 has the 10.5" Sterling rear and Dana 50 front, both are 3:73 ratio. If it had a 4:11 rear it would have a 4:10 front.
My 69 Jeep J2000 has Dana 44 axles front and rear and those are 4:11 front and rear. They are the same because they are the same model of axle.
I've had CJ's with Dana 44 rear/Dana 30 front axles, with 4:27, 3:73 and 3:55 ratios, those are the same front and rear, which matches my experience replacing several sets. If they had a 4:11 rear it would be a 4:10 front. Again the 4:11/4:10 anomaly.
I have had 1/2 ton Chevy trucks that were 4:11 front and rear (12bolt GM/D44 axles). I had a heavy 3/4 ton with 14 bolt rear/D60 front axles, in 3:73 front and rear that I lifted and installed 4:56 gears front and rear to run the larger tires. If I had used 4:11 rear it would have been 4:10 front.
So, it appears I was wrong and I was right, and that it was simply chance that in all the gear sets I have serviced or changed I did not run across this, or in the case of my F350, notice.
My apologies to Griff and thanks Malamute for the input and making me look.
Link to charts for gear ratios.
http://www.differentials.com/differenti ... pplication
"He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance." Declaration of Independance, July 4, 1776
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