I think I've read your technique before, even used it a couple times in the past as it was one I was taught by the transmission guy at the Pontiac Dealership I worked at when I got my Firebird.
New update! I just got back from a 3rd junkyard, guess I should have been patient. Found a '77 Seville there. I grabbed the front spindles, rotors and calipers. Then I went out back and grabbed the rear axle including the rotors and calipers! Whew, when I said pulling a rear axle by yourself isn't fun, adding the weight of two calipers and rotors make it even less fun :P At least there was no mud this time around, just gravel. So now there are TWO rear axles sitting in the back of the jeep. I'm disappointed I did not find a single '76-'79 X-body car with A/C though for the evaporator box.
OK, Cantvalve -
Posted this before but can't remember where so I'll do it again -
If open dif -
Hold one wheel
Turn the other wheel SLOWLY 10 times in the same direction (best to mark straight down so you know where you started)
Count the companion flange rotations. If it's - say - 26 and a third or so, it's a 2:73, 41 is a 4:10, etc.
If it is a limited slip it's a little easier:
Turn either wheel 10 times
Count the companion flange rotations and do the same math
If I had a dollar for every blah blah blah. We had to check all rear drive axle ratios at EPA to assure that the cars the MFGs brought us were what they were supposed to be.
Feel free to PM me as I don't want to hijack Randal's thread, but what is a companion flange? Also, is there any way to tell without pulling the rear cover? My car has an 8 in. Ford, so the rear cover thing doesn't apply to me.
Feel free to PM me as I don't want to hijack Randal's thread, but what is a companion flange? Also, is there any way to tell without pulling the rear cover? My car has an 8 in. Ford, so the rear cover thing doesn't apply to me.
Companion flange is the pinion yoke. Count the number of rotations of the pinion yoke. Another way I've used is cruise at a set rpm, like 2,000 or 3,000 in a 1:1 gear and see how fast you are going (either by acurate speedo or use a GPS) the go online and find a differential ratio calculator using rpm, speed and tire size. Even with a little converter slip it'll ball park you pretty close. The Cadillac one is just under 3.00:1, so I'm guessing a 2.73 or so. Didn't check the other diff yet.
Little clarification for the counting the turns method of checking the ratio. To check a posi, the axles will both turn the same direction and the same number of turns, so with both wheels off the ground, you can count the turns of the pinion to get one full revolution of either axle. With a non-posi, you need to make sure that you get two axle rotations in the same direction, the easiest way is to leave one wheel on the ground, and turn the other wheel two complete revolutions. The differential will magically make two revolutions of one axle into one revolution of the ring gear. Count the turns of the pinion to get the ratio.
I like Dan's suggestion of ten revolutions for greater accuracy, but it's usually sufficient to just use one turn of both axles (or two turns of one axle), and count the pinion turns as the ratio directly. But you do need to take up the freeplay in the rear before you start counting.
Good clarifications, Jim (as usual!). We did this so many times that I kind of do it automatically and really don't quite remember how I did it. If I dig out my old procedures manual I can probably find the step-by-step.
Some pictures of the Seville parts I pulled from the Junkyard last week. Sorry about the akward shots on the spindles. At first the spindles looked identical, but with a ruler I found were the extra clearance comes from. The coins highlight that.
Here is the spindle I've pulled off the Skylark. Notice the dime, it's the biggest coin I could fit in that spot.
Here is the Seville spindle, a quarter now fits where the dime was.
A stock rotor on my Skylark is on the right, the Seville one on the left.
And just because, a set of new front springs for a V-8 engine, so hopefully it'll lift the front end a bit from the V-6 springs that were in there.
I'll take pictures and such of the rear axle when I get around to removing it from the back of the Jeep. For now it is ballast for traction in the snow ;)
Got to do a little work around the house this morning. I pulled the calipers and rotors off the Seville axle, did a quick clean up job with the makita, and popped the diff cover off.
This is before I did the quick cleaning to it. I'm going to go over parts of it with a drill and wire brush to get into smaller areas. Then when the day is warm enough I'll simple green it down and hit it with a high pressure hose. (Yes, that is ice and snow scattered around)
The gear ratio I knew wouldn't be favorable, but it's really really unfavorable. The 16:41 tells me it's a 2.56 ratio, Blah :-\
Time to start pricing good axles, a carrier and gears.
Yeah, with the .64 Overdrive gear definately. But I'm sure I'll be limited to keep it under 125mph or so. The other rear end I grabbed had 2.41's in it :o I'll keep both around, you never know.
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