***-End Dilemma

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Captainkirk said:
Pretty sure they are both Sure Grips. Is there an ID that confirms it?
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I don't think so unless it has a "Use sure grip lube" tag on it.

sure grip lube tag.jpg
 
And just for "what it's worth", the wear on the rears that you list isn't as clear cut as the mileage makes it sound- in your case, the revolutions per mile of a 3.91 (and therefore wear) versus say, a 3.23 brings the total revolutions turned in their respective time frames a bit closer together, not to mention that since the 3.91 is spinning faster at a given ground speed, it will operate at a somewhat (but perhaps negligible) higher temperature, also possibly contributing to wear... In that light, as long as they both are in solid shape, I wouldn't let the mileage be a deciding factor in your decision at all. But I'm probably just making a mountain out of a molehill anyways.
Back to my coffee. I'm still not totally awake.
 
Professor Fate said:
And just for "what it's worth", the wear on the rears that you list isn't as clear cut as the mileage makes it sound- in your case, the revolutions per mile of a 3.91 (and therefore wear) versus say, a 3.23 brings the total revolutions turned in their respective time frames a bit closer together, not to mention that since the 3.91 is spinning faster at a given ground speed, it will operate at a somewhat (but perhaps negligible) higher temperature, also possibly contributing to wear... In that light, as long as they both are in solid shape, I wouldn't let the mileage be a deciding factor in your decision at all. But I'm probably just making a mountain out of a molehill anyways.
Back to my coffee. I'm still not totally awake.
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Good point...and one I hadn't thought of. Thanks!
 
If either center section is out of the housing, all you have to do is look, there are lots of pics here to tell you what a clutch sg, cone sg, and open look like.
If they are both in a housing, turn the rear end yoke. With a sure grip, both wheels/axles turn the same direction. If its open, one wheel will turn one direction, the other either wont turn, or it will turn the opposite direction .
 
33IMP said:
If either center section is out of the housing, all you have to do is look, there are lots of pics here to tell you what a clutch sg, cone sg, and open look like.
If they are both in a housing, turn the rear end yoke. With a sure grip, both wheels/axles turn the same direction. If its open, one wheel will turn one direction, the other either wont turn, or it will turn the opposite direction .
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Rear end(s) are out of the car, but not opened up. I will check using this method tonight and post results here.
 
toolmanmike said:
Going to save that one. It works pretty slick. Thanks for sharing.
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At one time, it had the option of choosing from transmissions on a drop down list. I added in the white and red stripe Hemi ratio sets and several other Chrysler car and truck transmissions. I haven’t seen that on there on some time. I don’t know if it got deleted or if it’s in a section I’ve not seen lately.
If you want to type in something interesting for entertainment, the farthest extreme I’ve used it for an eighth mile racing and setting a start line ratio of 14 to 16.5:1 and 8450 rpm shift points with a four speed with custom ratios. Now if they could just add in drag racing simulator that you could add in the weight and hp, we’d really have something.
 
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Yeah, definitely a bust on the street. But a different matter altogether on a prepped track with an adequately sized drag slick when running in the eighth. And even then, it’s more for short stroke high rpm builds. But it’s really impressive impressive in that type of thing.
 
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Captainkirk said:
Rear end(s) are out of the car, but not opened up. I will check using this method tonight and post results here.
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The one is definitely an 8-3/4 Sure Grip and 3.55 gears. One full rotation of the wheels is 3 and a half turns of the chunk. Both wheels turn in the same direction.
 
If that is the original center section, its probably a 489 case with the big pinion, and a cone sg. 3.55 is an excellent compromise ratio, not crazy rpm on the highway, but good off-the line compared to 3.23. That was an optional acceleration gear.
Edit: rpm at 70 mph with 5%converter slip....
3.91 w 26"tires. 3715
3.91 w 28" 3450
3.55 w 26" 3373
3.55 w 28" 3132
So, approx 250 rpm for 2"taller tire. A 3.55 with a short tire is almost the same as a 3.91 with a tall one.
2nd edit: oops, forgot you had a four speed, will recalculate.
Wallace says subtract around 150 rpm, comparing a 0%clutch slip to a 5%slip converter.
 
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The other rear end is also Sure Grip, almost 4 revolutions to 1 so we're going with 3.91 as I originally suspected on that one. That's a lot of gear for a 4-speed.
 
Captainkirk said:
That's a lot of gear for a 4-speed.
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but a nice city gear, works very well with a 220/230 cam; 3.91 x 1.92=7.51

IMO, for an A833 equipped street-car,
a nice Second road-gear ratio is about 7.2 to 7.5 with 27s; on account of top of Second gear is 60=5340/5600 with 27s. So that should work slick with about a 224/230* cam, not still spinning the tires,lol.
I run 8.55/1 with a 230cam, and it's a bit high on account of 60=6370. But that is in first-over. In 1.92 second the ratio is 6.82/1, and 60=5100.. Therefore my combo is only sorta optimized for city, but that makes no never mind on account of in either ratio, the tires are still spinning at WOT. I tried running three ratios to 60, but that was a bust.
My combo is optimized for 93mph in the Eighth, as 93=6140 by the math, in Second-over. Hyup one pull on the stick, and two electric shifts of the GVod. Bang! bang! bang! I quit fooling around with gears after that.
 
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