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Post by jims442 on Dec 27, 2012 9:27:05 GMT -5
i want to put a possi unit in my car doesn't have possi now its a automatic with a 350 tranny don't know what kind of gears i have but i tach about 4000 at 65 i would kind of like more of a cruiseing gear but i would also like to smoke the tires once in awhile i had read on a post that you can't put a possi unit in a non possi rear end or should i try to find a possi rear end out of a 65 olds or what else will fit with the same length i guess i'm just looking for some help and input thanks
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Post by shane on Dec 27, 2012 11:09:09 GMT -5
What's your experience on rear ends? And 4000 rpms at 65 mph seems awful high for a peg leg . I would open it up so I know exactly what I have.
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Post by Big Mike on Dec 28, 2012 9:49:21 GMT -5
I'm with Shane, 4000 rpm's at 65 is a really high ratio for a peg leg rear end. I don't know what tire size you have, but putting the basic info in the many online calculators out there and I can't get a mph of 65, they are all way higher. You could have a high ratio posi rear with a bad posi unit, say maybe 3.73 or higher maybe. I'd open it up and take a look as well.
Your trans has a 1:1 final ratio so it's not the trans unless you have an incompatibility with the trans speedo gear and an original speedo gear or a reducer on the speedo cable?
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Post by Deleted on Dec 28, 2012 11:04:39 GMT -5
I remember going thru this awhile back, someone posted with a wildly high rpm @ "X" MPH. After several posts on possible causes, I don`t remember the OP ever coming back to tell us all what the culprit ended up being. But I will agree mike, the #`s are off the chart(for ANY rear gears). I`d also suggest the OP do some investigating, come back after the obvious is discounted.
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Post by jims442 on Dec 28, 2012 21:41:31 GMT -5
thanks for all the input i'm going to open it up this weekend and i'll post my findings
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Post by jims442 on Dec 28, 2012 21:42:45 GMT -5
my tires are 14
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Post by jims442 on Dec 30, 2012 12:13:58 GMT -5
heres what it looks like now what, i don't know much on rear ends
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Post by Big Mike on Dec 30, 2012 16:49:57 GMT -5
heres what it looks like now what, i don't know much on rear ends Nope, that's not a posi for sure. My guess would be you have an incapatable trans speedo gear ring on the output shaft. Speedo gears come in sets, one for the trans output shaft, one for the speedo cable. If they don't match, god knows what MPH to RPM you will get.
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Post by jims442 on Dec 30, 2012 17:15:09 GMT -5
how do i figure out what gears i have somewhere down the line i took the # off the casing and on bro's sight i think it said i have 353s gear or something like that
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Post by tp on Dec 30, 2012 18:12:35 GMT -5
you can change that peg leg out for aposi unit i've changed out a 3.23 peg leg to a 3.55 posi and i think mike 's right about speedo gears at 4000 rpm it would sound like that you r eng would be screamin a littlebit
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Post by shane on Dec 30, 2012 18:23:25 GMT -5
Look at your ring gear. There should be a number stamped on it my ring gear has 39/9 . Take the first number and divide it by the second number . 39 divided by 9 would equal 4.33
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Post by Big Mike on Dec 30, 2012 18:25:10 GMT -5
I can't seem to find anything tonight. Somewhere[/u], I have a chart that reads like this;
Trans Gear - color = White - Teeth = 32 Speedo Gear - color = Red - Teeth = 18 Gear Ratio = 4:10 rear
Meaning that a white trans gear with 32 teeth with a red speedo gear with 18 teeth was the proper gear set for a 4:10 rear. This chart was/is for GM cars only.
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Post by mongoose on Dec 31, 2012 12:42:05 GMT -5
If you've got a smart phone you can download an app that will show you your speed, and you can compare that to your speedometer reading to see how close/far off the reading is.
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Post by Deleted on Dec 31, 2012 13:20:03 GMT -5
Just borrow someones Garmin, or Tom Tom, throw it on your dash & go for a ride. There extremely accurate
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Post by jims442 on Dec 31, 2012 18:13:17 GMT -5
the# stamped on my gear there is 2 of them 42-13 gm 12-64 what does that mean?
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Post by hurstoldz on Dec 31, 2012 18:27:00 GMT -5
42 divided by 13 = 3.23
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Post by hurstoldz on Dec 31, 2012 18:28:12 GMT -5
12 -64 ***might*** be the date, but you have 3:23 gears
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Post by jims442 on Jan 1, 2013 13:32:15 GMT -5
took it out today seems i was wrong at 65 i'm tacking 3200 which i think is ok i'm still going to look for a possi unit and change my gear set up thanks everyone for all your input also happy new year
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Post by Deleted on Jan 4, 2013 2:21:18 GMT -5
Hey look who's here. Had 3.55's in the red car, the bolted in a 3.73 from a '71. Then she danced around town, not a highway car. Happy New Year Buon Anno!
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Post by oldsproject on Jan 4, 2013 21:00:13 GMT -5
Put 3:73s in mine and love them! Will eventually add OD so thats why i did it but fun as hell
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