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  #1  
Old 04-02-2008, 10:43 PM
ibcuda ibcuda is offline
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Confused rear axle ratio

Hello, just found my 8 1/4 rear end in the wrecking yard today but the tag is missing. Im having a hard time figuring out the ratio, dont you hold one axle and turn the other one while counting the turns on the yoke? It seems too be coming out to be approximently 1.3 to 1???? The casting numbers are 2852905 dont know if they mean anything. Picked it ip for $61.00 out of a 73 Duster seemed like a good deal. Any help would be greatly appreciated Thanx.
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Old 04-02-2008, 11:16 PM
dodger1 dodger1 is offline
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Thought it was the other way around - turn the yoke (driveshaft) and note the axle revs (don't hang onto either one when you do this)
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Old 04-02-2008, 11:41 PM
wilks3 wilks3 is offline
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Now take your 1.3 x 2 = 2.6 Thats your close rear gear ratio.
Open differential splits the gear ratio when one axle is held.
Remember, when doing a one tire burnout and speedo shows 60 MPH.....the tire is actually doing 120 MPH. Thats why the cross shaft and spider gears blow up alot.
Young and dumb, thinking its cool = wrecker ride home.....with Dads car.
He wasn't impressed. But I did learn how to swap a rear end.
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Old 04-03-2008, 03:05 AM
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dwc43 dwc43 is offline
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Just pull the rear cover off. The gear ratio is stamped on the ring gears outer edge.
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Old 04-03-2008, 10:44 AM
scredneck scredneck is offline
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I'm gonna go with dwc43 on this, seeing as how you got it from the salvage yard, it's always a good idea to change the fluids right off the bat anyway.
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Old 04-03-2008, 03:02 PM
John Kunkel John Kunkel is offline
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Turning the axle will get you a ballpark ratio but to know the exact ratio you have to know the ratios that were available in that rear end; in the case of the 8 1/4" the closest ratio to 2.6 is 2.71.
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Old 04-03-2008, 07:18 PM
valiant64 valiant64 is offline
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Ditto what dwc & scred said. Might wanna check out the pinion & axle seals as well...
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Old 04-03-2008, 08:01 PM
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Quote:
Originally Posted by wilks3 View Post
Remember, when doing a one tire burnout and speedo shows 60 MPH.....the tire is actually doing 120 MPH. Thats why the cross shaft and spider gears blow up alot.
The same thing happens in a front wheel drive, only it will blow much quicker since the pins are much smaller.

One of my sons took the transaxle out of a Toyota Camry from doing one-wheel spins in the snow one night. He was trying to impress his girlfriend. Yeah, she was impressed with me bitching him out all the way home after the wrecker dragged the car away.

The dealer called me a couple of days later, after tearing it down. The spider gears had cut right through the pins. The worst part of having that failure in a front wheel drive is that all the transmission components and the differential run in the same oil bath. All that powdered metal did a job on everything in the case. Cost me $2400 (20 years ago) for a used transaxle with no guarantee.

It was the last time he ever drove one of my vehicles.
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  #9  
Old 04-03-2008, 08:22 PM
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owatajrkiam owatajrkiam is offline
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It was the last time he ever drove one of my vehicles.[/QUOTE]

If that was my kid,...it would be the last time he DROVE his girlfriend......if ya' know what i mean!!!!!!!!!

Glen
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Old 04-03-2008, 11:39 PM
440roadrunner 440roadrunner is offline
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1. Lock one axle and see if you can turn the other. If not, you have a limited slip of some description

2. If you can turn one axle, turn it TWICE and simply count driveshaft revoloutions. This is more accurate than trying to multiply by 2 with less turns on the driveshaft

"I can top that story"

This was years ago when the first "full time" 4 x 4's came out. One weekend some of us got together and with us was an "outsider" whoed driven his almost new Jeep full time CJ up from over 200 miles away.

Now you have to compress this description in time--it all happened very fast. He climbed a small sand hill, and went storming over the top, the front end launching up in the air over the top. Because the sand was SO soft, and steep, he didn't quite have enough forward speed, and as soon as the front stopped pulling---because it was in the air!!-- the Jeep stalled for a split second--axle in the air, foot to the firewall, all the weight on the rear tires.

NOW--because of the full time unit--which is really a differential, the front driveshaft "tried" to go 2X "normal" speed, again, foot to the firewall. As the front end crashed down, one wheel hit first, which "shocked" the entire front end, as the OTHER WHEEL now "attempted" to go 2X the other wheel, which is a total of FOUR TIMES the normal speed.

An unGodly crunch came forth, and the entire front axle and transfer case instantly became junk.

He borrowed a trailer and went home. Of course Jeep would not fix it under warranty. This was of course a long time ago, and it seems to me the repair bill was over 3 thousand dollars, back then.
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  #11  
Old 04-04-2008, 09:26 AM
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Quote:
Originally Posted by valiant64 View Post
Ditto what dwc & scred said. Might wanna check out the pinion & axle seals as well...
I raise the hand on being number 4 for this.

And then change the rears gear oil now that you taken it all apart. It's probably never been changed. Now is a good time. Don't forget the additive for the suregrip rears.
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