I have the optional posi rear end what gears? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*vegaschevy* · 10-23-2009, 03:51 PM

Would like to figure out what gears are in my truck. I took my diff cover off to clean everything up, replace the oil and reseal the rear diff cover.

If I counted some of the teeth on the half can someone know what gearing it is?

any other easy ways to know?

71tahoe · 10-23-2009, 04:00 PM

The ratio is stamped somewhere on the ring gear. Otherwise you can count the teeth on the gear and divide by the number on the pinion.

should look like > 41:11 < this equals 3.73:1

69GMCLonghorn · 10-23-2009, 04:14 PM

There is also a formula to find out your gear ratio:

(RPM x Tire diameter)/(MPH x 336)

Just make sure your tach and speedo are calibrated first!

*Dylan · 10-23-2009, 04:23 PM

Or you can look on top of one of the axle tubes and there is a number stamped into the metal that will tell you. It's relatively close to the housing, I just can't recall what side it's on at the moment.

**LockDoc** · 10-23-2009, 04:34 PM

-
Here is a chart:

Rear Axle Ratios

Ratio 2.56:1 - Tooth Combination 41,16
Ratio 2.73:1 - Tooth Combination 41,15
Ratio 3.07:1 - Tooth Combination 43,14
Ratio 3.08:1 - Tooth Combination 40,13
Ratio 3.08:1 - Tooth Combination 37,12
Ratio 3.31:1 - Tooth Combination 43,13
Ratio 3.36:1 - Tooth Combination 37,11
Ratio 3.42:1 - Tooth Combination 41,12
Ratio 3.55:1 - Tooth Combination 39,11
Ratio 3.73:1 - Tooth Combination 41,11
Ratio 4.10:1 - Tooth Combination 41,10
Ratio 4.11:1 - Tooth Combination 37,9

LockDoc

**LockDoc** · 10-23-2009, 04:38 PM

Quote:

Originally Posted by *Dylan

Or you can look on top of one of the axle tubes and there is a number stamped into the metal that will tell you. It's relatively close to the housing, I just can't recall what side it's on at the moment.

The pics show where the code is located (it is actually the first two or three letters) and you can go here to look them up:

http://www.americanclassic.com/paint_test.asp

LockDoc

Longhorn Man · 10-23-2009, 05:20 PM

whats the original engine/trans combo, and what size is the truck?

*vegaschevy* · 10-23-2009, 05:46 PM

one more question, How much fluid goes in the rear diff? is it fill till it comes out or is there a specified amount?i

*vegaschevy* · 10-23-2009, 06:06 PM

also, does anyone put any sealant on the diff bolt? Mine was bone dry and not leaking but the flange does not bottom out as there is a red "posi" tag on the bolt.

**leddzepp** · 10-23-2009, 06:27 PM

Fill it until the fluid is even with the bottom of the filler hole. (Stick your finger in there and you can feel the fluid) I have a service manual, but it is not in front of me at the moment for the exact capacity. I do not use sealant on the diff cover bolts, but I dont think it would hurt if you did. Torque them to 7 lbs....over tightening them will cause leaks. I just did this on both of my trucks in the past few weeks. I drove the SWB on a 12 hr trip, and NO drips, leaks etc. I use Gasgacinch on both sides of a Fel-pro gasket. I also lightly sanded the mounting surfaces prior to installing the gasket.

Make sure you use limited slip gear oil, since you have posi.

**leddzepp** · 10-23-2009, 06:32 PM

If you want to figure out the gear ratio, jack up the truck. Pull one of your tires off. Put a lug nut on one of the lugs (for reference) Put it in the 12 o clock position (make sure tranny is in neutral) Now turn your driveshaft and count the number of turns it takes to get that lug back to the 12 o clock position. I also just did this on my project truck It took 3 3/4 turns for me, so I have a 3.73 rear end ratio. Very easy way to do it.

**leddzepp** · 10-23-2009, 06:50 PM

While you have the diff cover off, why not replace the axle seals and the pinion yoke seal at the same time? It's easy to do, and now is the time to do it. Click on my build link to see pics, I just got done doing all of this stuff.

*vegaschevy* · 10-23-2009, 06:53 PM

Well i finished up before my responses. I filled to the bottom of the holes, and used no sealant on the fill bolt.

used just under 2 quarts this way.

**leddzepp** · 10-23-2009, 07:17 PM

You should be good to go! Are you sure you have posi? An easy way to tell is jack the truck up, spin both tires. They should go in the same direction if you have posi.

*vegaschevy* · 10-23-2009, 07:24 PM

Quote:

Originally Posted by leddzepp

You should be good to go! Are you sure you have posi? An easy way to tell is jack the truck up, spin both tires. They should go in the same direction if you have posi.

yep positive i have posi.. lol

**leddzepp** · 10-23-2009, 07:26 PM

I was going to say that, but you beat me to it

unclewatts · 10-24-2009, 04:25 AM

Quote:

Originally Posted by vegaschevy

yep positive i have posi.. lol

Did you remember to add the limited slip additive?

*vegaschevy* · 10-24-2009, 12:12 PM

Quote:

Originally Posted by unclewatts

Did you remember to add the limited slip additive?

yes sir

10-23-2009, 03:51 PM	#1
vegaschevy Account Suspended Join Date: May 2009 Location: las vegas nv Posts: 1,493	I have the optional posi rear end what gears? Would like to figure out what gears are in my truck. I took my diff cover off to clean everything up, replace the oil and reseal the rear diff cover. If I counted some of the teeth on the half can someone know what gearing it is? any other easy ways to know?

10-23-2009, 04:00 PM	#2
71tahoe Registered User Join Date: May 2006 Location: Jonesboro, AR Posts: 916	Re: I have the optional posi rear end what gears? The ratio is stamped somewhere on the ring gear. Otherwise you can count the teeth on the gear and divide by the number on the pinion. should look like > 41:11 < this equals 3.73:1

10-23-2009, 04:14 PM	#3
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: I have the optional posi rear end what gears? There is also a formula to find out your gear ratio: (RPM x Tire diameter)/(MPH x 336) Just make sure your tach and speedo are calibrated first!

10-23-2009, 04:23 PM	#4
*Dylan Mean Buzzin' Half Dozen Join Date: Mar 2008 Location: Orlando, Florida Posts: 1,081	Re: I have the optional posi rear end what gears? Or you can look on top of one of the axle tubes and there is a number stamped into the metal that will tell you. It's relatively close to the housing, I just can't recall what side it's on at the moment. __________________ "War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." MY TRUCK (Now for sale) 1967 C10 SWB *Dylan* IIMY?

10-23-2009, 04:34 PM	#5
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,465	Re: I have the optional posi rear end what gears? - Here is a chart: Rear Axle Ratios Ratio 2.56:1 - Tooth Combination 41,16 Ratio 2.73:1 - Tooth Combination 41,15 Ratio 3.07:1 - Tooth Combination 43,14 Ratio 3.08:1 - Tooth Combination 40,13 Ratio 3.08:1 - Tooth Combination 37,12 Ratio 3.31:1 - Tooth Combination 43,13 Ratio 3.36:1 - Tooth Combination 37,11 Ratio 3.42:1 - Tooth Combination 41,12 Ratio 3.55:1 - Tooth Combination 39,11 Ratio 3.73:1 - Tooth Combination 41,11 Ratio 4.10:1 - Tooth Combination 41,10 Ratio 4.11:1 - Tooth Combination 37,9 LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

10-23-2009, 05:20 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: I have the optional posi rear end what gears? whats the original engine/trans combo, and what size is the truck?

10-23-2009, 05:46 PM	#8
vegaschevy Account Suspended Join Date: May 2009 Location: las vegas nv Posts: 1,493	Re: I have the optional posi rear end what gears? one more question, How much fluid goes in the rear diff? is it fill till it comes out or is there a specified amount?i

10-23-2009, 06:06 PM	#9
vegaschevy Account Suspended Join Date: May 2009 Location: las vegas nv Posts: 1,493	Re: I have the optional posi rear end what gears? also, does anyone put any sealant on the diff bolt? Mine was bone dry and not leaking but the flange does not bottom out as there is a red "posi" tag on the bolt.

10-23-2009, 06:27 PM	#10
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: I have the optional posi rear end what gears? Fill it until the fluid is even with the bottom of the filler hole. (Stick your finger in there and you can feel the fluid) I have a service manual, but it is not in front of me at the moment for the exact capacity. I do not use sealant on the diff cover bolts, but I dont think it would hurt if you did. Torque them to 7 lbs....over tightening them will cause leaks. I just did this on both of my trucks in the past few weeks. I drove the SWB on a 12 hr trip, and NO drips, leaks etc. I use Gasgacinch on both sides of a Fel-pro gasket. I also lightly sanded the mounting surfaces prior to installing the gasket. Make sure you use limited slip gear oil, since you have posi. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man Last edited by leddzepp; 10-23-2009 at 06:29 PM.

10-23-2009, 06:32 PM	#11
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: I have the optional posi rear end what gears? If you want to figure out the gear ratio, jack up the truck. Pull one of your tires off. Put a lug nut on one of the lugs (for reference) Put it in the 12 o clock position (make sure tranny is in neutral) Now turn your driveshaft and count the number of turns it takes to get that lug back to the 12 o clock position. I also just did this on my project truck It took 3 3/4 turns for me, so I have a 3.73 rear end ratio. Very easy way to do it. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man Last edited by leddzepp; 10-23-2009 at 06:33 PM.

10-23-2009, 06:50 PM	#12
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: I have the optional posi rear end what gears? While you have the diff cover off, why not replace the axle seals and the pinion yoke seal at the same time? It's easy to do, and now is the time to do it. Click on my build link to see pics, I just got done doing all of this stuff. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man

10-23-2009, 06:53 PM	#13
vegaschevy Account Suspended Join Date: May 2009 Location: las vegas nv Posts: 1,493	Re: I have the optional posi rear end what gears? Well i finished up before my responses. I filled to the bottom of the holes, and used no sealant on the fill bolt. used just under 2 quarts this way.

10-23-2009, 07:17 PM	#14
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: I have the optional posi rear end what gears? You should be good to go! Are you sure you have posi? An easy way to tell is jack the truck up, spin both tires. They should go in the same direction if you have posi. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man Last edited by leddzepp; 10-23-2009 at 07:18 PM.

10-23-2009, 07:26 PM	#16
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: I have the optional posi rear end what gears? I was going to say that, but you beat me to it __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man



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