i know this is kinda stupid but - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crackajacka · 08-10-2003, 01:18 AM

how do u tell the gear ratio of a rear end?

77K20 · 08-10-2003, 02:57 AM

From what I have been told, and have read, the easiest way is to jack up the rear-end. Then make a mark at the top of the tire, and on the driveline. Rotate the tire 360* and count how many times the driveline turns.

i.e: Driveline makes barely past three rotations= 3.08
Driveline makes 3 1/2 rotations= 3.56
Driveline makes barely over 4 rotations= 4.10

You get the idea. Or you could also remove the differential cover and start counting teeth.

Someone correct me if I'm wrong, but this is what I have been told, and this is what I do.

2-Knee

p.s. make sure to block the front tires so your truck doesn't go anywhere.

jimfulco · 08-12-2003, 12:50 AM

That works on a posi, but on a peg-leg, jack up only one side, & turn the wheel TWO turns while you count the driveshaft revolutions. Both sides up on a peg-leg will give you a false reading. Not a bad idea to chock the front wheels before you do this.

Grey 87 · 08-13-2003, 11:18 PM

Pull your diff. cover off and count the teeth on the ring gear and the pinion gear. Divide the ring gear number by the pinion gear number and you will have your gear ratio.

ring gear =41
pinion gear=11

Your gear ratio will be 4.10

love it loud · 08-13-2003, 11:32 PM

41/11 is 3.73

Grey 87 · 08-13-2003, 11:34 PM

Quote:

Originally posted by Grey 87
Pull your diff. cover off and count the teeth on the ring gear and the pinion gear. Divide the ring gear number by the pinion gear number and you will have your gear ratio.

ring gear =41
pinion gear=11

Your gear ratio will be 3.73

Grey 87 · 08-13-2003, 11:36 PM

What a Maroon! Thanks for the correction.

**crossy** · 08-13-2003, 11:45 PM

If you don't feel like pulling the cover then use a file to clean off the top of the passenger side axle tube and you'll find a 3 letter code there. I know or can find most of them. 75% of 81-86's 2.73 ratio. DAVE

**swervin ervin** · 08-13-2003, 11:45 PM

From what I've read on all the parts catalogs I have, there is supposed to be a code stamped on the axle tube, about 3-6" out from the carrier, on the passenger side, front. I haven't looked at either of my trucks or van, but the catalogs give the ratios for the codes.

I need to check into this some more and see if I can find one. Anyway, if anyone does find a code, I have the books to tell you what it came with.

PHOENIX · 08-14-2003, 01:08 AM

I just went and looked at my rear axle. I didnt find any numbers on the tubes at all. But I did found the following on the pumpkin.
Passenger side:
GM32
Driver Side:
1254333
B43

Does that tell you anything?

**crossy** · 08-14-2003, 05:55 AM

remember that those numbers were stamped by humans so they could be off a little. I just went out and checked the 86 K5 I am parting out and they were right there.they tend to on the very top down to about the 2 o'clock position on the tube. my 3 letter code was first then all the part number rubbish that means other things. It's always there. like i said a file seems to work best for me . If it is grimey I use a putty knife. the only ones i have not been able to find it on are ones that are badly rusted.

On your 86 it will most likely start with an A,B, C or H and can havea number in there also.

Those numbers you found were part numbers for the center section and it's date. DAVE

messed up c-10 · 08-14-2003, 09:45 AM

Does your truck have a three speed or a four. You could probably find the factory specs. for an 86 from someone on the board. If your truck is mostly stock then I would guess that your gears are probably stock too. If you have a three speed I would bet that you have 2.73's if a four speed then maybe 2.73's or 3.08's.

LOHRTBT · 08-14-2003, 09:52 AM

Quote:

Originally posted by jimfulco
That works on a posi, but on a peg-leg, jack up only one side, & turn the wheel TWO turns while you count the driveshaft revolutions. Both sides up on a peg-leg will give you a false reading. Not a bad idea to chock the front wheels before you do this.

FINALLY!! Someone gave me the answer to the question I have asked everyone for the past 3 years!! haha Peg leg reading with both wheels up is crazy!! lol Thanks man!

PHOENIX · 08-14-2003, 12:06 PM

Are the numbers stamped into the tube or are the numbers raised?
I plan to open up the diff. cover pretty soon eitherway to check it out and change the gear oil (probably this weekend).

**swervin ervin** · 08-14-2003, 01:55 PM

I never knew these numbers existed until I started buying original GM Parts and Illustration catalogs. These things are great for helping to find part numbers and identifing parts for our trucks.

Anyway, I looked for the numbers on my van and couldn't find any. I checked the 85 and did find those. They are small, about 1/8" in size and like Dave said, they were stamped by hand. They used a die set to do it with so they are not deep at all. You have to look real close and have some bright light. Mine were about 6" out from the carrier, on the passenger side, almost dead center on the front of the tube.

The code on my 85 was BX3. This translates to:
2.73 ratio, 11.15 x 2.75 brakes, Exc. G80.

Happy searching.

Oh, if anyone finds their code and wants to know what it means, I'll be glad to look. Although I haven't looked at them in great detail, I have catalogs for all years of our trucks, even vans.

Mike

Prerunner1982 · 08-14-2003, 05:03 PM

i attempted to look but entire axle is covered in crap... so after some cleaning i will look again!

PHOENIX · 08-14-2003, 08:29 PM

Quote:

Originally posted by swervin ervin
Mine were about 6" out from the carrier, on the passenger side, almost dead center on the front of the tube.

I found them now.
I had to look a little closer.
TWA G040

**swervin ervin** · 08-14-2003, 09:34 PM

Eddie,

you are not going to believe this, but your truck falls into a catalog I don't have.

I have a 73-78 Parts catalog, 79-84 Illustration catalog, and 85-86 CK, 87-89 RV Parts and Illustration catalogs. But no 79-84 Parts catalog. I need to find the 73-78 Illustration catalog and 79-84 Parts catalog.

The Illustration catalogs don't have the codes, only the parts catalog. I found a 79-84 Parts catalog on ebay, but it is pretty ragged, so I think I'll pass on it.

http://cgi.ebay.com/ebaymotors/ws/eB...category=34216

Sorry, but I tried.

PHOENIX · 08-14-2003, 09:43 PM

Thats OK, anyone else have a book?

I will probably open the rear end this weekend anyway.

08-10-2003, 01:18 AM	#1
crackajacka Stylin Join Date: Sep 2001 Location: Tuttle, OK Posts: 620	i know this is kinda stupid but how do u tell the gear ratio of a rear end? __________________ Ive been traveling for some time, with my fishin pole and my bottle of shyne. Most Girls like finished products and just dont understand what a good addiction does for you http://www.paulwall.us/

08-13-2003, 11:32 PM	#5
love it loud Calibration Engineer Join Date: Oct 2002 Location: Windsor, Ontario, Canada Posts: 361	41/11 is 3.73 __________________ CANADIAN CONNECTION

08-13-2003, 11:36 PM	#7
Grey 87 Registered User Join Date: Aug 2003 Location: Texas Posts: 23	What a Maroon! Thanks for the correction. __________________ 87 SWB Silverado 84 LWB Custom Deluxe

08-13-2003, 11:45 PM	#8
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	If you don't feel like pulling the cover then use a file to clean off the top of the passenger side axle tube and you'll find a 3 letter code there. I know or can find most of them. 75% of 81-86's 2.73 ratio. DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

08-13-2003, 11:45 PM	#9
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	From what I've read on all the parts catalogs I have, there is supposed to be a code stamped on the axle tube, about 3-6" out from the carrier, on the passenger side, front. I haven't looked at either of my trucks or van, but the catalogs give the ratios for the codes. I need to check into this some more and see if I can find one. Anyway, if anyone does find a code, I have the books to tell you what it came with. __________________ Mike 1985 Chevy C-10

08-10-2003, 02:57 AM	#2
77K20 Registered User Join Date: Jun 2003 Location: Estacada, OR Posts: 37	From what I have been told, and have read, the easiest way is to jack up the rear-end. Then make a mark at the top of the tire, and on the driveline. Rotate the tire 360* and count how many times the driveline turns. i.e: Driveline makes barely past three rotations= 3.08 Driveline makes 3 1/2 rotations= 3.56 Driveline makes barely over 4 rotations= 4.10 You get the idea. Or you could also remove the differential cover and start counting teeth. Someone correct me if I'm wrong, but this is what I have been told, and this is what I do. 2-Knee p.s. make sure to block the front tires so your truck doesn't go anywhere.

08-12-2003, 12:50 AM	#3
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	That works on a posi, but on a peg-leg, jack up only one side, & turn the wheel TWO turns while you count the driveshaft revolutions. Both sides up on a peg-leg will give you a false reading. Not a bad idea to chock the front wheels before you do this.

08-13-2003, 11:18 PM	#4
Grey 87 Registered User Join Date: Aug 2003 Location: Texas Posts: 23	Pull your diff. cover off and count the teeth on the ring gear and the pinion gear. Divide the ring gear number by the pinion gear number and you will have your gear ratio. ring gear =41 pinion gear=11 Your gear ratio will be 4.10

08-14-2003, 01:08 AM	#10
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	I just went and looked at my rear axle. I didnt find any numbers on the tubes at all. But I did found the following on the pumpkin. Passenger side: GM32 Driver Side: 1254333 B43 Does that tell you anything? __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

08-14-2003, 05:55 AM	#11
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	remember that those numbers were stamped by humans so they could be off a little. I just went out and checked the 86 K5 I am parting out and they were right there.they tend to on the very top down to about the 2 o'clock position on the tube. my 3 letter code was first then all the part number rubbish that means other things. It's always there. like i said a file seems to work best for me . If it is grimey I use a putty knife. the only ones i have not been able to find it on are ones that are badly rusted. On your 86 it will most likely start with an A,B, C or H and can havea number in there also. Those numbers you found were part numbers for the center section and it's date. DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

08-14-2003, 09:45 AM	#12
messed up c-10 RHCP afficianado Join Date: Oct 2002 Location: McLoud, OK Posts: 789	Does your truck have a three speed or a four. You could probably find the factory specs. for an 86 from someone on the board. If your truck is mostly stock then I would guess that your gears are probably stock too. If you have a three speed I would bet that you have 2.73's if a four speed then maybe 2.73's or 3.08's. __________________ ~Ryan~ 89 S-10 Blazer with a 4.3L 96 Ford Crown Vic P71 4.6L V8. This car rocks. Here are some links to some good music. Jack Johnson Donavon Frankenreiter

08-14-2003, 12:06 PM	#14
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	Are the numbers stamped into the tube or are the numbers raised? I plan to open up the diff. cover pretty soon eitherway to check it out and change the gear oil (probably this weekend). __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

08-14-2003, 01:55 PM	#15
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I never knew these numbers existed until I started buying original GM Parts and Illustration catalogs. These things are great for helping to find part numbers and identifing parts for our trucks. Anyway, I looked for the numbers on my van and couldn't find any. I checked the 85 and did find those. They are small, about 1/8" in size and like Dave said, they were stamped by hand. They used a die set to do it with so they are not deep at all. You have to look real close and have some bright light. Mine were about 6" out from the carrier, on the passenger side, almost dead center on the front of the tube. The code on my 85 was BX3. This translates to: 2.73 ratio, 11.15 x 2.75 brakes, Exc. G80. Happy searching. Oh, if anyone finds their code and wants to know what it means, I'll be glad to look. Although I haven't looked at them in great detail, I have catalogs for all years of our trucks, even vans. Mike

08-14-2003, 05:03 PM	#16
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	i attempted to look but entire axle is covered in crap... so after some cleaning i will look again! __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

08-14-2003, 09:34 PM	#18
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Eddie, you are not going to believe this, but your truck falls into a catalog I don't have. I have a 73-78 Parts catalog, 79-84 Illustration catalog, and 85-86 CK, 87-89 RV Parts and Illustration catalogs. But no 79-84 Parts catalog. I need to find the 73-78 Illustration catalog and 79-84 Parts catalog. The Illustration catalogs don't have the codes, only the parts catalog. I found a 79-84 Parts catalog on ebay, but it is pretty ragged, so I think I'll pass on it. http://cgi.ebay.com/ebaymotors/ws/eB...category=34216 Sorry, but I tried.



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08-14-2003, 09:43 PM	#19
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	Thats OK, anyone else have a book? I will probably open the rear end this weekend anyway. __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

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