whats the rear gear ratio?

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
My new Chevelle project has been a bit of a mystery. The guy I got it from either didn't really know what he had like he claims or just played dumb when I asked questions. There is melted rubber from doing burn outs on the quarter panels. When I asked him if he ever had slicks on the car he said he didn't know. He also played dumb when I asked what the rear gear ratio was but said it had a posi.

Tonight I jacked the rear of the car up both wheels off the ground. I didn't mark anything to get an exact number but I kept my hand on the tire in the same place turned it one revolution and watched the drive shaft yoke. One full turn of the tire the drive shaft made two revolutions.

After doing this I read something about needing to turn the wheel two revolutions not one. I figured a 2:1 one ratio seemed a little weird but I don't know.

Was I supposed to turn the tire two revolutions? If so that would give me about a 4.10 ratio that makes sense rather than a 2.10 ratio like I am hoping doesn't exist.



the best way is to pull the differential rear cover, inspect the condition of the ring & pinion gear and count the teeth, then divide the number of ring gear teeth by the number of pinion gear teeth, example,
lets say you had 8 pinion teeth and 34 ring gear teeth, 34/8=4.25 that would be a 4.25 :1 rear gear
33 ring gear 8 pinion gear, =4.125 gear ratio
9 pinion and 37 ring gear,=4.11:1
yes the rear differential gasket needs to be replaced and yes the differential gear lube will drain and need to be replaced , but you'll have taken the time and effort too visually inspect the differential internals and that may prevent expensive surprise repair issues, plus you have no idea as to the condition of the existing differential internals so inspecting that on a used car you think may have been run hard makes sense.
that and youll have replaced the gear oil of unknown volume and age thus the new clean gear oil may add significant additional durability , as the current lube may be low or years old, or contain dirt and debris

READ LINKS AND SUB LINKED INFO
http://garage.grumpysperformance.co...rence-in-top-end-with-4-10s.13581/#post-70170

c-clip are the stock or standard O.E.M. axle design, to get the conversion axles sold by several aftermarket suppliers youll want a matched set of
rear bearings and axles
https://www.strangeengineering.net/...kages-components-1/12-bolt-c-clip-eliminator/

https://www.strangeengineering.net/product/gm-pro-race-axles-elim-kit-1-2-stud-kit.html/

https://www.hotrod.com/articles/build-bulletproof-gm-10-bolt-axle-built-c-clip-eliminator/

http://www.moserengineering.com/faqs/

http://chassisengineering.com/index.php?route=product/category&path=4_104

https://www.summitracing.com/search/part-type/c-clip-eliminator-kits/axle-model/gm-8-5-in

https://www.markwilliams.com/c-clip...MI97f1u_Cz3QIVRbXACh2Xfw5yEAMYASAAEgL-SPD_BwE
related threads
http://garage.grumpysperformance.co...ears-differentials-available.1282/#post-36502

http://garage.grumpysperformance.co...ike-i-need-a-hole-in-my-head.4887/#post-13451

http://garage.grumpysperformance.com/index.php?threads/ok-youve-shreaded-your-10-bolt-rear.237/

performance rear differential axle/ differential parts manufacturers & related info

http://www.moserengineering.com/

https://www.strangeengineering.net/

https://www.markwilliams.com/axles....MIjdPBrO2z3QIVi7rACh38PgMhEAMYASAAEgKMsPD_BwE

https://www.currieenterprises.com/

https://www.mittlerbros.com/Automotive-Rear-Ends

https://www.motivegear.com/

https://dutchmanaxles.com/?SID=13e788c48f6972c9ebd5a6a2581b5139

http://www.differentials.com/

http://www.manciniracing.com/drivetrain-parts.html

https://www.hotrod.com/articles/hrdp-1009-bolt-in-rearend-buyers-guide/
 
Last edited:
Back
Top