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Jul 21st, 2025 | | | | Joined: Mar 2006 Posts: 77 Wrench Fetcher | | Wrench Fetcher Joined: Mar 2006 Posts: 77 | Ok... I've read about counting the teeth in a rearend to tell the ratio, but I have no idea how to go about telling the ratio by counting the teeth. So, could someone here tell me that?
I obtained a '61 rearend today, but it's only the housing and the center gears. No axle shafts or brake drums.
Anyway, I would like to know the ratio.
Thanks very much!! | | | | | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | Robbie,
I'm math challenged, but I think if you divide the large number..the ring gear count by the small number, the pinion count, you will get the ratio of the rear end. Give it a try!
Stuart
| | | | | Joined: Nov 2005 Posts: 6,061 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,061 | Hy RobbieWright, a ratio is the relationship between two gears, in the case of a differential, it is the relationship between the pinion gear [ input at driveshaft ] and the crown gear [ output connected to axles ] if the pinion has 6 teeth and the crown has 36 teeth, divide the pinion number into the crown number in this case 6 into 36 equals a 6:1 ratio, hope that helps. | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | If you can get the code numbers off the face of the 3rd member, I can decode them for you. Stuarts method would be correct if you count the teeth.
Bill Burmeister
| | | | | Joined: Feb 2000 Posts: 4,886 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 4,886 | Think of this way, all the ratio means is the drive shaft turns 6 times before the ring gear (tires) turns once, if its a 6:1 ratio. Is really easy once you know the secrets ! Joe | | | | | Joined: Mar 2006 Posts: 77 Wrench Fetcher | | Wrench Fetcher Joined: Mar 2006 Posts: 77 | Thanks for all the replies!!
Okay... I counted the teeth and there are 10 on the pinion gear and 39 on the ring gear... so that divided would be 3.9, so that means the ratio is 3.9:1? Or am I way off?
The reason I asked at all though was because with this rearend under a 1961 Chevy 1/2-ton with a 235/3-on-the-tree, the truck used to be able to go like 70 miles an hour up hill with ease and then would still be able to "push" the driver to the back of his seat. So I was wondering if these might not be stock gears, or could those trucks just do that? | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | That is pretty much the standard ratio for these trucks from 55 to the late 60's. There was some variations & after 67 there were more available ratios. You are pushing a 235 pretty good at that rate but a good one will do it. Years ago Back when I worked for a truck line we had a 58 for a service truck. I drove it 200 miles on the Kansas Turnpike without hardly ever letting up on the gas. It would go 75 up hill & 80 downhill. It still ran good a long time after that.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Mar 2006 Posts: 77 Wrench Fetcher | | Wrench Fetcher Joined: Mar 2006 Posts: 77 | Thanks for the info! Yeah, that 3.90:1 is exactly what the book says for what the truck has.
The 235 is a very good motor. It's the only thing that isn't/wasn't stock to the truck. The numbers say it came out of a car. Whenever my great-uncle used to drive the truck he would say, "Are you sure there ain't a V8 under there?"
Even now - 20 years later - that same 235 runs GREAT. Except for a darn small crack in the block!!
Again, thanks for all of the information. | | |
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