The Stovebolt Site Forums The Shop Area Driveline ring and pinion

I have a 48 chev 1 ton panel and think the rear end has been changed. My chev. manual said that the # stamped on the right side of the rear end tells me it is a 1/2 ton rear end. If the # was on top then it would be a 3/4 or 1 ton. The number is 8698535. The location then tells me it is a 4:11 and not the 4:57 of the 1 ton.

What I want to do is change the ring and pinion. Jim Carter said that they can take the 4:11 to 3:55 but will not work if it is the 4:57. I want to go to more shows this year but it would help to bring down the rpms on the longer drives. Right now 50 mph is about what works and it would be nice to get 60-65.

Thank you for any help.

easiest way to find the ratio is pop the cover and count the teeth .... also, 6 lug = 1/2T, 8 lug = 1T

Bill

Bill it is 8 lug and can you jack the back up and mark the drive shaft then turn the wheel. I did this and turned the wheel 4 turns plus a bit. I think that would make it the 4:11. (I think)

It's very difficult to tell the difference between a 4.11 and a 4.56 unless you do a few things to get a more accurate count of driveshaft turns. Here's how I'd go about it:

Jack up one rear wheel, and turn the wheel, not the driveshaft. The differential gears will double the wheel speed, so one turn of the rear wheel will result in approximately 8 1/4 turns of the driveshaft for the 4.11, or slightly over 9 turns for the 4.57 gear. A 5.14 ratio (which is probably what a 1 ton will have) will result in slightly over 10 turns of the driveshaft to one turn of a single rear wheel.

Look here for the code and I'll check the number out for
you and let you know just what you have:
http://www.pbase.com/dennygraham/image/114181134
The seven digit number you posted is just the casting number,
that's the same on all that series casting.

Denny G

Recheck your 8698535 casting #.
It should start with a 3.

Could be 3699535,
Used from 1946 thru 60
on 3/4 & 1 ton.

The stamped number Denny posted is what you need.

Codes for a 1949 Rear axle
http://chevy.oldcarmanualproject.com/chevyresto/4858.htm

hotrod;
I jacked up the one side and turned the wheel one turn. In doing that the driveshaft turned only 2 1/4 turns.
What do you think
thanks

OK- - - -I miscalculated the ratio change. The ratio should be around 4.50:1 (probably the 4.56 gearset). Try turning the driveshaft 4 1/2 turns with one wheel jacked up. You should get 2 turns of the rear wheel, since the spider gears are doubling the wheel speed. That's one reason not to get heavy on the throttle if you ever get one wheel spinning in snow or mud- - - -the wheel that's spinning is doing twice the speed the speedometer is indicating.
Jerry

Jerry,
Just so I know--does that mean if you jack up both wheels and turn the driveshaft then the wheel should go around 4 turns + a little (4:11) like it would if you where going down the road.
I will give it a try but also trying to take the back cover off to see if I can see the stamped #s on the ring gear.
Rodger

Her are a few of the GM gear ratios:

43/14=3.07
36/12=3.08
3.23
43/13=3.31
37/11=3.36
3.42
39/11=3.55
36/10=3.70
41/11=3.73
39/10=3.90
41/10=4.10
37/9=4.11
50/11=4.55
41/9=4.56
32/7=4.57
39/8=4.88
36/7=5.14

The ring gear tooth count & pinion gear tooth count, is stamped on the outside edge of the ring gear. Divide the big number, by the small number & viola, the gear ratio. I keep this information on my notepad on my phone, as a quick reference guide.