What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Axle Ratio Question

O

Old_Miner

Registered Member
Joined
Feb 13, 2006
Posts
9
Reaction score
0
Location
Idaho
I have read in the forum in the past that if you rotate the tire one full revolution and count the times the driveshaft turns that is your axle ratio.

I have an 1987 GMC Full Sized Jimmy (K5). I turn the tire one turn and the axle only turns 1.75 times. Surely that don't mean I have a 1.75:1 axle ration.

There are no RP codes in the glove box and I wanted to find out the axle ratio so I can gear it for 35" tires.

Any help will be appreciated.

Thanks, Tom
 
You sure you didn't move it just a 1/2 turn (180 degrees). If you did, then you'de have ~3.5:1 gear ratio (brain fart on the exact number there)
 
Could try doing it the opposite way. Rotate the driveshaft until the tires turn one revolution.

:dunno:
 
If you are only turning 1 tire you need to multiply the Dshaft rotation by 2. With an open dif if only 1 tire spins it has to spin twice as fast. Have I confused you?


Lets say you have 4.10s The driveshaft spins 4.1 times for each axle revolution. If you hold 1 tire so it cannot spin the spider gears will spin in such a manner that if the driveshaft spins 4.1 times the wheel that is spinning will spin 2 times.

The ratio should be 3.08 or 3.73 if they are factory. I do not know if they offered 3.73 in 87 or not mine was 3.08.

Ira
 
Yes, Totally confused

Yes, It kind of makes sense.

I spun the tire with both rear wheels off the ground and I noticed the other one turned the opposite direction, so I put that wheel on the ground so it could not spin.

I spun one wheel and the drive shaft rotated 1.75 turns. So if I multiply that times two, I would guess that I have a 3.42.


GM10-308 1258709
3.08​
40-13​
$207.33​
GM10-342 1258710
3.42​
42-13​
$207.33​
GM10-373 1259441
3.73​
41-11​
$207.33​


Does this sound right? Also, who would you recommend me order gears from?

I am thinking about going to 4:11 to turn 35" tires. Does that sound right?
 
yeah, i know, i'm headed that route myself... shoulda put "minimum" after that..

for the average every day DD joe asking, i figure 4.56 will keep the revs and fuel ecomomy reasonable and he'll still use OD.. plus i'm assuming he's talking about a 10b regear...

i'm gonna run 36's with the 700 so i'm figuring 5:13's for myself, but i'm waiting on getting 1 tons..
 
Yeah, I wish I could afford 1 tons, but I have the standard 10 bolt. If I do the gear change myself, I figure it will cost me around $500.

If I get a shop to do it, they quoted me $1500.

If I get 1 ton axles it would cost $3500.

It sucks to be on a budget.
 
Old_Miner said:
Yeah, I wish I could afford 1 tons, but I have the standard 10 bolt. If I do the gear change myself, I figure it will cost me around $500.

If I get a shop to do it, they quoted me $1500.

If I get 1 ton axles it would cost $3500.

It sucks to be on a budget.
Click to expand...

If you do it yourself it would cost about $200 for gears and $100 for install kit it that per axle. The shop that told you $1500 could lick my nuts. Shop around. I have heard of guys getting it done for about $400 per at a shop. I did my 14FF and knowing what I know now I think I would have the patients to do my 60Front.:D There is nothing "hard" about it just takes a little time.

Ira
 
Only thing I have heard is that aligning and setting backlash can be hard. I guess I will find out.
 
Nice part about axles like a Ford 9" or 14bFF is you don't need to press-on/off the pinion bearing each time to change the shims, and carrier bearing use screw adjusters.

Good axles to learn on. All the more reason to get the 14bff now rather than later. :D

As for budget... last time I did rear brakes, I changed a whole axle instead... it was cheaper. :haha:
 
It is not hard it is quite easy it just takes some patience and a little time to mess around with changing out shims and what not. Some guys get frustrated cause when you change pinion depth it effects backlash so you have to keep removing and installing shims. For those axles make sure you remove the bearings in 1 piece, then clearance the inside race so they slide on and off by hand. Now you have set of setup bearings. It allows you to change shims easier on the carrier and the pinion. The first step is to get your pinion depth set properly, then adjust your backlash.


Ira
 
Thanks for the good advice. Most excellent.

I have been looking for a good how to article on change the ring and pinion, but have not found one yet.
 
You must log in or register to reply here.

Latest Posts

Top Bottom