Axle ratios

Reply Subscribe

Thread Tools

Search this Thread

Mar 3, 2002 | 10:57 PM

69 F100 4x4

Thread Starter

Senior User

Joined: Dec 2001

Posts: 109

Likes: 0

Axle ratios

How can I find out what gear ratio i have in my axles, Ive got a 9" rear and a Dana 44 front. Also is it possible for the front axle to have a different ratio or are the people who claim they have different ratios full of crap? thanks

Mar 4, 2002 | 09:13 AM

highcountry

Junior User

Joined: Mar 2002

Posts: 93

Likes: 1

From: Montrose USA

Axle ratios

There are three ways I know of telling the axle ratios. First look for an axle ID tag under one of the cover bolts (or 3rd member bolts0. In the event that they are missing (likley) you can lift the wheels off the ground and mark the driveshaft with the trans in neutral and turn the tire once around. Make sure someone turns the opposite tire in the same direction so it is the diveshaft that turns. Then count the number of times that the driveshaft turns in relation to the one turn of the tire. Say the driveshaft turns 3.5 time for one turn of the wheel you ratio is 3.5:1. It helps to know what axle ratios are available for a given axle because you will need to guestimate. The third and most difficult way is to access the ring and pinion by removing the cover or taking the third member out of the housing (depending on which axle). Then count the number of teeth on the ring gear and divide it by the number of teeth on pinion. That will give you your ratio. The middle method has always worked well for me. Easy and effective.

Mar 4, 2002 | 03:59 PM

Chuck P.

Elder User

Joined: Jun 1999

Posts: 861

Likes: 0

From: SE PA

Axle ratios

Just to add a little, common ratio's are 3.50, 3.73, 4.10 and 4.56. Not saying in your year there couldn't be a ratio or two in between though! As for the different ratio f/r, yeah, that's common practice. They MUST be close, for example, had 3.54 in the front and 3.50 in the rear, swapped to 4.09 front and 4.11 rear. Unless your running a different diameter tire front and rear, the ratios should be close or things tend to break, don't try a 4.09 front and 3.89 rear, that's just to much binding on the drivetrain. The reason for this is two fold, first, a little tension in the driveline is a good thing, takes up the slop. The second, is sometimes they just can't make the exact ratio for the front and rear due to pinion and ring size differences, this has to do with strength and set-up (case size limitations) as well as overall ring diameter.

Mar 4, 2002 | 06:07 PM

redranger1

Posting Guru

Joined: Dec 2001

Posts: 1,110

Likes: 0

From: Iberia, USA

Axle ratios

my uncle ran 4.88 in the rear ans 4.56 in the fron of his pulling truck fer a couple seasons. but he did that himself. i dont think that the truck manufacturers would split the gears from the factory.

-nathan

Mar 4, 2002 | 08:04 PM

69 F100 4x4

Thread Starter

Senior User

Joined: Dec 2001

Posts: 109

Likes: 0

Axle ratios

Thank you all for the replys the helped me out so much. I really appreciate it. Thanks

Mar 4, 2002 | 11:29 PM

kspilkinton

Postmaster

Joined: Jul 2001

Posts: 4,038

Likes: 3

From: South Kitsap County, WA

Axle ratios

The axle ratios must be within 1% of each other to avoid vibration in the drive train and a messed up transfer case. In my case the 3.50 rear is a little under 1% from the 3.54 in the front. It came from the factory this way so it was Ford's design and not my own. The next year when Ford swapped over to the 8.8" rear they changed the rear end gear to 3.55 but kept the 3.54 Dana 44. It's a closer ratio and has less wear on the drive train.

Some places claim to have matching ring and pinion ratio sets for both front and rear.

-Kerry

Mar 5, 2002 | 07:21 PM

kspilkinton

Postmaster

Joined: Jul 2001

Posts: 4,038

Likes: 3

From: South Kitsap County, WA

Axle ratios

Wouldn't let me edit my post from last night....
Anyway I was going to add that the reason why Ford puts stickers on their 4x4's that say you should not shift into four wheel drive on dry surfaces is because of the slippage needed due to the slightly different gear ratios in front to back to prevent damaging the transfer case. The AWD vehicles don't need this warning because of the viscous clutch packs they use in their tranfer cases which help to distribute loading and disapate binding...and also because you can't shift them out anyway