GlassicAnnex

Technical -- Chassis

 

15-55  Rear End

Rear end and gear ratios. -- part of the info below also appears under AOD (overdrive) transmissions.


AOD and rear end gear ratio


Received 3/2008 from Alatorre@charter.net the California owner of car 1148, a 1974 Roadster

It should be noted when changing to an AOD trans the rear gear ratio is crucial. The factors are gear ratio and tire size, as well since most AOD transmissions have a .66 to .70 overdrive.

. A 24 inch tall tire with a 3.00 gear set on the ford 8 inch at 2000 RPM is about 68 miles per hour. To really get the gear ratio right will result in the overdrive coming in at 62 MPH at 1800 to 1900 RPM. There is a formula to get the exact setup.

As to the Ford 8 inch rear the gears available are 3.00 then 3.25 , 3.55 , 3.80 , 4.11 and 4.62 there are a couple of more however not relative here. Overall tire diameter is also a big factor. There is a calculator to help you at http://www.dennysdriveshaft.com/html/potential_speed_calculator.html

 Just fill in your rear end gear the RPM you want to be at and Tire diameter hit calculate.. Then adjust the gear ratio accordingly to find what works best. PS the overdrive value I use is .70 but ask the guy who builds your trans as to the exact gear set he uses. Enter it as a decimal point value.. I hope this helps... My car is still under construction.. thanks

On my rearend (car 1174) and all Ford produced rears was a metal tab.. I decoded my tab as follows.. It is a ford 8 inch for a 74 Maverick 3.00 gear set open end (means non-posi) made in Dearborn during 3rd week of the 3rd month in 73.. I hope it helps a bit

The Annexmaster then checked his 1978 - car 1254 and saw the info below.

This tag was on the passenger side of the car, on the side of the hub facing the front of the car, and it was upside down - I reversed the picture.

WDY               OAAK               7HE                2.79        8                247A

http://www.woodyg.com/fairlane/finfo/fordrears.html

http://www.fordmuscle.com/forums/all-ford-techboard/470670-ford-rearend-axle-tag-codes-posted.html

The numbers on this tag seem to only somewhat relate to anything on the above websites.

The WDY code has an AA (1976-78 Mustang 3.0 gear, 8" ring gear)
and an AK (1977-78 Mustang 2.79 gear, 8" ring gear), but no OAAK -- so I guess that it should be AK, but don't know what the OA would be for.

The 7HE is a Ford internal code which I guess is not important to us..
The 2.79 on the bottom row looks like the gear ratio. THAT seems to make sense.
The 8 is where the Date is supposed to appear.
The 274A is where the plant code is supposed to be.  I found somewhere that A was for Atlanta, but no meaning to the 274 part.

Further discussion of rear ends should address the impact of using a different rear end ratio. What happens to gas mileage and acceleration if we were to change the 2.79 ratio to a 3.0, for example?

***********************

Rich, car 1148, looked up my numbers on the 1978 and came up with the following:

I have examined your tag.. I came up with as follows.. WDY is actually Maverick (Joel the builder HAS mentioned the use of Maverick parts in the past)

 OA is limited slip -- OA is for limited slip not a popular option.. Most were either open diff's or they had an L which was for traction lock..

 7HE threw me but I came up with--  7=1977 H= August E= 5th week -- Now there were 5 weeks in August 77 I had to go look it up.

247A is plant serial number ..

. I hope this helps..

This appears (to the Annexmaster) like reading tea leaves. A quick check of the web did NOT find these codes on sites listing the various Ford numbers. If my car, 1254, HAS limited slip, wow, because I can make it spin the tires by just looking at it wrong! Not all sites seem to list the same codes for the same cars. And the ones I saw did not show the date on the upper row of the tag. Rear end identification does not seem easy to do.

        

 

Replacing the steering rack -

Info from Mark, car 1290, (a 1978-79) received 4/2008.  See many upgrades on his car project.

Well I am in the process of replacing the steering rack. And guess what my Mustang II front end has a Pinto rack on it. Pintos used a 9/16 26 spline input shaft and Mustang used a 3/4 30 spline mine was the 9/16 unit. 

I am replacing it with a FlamingRiver 3/4 30 spline unit all Chrome and I taking off the power steering and going manual.   So if someone is replacing their steering rack they need to check the size spline and number of teeth if they want a direct replacement.