well i bought a 9 inch out of a 68 f100 when i measured it up it has 4 inches of offset from centre is this normal if so do i have to offset my engine 4 inches to compensate when i read the article on this site it states the 73 torino right side axle can be swapped for BOTH axles if thiss is true then both axles would have to be the same length but my rear diff has two different length axles I also read that car axles were equal so that the driveshaft runs in the tunnel
Do i have the right diff info would be great

 

It doesn't matter that the differential is not centered in the rear end and you do not have to offset your engine. The driveshaft will work fine with the angle. You do however need to make sure you have the pinion angle set up to be in phase with the engine/tranny angle. Whatever angle down your transmission is set at (usually 2-4 degrees) the differential pinion needs to be set to be upward at the same or nearly the same degree to keep the centerlines parallel. Hope that makes sense. Do a search on pinion angle if it doesn't as this has been discussed several times.

 

well I appreciate your response thanx eh the article stated that the rear diff has two equal length axles not true thus the confusion I understood that a pinion angle at 2-3 degrees down had to be set I just didnt know how much side to side was allowed I was told that the driveshaft had to be as close to inline as possible by the driveline shop here thanx again

 

http://www.clubfte.com/users/jniolon...nephasing.html Here's an excellent explanation of driveline phasing done by John. I haven't tore into my '68 9" yet, but 74-86 truck rear ends have equal length axleshafts....Broncos do not (66-77). The idea is that with equal length axle shafts and bearings, the payload distribution in the bed will bear the same weight on both sides. The pinion is offset to mesh with the ring gear which is offset to allow the carrier to to be equal distant between the two sides of spider gears. Here's a picture of what your carrier should look like. Also, if you find a tag on there, post the codes, and someone should figure it out.

 

https://www.ford-trucks.com/user_gal...197520&width=2 Here's the '68 9" in my gallery

 

sure looks like my diff 325 and all mine was out of 68 f100 engine was originally offset the same as the diff i wonder if i can leave mine centered others say yes now the article shows parallel engine and pinion however the intake is actually tilted for level carb and oil pickup so the article is flawed and that is why i question its relevance thanx havi for your help im a refrigeration and ac technician if i can be of assistance feel ree to ask

 

Also, here is a link to an outstanding site on the 9" in general:

Kevinstang's Ford Nine Inch Differential Page +

Julie

 

The article reads correct to me. As shown the engine and/or diff can be offset when looking down from above. I'm sure there is an acceptable limit but I don't know what it is. The important part is that the engine be mounted straight so it's centerline is parallel to the pinion centerline. Once that is accomplished then look at parallel centerlines from the side view. If you want the carb level then you will have to mount the engine such that the carb is level when bolted down. Then measure the angle that the tailshaft points down. Now you will have to shim the rear axle to rotate the pinion to the same angle as the tailshaft only pointing up. Then when you imagine those 2 centerlines they will be parallel. If you're using efi and not worried about a carb being level you can match the tailshaft angle to the existing pinion angle.

 

One direction or the other or both needs to be offset for the driveshaft U joints to work properly. A perfectly straight driveshaft thru the centerline of the engine and rear axle pinion will tear up the U joints in short order.

 

Ax is right, there wouldn't be any "swirling motion" for the u-joint caps to stay lubed.

the rear has to move up and down as the suspension travels, so the happy medium is to have the pinion's up/down angle equal to that of the transmission output shaft. If the truck sits lower in the front (the way I like it, lol) then the engine leans back to keep the carb level. That means a downward-to-the-rear angle. The rear end is thus tilted up...as it's the rear most end-point. But the output shaft does not point straight at the rear diff. Say for example it's 3 degrees. The rear does not point straight up to the output shaft, instead it pointsup at 3 degrees as the example ensues (for a lack of a better word)

Side to side offset of the engine is typical on all Fords. However, not all rear ends will be side-side offset, where the driveshaft travels up through the tunnel in the center of the car, the rear pinion will be centered, IE unequal length axle shafts. (Fox-body 8.8's are an exception, the shafts are equal lengths, but the 8.8 may have a different location for the pinion, since Ranger 8.8's use unequal length axle shafts....so it seems 8.8's are opposite of the 9") The trucks don't have a tunnel to worry about. As I said earlier, the shafts are equal length to support a load evenly. So then the pinion is offset as well. 4" seems a bit much, and may warrant a look-see. Most engines are offset less than 2", and the rear shouldn't be any more than that.

Notice the length differences in all these different makes and models: Axle Shafts for Light Duty Pickup Trucks and Cars rear differentials

 

In measuring the overall length of the 2 Ford 9" housings that I got last night the actual pinion/yoke is exactly centered in relationship to the overall length of the housing. So putting the differential in the chassis and placing it where there is equal width between the outer frame rail and the tire/brake backing plate on both sides places the pinion directly center in relationship to the trans output shaft and the driveline itself. The pinions are natural offset to one side to compensate for the ring gear/spool assembly so one side of the differential housing is shorter on one side.

 

well if you look at the thread i started in 67-72 ford truck you can see the offset thanx for all the interest i am learning lots

 

 

 

yeah, I just posted over there. you should have 40" between spring pad centers.