Buying an ebay posi unit

gonzalo medina · Post by **gonzalo medina** » Wed Oct 12, 2005 4:15 pm

Help I know my truck has a 9'' rear but don't know whether it is 31 or 28 spline how could I tell it's a 72 with a 390. Seen this great deal on a assembled unit ready to throw in just need some info

roachrider · Post by **roachrider** » Wed Oct 12, 2005 4:22 pm

I believe all the 67-72 truck 9" rears are 28 spline. However, wait to decide on your purchase until someone else that has direct experience with those rear ends confirms it.

gonzalo medina · Post by **gonzalo medina** » Wed Oct 12, 2005 4:30 pm

Thanks I am leaning on a ball park decision I also think it's 28 spline but heard in 1970 they started bring the 31's for those trucks....I guess I have no other choice then to wait till someone approves our hunch

Post by **FORDification** » Wed Oct 12, 2005 6:18 pm

Hmmm....as far as I know all '67-'72 trucks with 9" rearends had 28-spline axles. However, I'm not 100% sure when the 31-spline versions started showing up.

heep70 · Post by **heep70** » Wed Oct 12, 2005 8:12 pm

I agree, 28 spline.

gonzalo medina · Post by **gonzalo medina** » Thu Oct 13, 2005 3:31 am

Alright 28 splines it is and if it doesn't fit my neighbor said he would by it for his ranchero thanks guys

cdeal28078 · Post by **cdeal28078** » Fri Oct 14, 2005 8:02 am

I think the only way to know for sure is to pull an axle.
Some say you can tell by the size of the nuts holding the flange on but I don't think it's 100% either.
Mine has 3/4" nuts with small bearings and 28 splines.
It's a 71
clint

fordman · Post by **fordman** » Sun Oct 16, 2005 12:43 am

the interchange book i was told said 28 spline for 67-72 and 31 spline for 73-79. he was reading the book while i was sitting there.

cdeal28078 · Post by **cdeal28078** » Sun Oct 16, 2005 7:26 am

fordman wrote:the interchange book i was told said 28 spline for 67-72 and 31 spline for 73-79. he was reading the book while i was sitting there.

That's a good guide to go by but these trucks are 25-30 years old. Alot can happen to a truck in that time. Rear ends are changed, engines are swapped out. etc
clint

fordman · Post by **fordman** » Sun Oct 16, 2005 10:22 pm

that true. i was speaking only on what the book said no what some guy may have put in a truck some sort of tractor rear end in a monster truck or some wierd thing

crazyace99million · Post by **crazyace99million** » Mon Oct 17, 2005 10:05 pm

cdeal28078 · Post by **cdeal28078** » Thu Oct 20, 2005 6:22 am

Um OK, just trying to be of help

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