Hey all,

Just wondering a few things about differential "sizes" as I just noticed that the seal where the driveshaft hits the diff looks kinda crushed and worn (not leaking that I can see though!) and I want to make sure my differential has enough fluid in it, as it has 186K miles on it. I may be interested in getting a chrome cover for it (bling bling!), and making sure the main gasket is in tact, in which case I'll fully drain the diff and top back up with oil.

I just noticed the transmission is leaking gear oil, and that explains the burnt oil smell after longer drives, so I'll be topping it up now and again until I get the chance to take it out and replace all the seals. There will probably be a thread on that later

Anywho, I've noticed lots of talk about 8.8 and 9.0 rear carrier sizes, as well as all the dana rears. I have a 1986 F150 Stepside with the 4.9, which obviously limits the choices of rears that were available. Axel code is 18, so according to Gary's site thats a ford rear with the 3.00 rear gearing. I assume thats a 8.8 carrier?

Long story short, am I right to assume its a ford 8.8, and what is the main difference in rear carrier size across the years and manufacturer?

Thanks for all the help guys. I wanna make sure whatever parts I get are correct, never hurts to know what ya have!

 

If there is a cover on the rear of the diff that unbolts then you have an 8.8. And that # is actually the ring gear diameter. While the diameter of the ring gear doesn't really mean much, the larger the diameter the heavier the differential in most cases.

 

The 9 inch Ford rearend has a "legendary" reputation but the 8.8 has a very good reputation also. Most of Ford's re-designs in these years was for fuel efficiency. While the 9 inch is very strong, the 8.8 design robs less power and is lighter.

 

Yeah I do see you can rebuild most rears regardless of size with most ratios by swapping the ring/pinion, much more reasonable priced for the common sizes here than say swapping the ring&pinion on my spitfire for the eurospec 3.63 from a 3.89. (About 120-150$ worth of parts for the ford instead of 300-500$ for my spit)

I guess that clears things up, and I do intend on sticking with my 8.8 instead of "Upgrading" to a 9", as some people say its not really that big of a difference, and some actually prefer the 8.8 from what I've read.

I guess my biggest question was how do you tell what you have? I haven't hunted for it, but there are tons of tables that will tell you what gearing you have, or what was offered those years, but none actually tell you the size. Is it just a year/manufacturor thing? Like did ford go to a 9" in '88 and never look back, or were the two offered alongside one another?

 

I think the 8.8 and 9er were offered side by side for a year or so. Not sure.

ID chart. Note the 9 has a drop-out carrier, the 8.8 is integral with a rear cover. As another member (69cj) noted about a certain engine ID, ..."Helen Keller could spot it..."

http://www.differentials.com/wp-cont...8182057479.png

 

1986 was the last year of the 9" for good, and having a 3.00 gear ratio means you have a 9". Generally, having a 2.47, 2.75, 3.00, 3.25, or 3.5 ratio guarantees you have a 9", while 8.8s are 2.73, 3.08, 3.31, 3.55, 3.73

 

AH after reviewing some images I see the difference is pretty cut and dry. I'm not 100% on if my truck is stock in terms of the drive train. I know the motor is correct/never been changed, and my truck hasn't been messed with TOO much, but my transmission looks like its not bolting up to the backing plate propery as there are extra indents and such that aren't bolted in place (Multi fit bell housing?) so it could have been swapped, as transmission code C is supposed to be a 3speed (not sure if that C code means its a 3 speed with overdrive, because the way I read it off the table on Gary's garagemahal was that it only has 3 foreward gears no "overdrive" - a 3 speed with overdrive makes it a 4 speed in my book, but regardless my trans does have 4 foreward gears)

So the point of that thinking aloud up there ^^ is that my rear could be not original. but I'm pretty sure its an 8.8 with the bolt on back cover and not the drop out carrier. Which means its probably not a 3.00 gearing if thats the case, unless I have an extremely unusual gearing for my differential. I'll have to spin the drive shaft the next time the rear is off the ground to get a better idea. I'll crawl under there and look after work today. Not much time for trucks and triumphs during the week I'm afraid