curtis73

1) On older fords, they listed the rear axle ratio directly on the door sticker. On my 98, it just says axle "19". Does that refer to the ratio? If so, what does it mean? I'm trying to find out the ratio.

2) I found a 2001 F150 axle with discs. Bolt-in swap? Probably a different MC or prop valve?

driver444

That "19" you saw is the axle code. The # itself doesn't mean anything unless you know what a code 19 axle is. For example, my 1996 F350 has a "C5" axle, meaning its a 10.25 inch 4.10 ratio limited slip axle, (at least before I put the locker in it)!

Your gear ratio is stamped on a little metal tag attached to your rear differential cover by on of the cover bolts, usually on the passenger side.

For example, 3 73 = 3.73 ratio regular axle
3 L 73 = 3.73 ratio limited slip axle

There is a chance that if you look up "rear axle" in the manual it will tell you what code means what. My 1996 was that way.

As far as the type of axle, if it has 10 cover bolts, it's a 8.8" Ford axle, and if it has 12 bolts, it could be a 9.75" (most likely), or a 10.25" Ford axle.

As far as the swap, I believe all F150s that body style, (1997-2003) had the same leaf spring spacing, and shock placement. I believe that axle will infact bolt in, but yes, you will have brake issues to deal with. Might be easier to find one from the right year truck. BTW, Your "98 doesn't have discs?? I thought they did. Learn something new everyday I guess

willys5555

what swap are you trying to do? are you upgrading or just replacing because something is broken? but yes just look at the metal tag like noted above ^^

i also would suggest getting the same year axle for your truck...that would eliminate the possibility of master cylinders and stuff of that sort. unless you can get that axle at a great price then you could justify spending the money on a master cylinder and ect. you know what i mean...weigh the options and the money and do whats best.

im currently looking to swap the bigger 9.75 in place of my 8.8. the only thing i have to change would be the driveshaft has to be shortened. (also on a side note...does anyone know FOR SURE if the 9.75 has same lug pattern as 8.8s? i have heard both ways...)

good luck.

driver444

On that side note, YES, the bolt patterns are the same.

willys5555

Driver444 thank you very much...it seems i have gotten different answers. but im hoping your right cause that will make my life so much easier maybe the 9.75 changed on newer models...is that how some could be confused? either way, my truck is a 97 and i found a 9.75 out of a 97 so i should have no problems. Thanks

and curtis, good luck with what ever your doing...im not quite sure yet. lol

curtis73

I'm not too worried about master cylinder/prop valve issues. Its just a matter of looking up which parts were different. In my brake swap experience with GMs the only difference is prop valving. In fact, in many GMs where rear discs were an option, absolutely nothing changed. I re-valved my 96 Impala SS because the MC and prop valve was exactly the same as disc/drum cars of the era.

On the earlier end of the 97-03 trucks, the rear discs were just an option. They became standard on XLTs in 99-ish, then standard on all of them in 01 or 02, but that's just from my observation of what F150s had them and which ones didn't.

curtis73

There is a guy locally who has a cheap 9.75" (which is what mine supposedly is) from a later F150 with the discs already on it. His axle is 3.55:1, and since mine is 4x4 (and I'm happy with the current gearing) I need to know if mine is 3.55 as well.

I want to swap to discs because... well, they're discs. The drums are more than satisfactory, but discs are a bit nicer to maintain and have other benefits as well; less likely to grab, fewer parts for engineering simplicity, yadda yadda. His also has the limited slip and mine doesn't, so that would be another big reason. Two birds with one stone.

So, the money math needs to be done on my part... cheap axle isn't so cheap if I have to swap gears, so finding out my current ratio will help me decide that. As far as compatibility is concerned, no worries. The only things that really could be different are MC and prop valve, both of which are cheap. (and probably brake hoses, but his already has recent/good hoses attached to it.)

Paints-n-cows

Your axle is an open 3.55. My '98 has the same code.

I have been searching for where I found that information but I can't seem to find it. If I do, I will post the link to it.

curtis73

I also learned (frustratingly) that mine is an 8.8. The tags on the cover don't really tell me anything. The 10 bolts tell me its an 8.8. The tags say things like 8E60 and then a string of numbers that are all higher numbers that don't seem to indicate anything clear. I didn't write them down, but they say something like 6 8 8 7 4 E. The other tag just says "use synthetic 80w140 only"

3.55 is OK with me. OD makes it lug a little until 70 mph and higher, but I can live with that. I'll just drive faster