Can I swap a 9" into my 1987? Its an F150 (see sig) that I have been building for awhile now, and the rear 8.8 just went out. I would like to put a 9 inch in it, as they're tough as hell, but I need to know two things.

One, do/did they ever come with a 3.55 gear ratio? I looked on Randys Ring and Pinion and they sold a set of 3.50s but not the 3.55s that I have now.....If I found one with a 3.50 ratio, could I run that with my 3.55 front end and not have problems since they're that close?

Two, I've heard about not being able to ditch the 8.8 because of the speed sensor on top of the housing, but knowing the off road world, and how popular the 9 inch is, someone has had to have found something to fix that. I dont have CC, but this is a daily driver.

Thanks all

 

Your 87 has the VSS in the rear end? I thought this started later 92?. My 89 Bronco did not have a VSS in the rear end and if your truck does I think you are stuck with the 8.8. You might have an ABS sensor in the rear, but I am pretty sure if you have a cable driven speedo you have a cable driven VSS. Disconnecting the ABS sensor will make the light come on but the ABS on my bronco never worked right and actually stopped better because it did weird stuff when ever the ABS tried to engage. Heck since your tuck is a 5spd you might not even need the VSS I really don't know on that one. As for the gearing the I have only seen 9s in 3:50 never 3:55 doesn't mean they aren't out there but if they are they are not near as common as the 3:50s.
-Johnboy

 

I don't know what it is, I didnt think it was a VSS either because of the age, like you said, I thought this was 1992 technology, but there was an electrical plug there and thats all I could think of. If its the ABS sensor that makes sense, as the light has come on at random times (now that I had the rear end apart I see why). My ABS has never worked since I got this truck, so if I just took that plug out, capped the end of the electrical line and tucked it out of the way it should be fine right? Can I short it so the light doesnt come on, or how does that one work anyway? I would like to keep the light, as it does work for other things, but if not, its not a big deal for me..

And yes....I had a cable driven speedo, but its been long replaced with an electric one from AutoMeter (much easier for gear swaps and tire changes)

Thanks johnboy, hopefully we'll get someone else in here to answer both of our questions.

 

Just FYI a 9" housing out of a 80 and up F-150 is a bolt in deal, the 79-78 might be never could find out for sure on them or the drive shaft length. I looked into this swap when I broke my 8.8 in my Bronco but sold the truck before I got it done. Heck I did the ZF swap too.
-Johnboy