Hey I've an 86 Thunderbird TC and the 7.5 diff in it went out. I'm looking to swap an 8.8 in it and have a question about it. I've found an 8.8 out of a 1986 302 automatic mustang. Will that one bolt right in? And what will the gear ratio for that be? Will it easily work in my car? Thanks for any info
There's some good write ups on here of you look around. If i was to source a used tear ems fir mine I'd look at sn95 mustang. The length is the same. And get 5 lugs
I don't want five lug right now, I have nice wheels and tires for 4 lug.I just want to know if that'll bolt in.
It will bolt in but it will be narrower than what you have. The Thunderbird has longer axles. Yes, it will bolt in.
The 86-93 Mustang 8.8 is a direct swap, but shorter in width, so the wheels will be tucked in.
The only correct width drum brake 8.8 is the one from an 88 Cougar XR7. I have one under my Thunderbird.
Alright so wheel spacers will be totally easy to bring them back out, sweet. Thanks so much. Just so I know, what are some other 8.8's for other vehicles that'll work with some easy modification?
I have another question. There is an 8.8 with 4.10 gears out of a 1989 F150 that is closer to me. Would that bolt in easily? Is there a way to convert the 5 lug to 4 lug? And like with sizing and all, would it work?
the 87-93 Fox Mustang 8.8 is approximately 0.75" narrower per side than a 94-98 SN95 8.8 rear end. The SN95 is the closest to the Turbo Coupe 8.8 in width hence the reason all that desire to move to five lug get the SN95 rear end. With that being said and the fact that you want to remain 4 lug the 8.8 out of the Fox Mustang you have located will be right at 0.75" per side narrower than the rear end you currently have. Spacers of this thickness will need to be like the following however these are for five lug but you get the idea:
https://www.youtube.com/watch?v=avTdeSMMXyk
The reason for these is that you do not have enough wheel stud length on the 8.8 to accommodate 0.75" of slip on spacer. You are better off looking for a 87-88 Turbo Coupe rear end (getting harder and harder to find), rebuild what you have, or buy the Fox Mustang 8.8 and buy two wheels that match what you have and get them with the right offset and back spacing to move the wheel out 0.75".
Gears in the Fox Mustang 8.8 out of an auto were typically 3.08 and a few had 3.27.
No an F150 rear end will not fit our cars without some serious mods. and by serious mods I mean cutting the rear end housing up as the center sections is offset to one side. I have to say this but the four lug rear ends are starting to become harder and harder to find so the sway to five lug will eventually be the only way to go if you want an 8.8 rear.
Alright thanks so much, I think I'll just go with the 86 4 lug 8.8 and find some wheel spacers that'll work. Thanks so much though
If it is stock and never been touched you should consider a trac-lok rebuild kit and at a minimum new axle bearing and seals for it as these parts do not last forever.
https://lmr.com/item/LRS-4700A/Mustang-Ford-Racing-88-rear-end-Traction-Lok-Clutch-Kit
https://lmr.com/item/M1225B/mustang-rear-axle-bearing-seal-kit-ford-racing-m-1225-b
Yeah I think I actually will do that. Thanks so much, I don't know too much about this rear end stuff. After replacing those, this diff should be pretty tough? And I have no idea how to do that clutch rebuild stuff, but I'm sure I can find a video.
The f-150's and mustangs with 400+ hp are still using basically the same rear end from the factory.
Rebuild trac-lok:
https://www.americanmuscle.com/ford-88-traclok-kit-cust-install.html
Replace axle bearings and seals:
https://www.americanmuscle.com/frpp-rear-bearing-kit-8604-cust-install.html
Having a slide hammer to remove the bearings is the only way to go. You can usually rent one at the local auto parts store. You will also need a bearing/race installation tool that you can also rent at the local parts store. Don't forget to add the clutch friction modifier and use a quality rear gear oil.
Only other think I can tell you is make sure the pinion seal is not leaking. You can find a plethora of videos on how to do this on YouTube. Biggest thing to remember is that this rear end most likely has a crush ring to set the pinion gear preload so you will need to pay attention on how to mark the pinion nut to index it to the pinion shaft and the pinion to index it to the rear end. This will allow you to put the preload back to where it was without using a new crush ring and having to pattern the gears. However, if someone has been into it and changed the gears then they may have installed a newer type of preload that has a solid sleeve with shims to set the preload. I have this on both of my 8.8's and it makes changing out the pinion seal a breeze. Just put the sleeve on, shims, and retorque.
Swap your axles over to the 8.8 and you won't need the spacers. I just put a mustang 8.8 in my 1984 TBird and swapped the axles out and kept the proper wheel spacing
Not necessarily the case with his '86 7.5. This was around the time when the 7.5 axle HOUSING got wider. Your '84 has the same housing width as a Fox Mustang, and the 87-88TC 8.8 (and 94-98 Mustang 7.5 and 8.8), and so the axles are an easy swap, as long as the brakes are swapped as well.
86-88 7.5 housings are wider.
OP, measure -to- (between the brake backing plates) and compare between the housings.
See the spreadsheet posted HERE (http://www.foxtbirdcougarforums.com/showthread.php?13253-Deciphering-Fox-Axels&p=138359#post138359) for reference.