Drivetrain 1985 Convertable - 373 gearing conversion

[1TDUBB1]

From what I've been able to figure out is that this car has a 7.5" rear end and by looking at it's shape being more round than oval, I believe confirms that. A friend of mine has the 373 gears but they are on an 8.8" Detroit Locker. He thinks that the gears will still fit in a 7.5" rear end. Does anyone have any insite on this situation.

Or if they wont fit, does anyone have the 7.5" gears and want to trade for the 8.8"?

 

[General karthief]

Only thing I know about the 7.5 is it uses a 10 bolt ring gear.

 

[1TDUBB1]

I've been researching this weekend and haven't found and answer to whether or not these gears will fit, but that's interesting, this one has 10 bolts.

What I have found out though is most people swap the whole rear end for the 8.8" to handle all the HP there adding. But I'm not trying to go crazy with this car, but as is, the power is pretty disappointing for "5.0". It sounds to me like the 373 gearing's going to help a lot, but I think I can get this from the stock 185Hp to something over 300hp, with some fairly simple bolt on's. Now I know I'm not the first one to say this, but I think thats all I really need, lol........

So, the 7.5" shouldn't have any problem handling the 300-350Hp. But the 2 of the 3 reasons that everyone goes up to the 8.8" are options I think I'd like to have.
1. The 5 lug wheel upgrade would be nice, then after talking to my buddy that just got new rims for his 2017 said I could have his stock wheels. I'm just a little worried that the 17" rim will be to tight up front.
2. Converting to disk breaks is a huge plus.....or is it? 70% of breaking is up front anyways. I'd like to hear opinions on this one.

Good news is, I dropped it off at a shop and had a complete diagnostics done and the only issues were a small coolant leak from the heater core line.(it's at the T were the last guy bypassed the heater core). And they couldn't nail down my idle issue, but suggested replacing the fuel filter, flushing the line, and cleaning the 2 injectors. Oh and the A/C chock does not engage, but I'm pretty sure that's because it was also disconnected for the last 6 years, I bet thats an easy fix.

 

[2000xp8]

Couple things.
Nobody sensible invests any time or money in a 7.5.
You don't simply swap the gears, you have to check the back lash, shim as necessary and while you are in there, if it was never rebuilt, the traction lock should be replaced or rebuilt and you should get new bearings.

The right offset 17's fit fine (I have no idea if the wheels off a new car fit right).
Read through the 5 lug brake swap post (I think it's in the stickies).

Bigger brakes and discs in the back are always worth it. Not only do they stop better, but they look better and are 1000% more reliable.
But parts are going to add up and if you have to pay labor, that will probably be quite a bit.

 

[Mustang5L5]

You can put disk brakes on a 7.5" if you'd like. They will bolt on, although I don't know if I've ever seen anyone upgrade a drum brake equipped 7.5" to rear disk. I'm sure it's happened, but you can get an 8.8 pretty cheap, go through it all on a benchtop and then swap the axle as a unit.

You cannot install 8.8 gears in a 7.5" axle.

 

[1TDUBB1]

Thanks mike, you've confirmed the two main things that I've been figuring out. And 8.8 gears in a 7.5 was a pretty obvious no, but I've seen stranger things. And that's my plan, get an 8.8 from a salvage yard, since I have all brand new guts, and take my time with it on a bench.

Any advice on what year make and models fords will have an 8.8 rear that's the same width? Chopping something down to size and re welding it just sounds like a terrible idea. I'm in no hurry and wanna get it done right.

The right offset 17's fit fine (I have no idea if the wheels off a new car fit right)

From what I've found, it sounds like it'll have to be a pretty low profile tire, but they should fit. But you've made me wonder, if there's a slightly narrower rear end out there, would that help with tire fitment?

 

[Mustang5L5]

Easiest, most direct bolt on with 5-lug disk brakes would be a 1994-1998 8.8 out of the GT or Cobra.

Any 86-93 mustang 8.8 will work as a direct bolt in too.

 

[2000xp8]

I think you will find that working on a rear when it's installed is easier than it is out.
You have to pull races with a slide stick, they have to be hammer back in, (with the proper adapters or whatever you call them), then everything needs to be torqued. The emergency brake also comes in handy to hold parts in place.
None of these tasks are easy when the rear wants to move.
Some shops charge more to do a rear out of the car than in, based on these reasons.

 

[1TDUBB1]

I can see that, 2000xp8. So get the shell and everything cleaned up and repainted on the bench, but add the axles and gears after it's installed.

Thanks guys, looks like I'll be doing the Central Texas junkyard crawl this weekend.