From what I can determine, the 88 Vert had like a 3.9 differential in it (and my seat of the pants feel confirms it), but all the other years had a 4.10, correct?
I may have access to a 90 that's sitting in this guy's yard with a good differential (and rear suspension, etc.) awaiting the crusher.
Is it worth it for me to salvage this stuff and do the swap, and how involved is it?
I looked at the service manual, doesn't look too tough if I just pull the diff. and housing. I'm assuming everything will bolt up.
I know that the gearing in my car doesn't seem to make any sense. First and fifth are too tall!

 

i always thought that all the convertibles had 4.10s in them(including autos) i could be wrong though. Changing the diff isnt that bad. Just remove the axles, and drop the rear subframe a little bit, and unbolt it, and it comes right out
I can do it in probably 1 hour now.

 

All manuals had 4.10's. autos 3.90, excluding GTUs

 

If you look at the specs for an 88 Convertible, I think you'll see that for one year only they had a 3.9 in them. Not sure how much real difference that would make for my gearing, but I'm sure they did it for fuel mileage.
They probably figured out that it didn't help fuel mileage that much and changed it to 4.10 like everything else.

 

I'm not convinced, show me plz

 

The 88 vert (only available with a manual tranny) came with a 3.9 rear end, while all other convertibles (regardless of auto or manual tranny) came with a 4.1 rear end.

Any year non turbo rear end would be a simple swap and done typically is less than 2 hours by most shade tree mechanics, however if you have done it a couple of times, less than an hour is not unreasonable.

It is a worth while swap, the only minor decrease in fuel economy is easily offset by the slight additional pull that the 4.1 would help with.

 

it depends what you use the 'vert for I guess. I went from full 88 'vert drivetrain to TII drivetrain, and now instead of 3000 rpm being about 75 mph in 5th, its 65 in 5th. Im sure this isnt helping fuel economy, and it will make the car noisier on the highway. I cant really compare acceleration, cause a turbo engine went in at the same time (so it isnt really fair for the NA stuff). For me the noise isnt an issue, but im throwing it out there.

 

OK, so suppose I can have access to the entire rear of the 90 Vert., should I just pull the rear diff. or is it just as easy to go ahead and pull everything (half shafts, brakes, etc....) while I'm there?
I've done my share of old 9" Fords, but I've never pulled one with independent suspension.
Anything else I should consider getting off the car? No engine or tranny, interior almost gutted, severe body damage to front of car, etc.....

 

just swap sub-assemblies (differential and housing), the rest of the parts are the same.

 

IMO, if you are going through the trouble to switch out the 3.9 diff. for a 4.1, the end result would be better if you got an 4.1 N/A S4 LSD. I don't see the point of all that work to swap an open diff. for another open diff. where the perfomance difference is nominal.

 

Well, that was my main question: Is it worth it to go from a 3.9 to a 4.1 gear ratio?
It certainly isn't a lot of difference ratio wise, but when I had my old 87 sport model, it seemed to have a lot better ratios than this seems to have. And the transmission ratios are almost identical (5th seems to be a little taller as I recall from the specs on the 88 Vert). Of course I know it was lighter, but it seems like 1st gear is a lot taller in this car. Of course, it's been over 10 years since I had the '87, and sometimes memories seem better than they actually were!

 

You will notice a difference

 

Thanks Icemark.
By the way, I sent you a private message concerning my wiper switch.

 

As did I.

 

Ill look at PMs then, I don't always check them