Okey Dokey.

Here is my Dilema.

I did a front end swap on my 56 Ford F-100. I swapped a 1996 Crown Vic front end on that has disc brakes but the smaller bolt pattern. In the rear I left the 9" I had back there with the drum brakes. Mainly becuase it was much easier. Leaf sprung with sway bar.

Here are my problems

#1: Two different Bolt Pattern sizes I need two different wheels and it makes it hard to carry a spare (I don't even have a place to put one)

#2: Rear end ratio and traction. I currently have an open diff...I need to go out and jack it up but if I remember correctly the ratio is very low as in 2.55 or something like that (good for mileage on the highway). I have yet to drive the truck (this weekend the first time ever) so I'm not sure how the ratio will drive on the street.

So should I throw the 8.8" under it that I got from the crown vic? It has 3.55 gears and a limited slip. It also has disc brakes (stops great anyway so I don't think it really matters). This way I have good traction and the designed gear ratio for the transmission (P71's at least) and I take care of the bolt pattern issue.

Or do I go with a currie axles, re-gear and stay with the 9"?

I just don't know. The 8.8" makes the most since but everyone I've talked to seems so darn proud of the 9" as it is a classic I understand. But the 8.8" is more than tough enough and considering the spline count is higher in the new 8.8 "I believe" it is probably a storonger axle anyway.

Ohh and I can put disc brakes on the back (I have the old front discs from the front)..I would just have to make a new backing plate).

Ok that is a lot to digest but I appreciate any input. Go 8.8 (way cheaper...aka besides spring perches free) or with the 9".

 

I vote to go with the 8.8 as it matches up the wheel lug pattern and works with the driveline you have.

The 9-inch is overkill for the motor you have. Besides, you can get a good price for it.

 

the nice thing about the 9" rear is that you can have a couple of different pumpkins around with different ratios to suit your plans. going for a long hiway cruise, swap in some 2:73 or 3:1 pumpkin. day at the track or street cruising, swap in some 3:5, 3:73 or even 4:11 ratios. swapping the pumpkins on a 9" is probably one of the easiest things you could do. messy but fairly easy.

any competent machine shop in your area should be able to redrill your axles to the new bolt pattern. i did mine in our machine shop at work. just make sure to take the rim you are going to use along also so if they have to machine the register to fit your rim as the truck register is usually larger than the car register.

that being said the 8.8 is a very good rear and you won't go wrong using that one either. toss up as to what is going to be easier, modify the 8.8 to fit your truck (weld on spring perches, set pinion angle, hook up emergency brake lines, etc) or modify the 9" axles to fit.

either way you are going to have a good strong rear end to work with.

Rgds
Mike

 

im parting an 87 vic for the discs for my 53 as well as many other things , and also have the 5x51/2 9 inch rear under the bench i was gonna put in it . the vic's 8.8 diff is the right width , matching bolt pattern to the soon to go on discs , and in my case im going from a 32 gear to a 2.73 in the 8.8 . i actually get to exceed the speed limit if i desire and a hoped for improvement in fuel mileage ! the t89 four gear has an ultra low first that should allow it to take off like it has a mid 3 in the diff , therefore not killing my flatty , and 4 th should be like an overdrive . go with the 8.8 .

 

Certainly a lot cheaper to use the 8.8" you already have it, it's the right ratio, and has disk brakes as a bonus. To use the 9, you'll need to at least redrill the axles, backing plates and drums (not just the axles!), and buy a new R&P and used pumpkin with a limited slip. If you think the 9s are dear wait until you start pricing LSDs for one, IF you can find one. the 8 is more than strong enough to handle anything < 500 HP in a pickup with street tires IMHO.

Oh yah, as another bonus a lot bigger selection of wheels are available in the smaller pattern.

 

Disc Disc = different Brake master cylinder than Disc Drum ?
Drive shaft length ?
Shock attachment?

 

Yes, but interchangable so just a bolt in swap, can eliminate proportioning valve as well.

? May fit, Length should be close, there are hybrid U joint trunions available in different length/bearing cup diameter on each pair of arms if needed.
Duplicate whatever is there. If the shocks attach to a stud on the lower spring mount plate like mine just swap them over.

 

I'd vote for keeping the nine inch and having the bolt pattern changed unless you are running an AOD tranny. How the truck drives with the 2:55 rear gear will depend somewhat on what tranny you are using. If it's an AOD your OD will probably be next to useless. I ran an OD tranny with a 3:00 gear and it did not work as well as you might expect. If it's a three speed automatic without OD it should work fine although it will be a bit doggy on take off. I'm running a 2:26 gear with a three speed automatic and it's fine for cruising as well as decent gas mileage. If you are running an AOD the 3:55 gear in the 8.8 will be a lot friendlier...

 

Thank you all very much for the input. I'm not sure if I'm any closer to a decision but at least I am armed with a lot of good information.

As to some of the info given I'll give some more updates.

Regarding brakes I used the brake master cylinder from the crown vic and left out all of the anti-lock brake mechanisims. I put a proportioning valve on to the rear drums already. If I went to different axle shafts in the rear I would buy new rotors or drill the ones I have and use my old calipers from the old front end to get disc brakes. So I would not need to do anything with the Drum brakes that are on there.

As to the width of the axles I believe they are withing an inch of each other.

Yes shock attachememtns and Sway Bar would have to be fitted as well with the 8.8

I already chopped up my driveshafts and made a hybrid with my old shaft coupled in the front with the Crown Vic joints.

I do have the AOD transmission from the crown vic.

With the work that has been done I should have just gone with the 8.8 in the first place. I just don't have the money to make the 9" like I would want it to be.

 

Depending on which 9" rear you have, 8.8 Explorer discs bolt right on.

 

Since you are using the AOD you definitly do not want to run a 2:55 gear. The 3:55 or even something shorter yet like a 3:70 would be much better.

 

Well, which ever you go with, those 2.55 gears are going to make you a dog off the line. Might be nice on the freeway, but its going to take forever to get going in town.

I vote for the 8.8

 

Edit,

I jacked it up today and it is 3.00 gears (as close as I can tell by spinning it) and it does appear to have a limited slip.

Took it for its first test drive today. Having problems with the transmission shifting into 3rd and overdrive....As in not at all.

Lots of tweaking to go. A little doggish off the line but considering I can't get enough traction without my bed anyway I'm not to worried about the gearing for now.

 

It should shift into 3rd regardless of the 3.00 ratio. The OD I ran with a 3:00 gear shifted into OD at about 60-65 MPH but it would stay in back down to 45. You may have a problem with the transmission or perhaps the TV cable is not adjusted properly. Do not drive the truck until you get the TV cable adjusted correctly. You can burn up a transmission quick with the wrong adjustment!

 

It is electronically controlled. I think it might have something to do with the wiring and the PCM...anyone out there smart on these things. Might have something to do with my lokar shifter.