Modify, replace, or punt

[Tenthumbs 2]

My first post and its long...sorry. OK, away we go......

New to this forum but not new to Mustangs - currently have a modified '88 LX convertible.

Recently picked up a 1969 Fastback - a replacement for the one I sold 27 years ago when I went away to college - that the PO equipped with 18x9.5" rear wheels that fit flush with the fender. Plan on lowering it about 1.5" or so which means I need a way to tuck in the wheels - even if I rolled the lip, they would not fit in the wells. Appears I need to move the wheels in about 1" per side. Current rims are Boss 338's, 18x9.5 with 4.86" offset, and 275/40zr18 tires - they look really good IMHO.

Have narrowed it down to three options and seeking opinions (never lacking on web forums):

1. Just buy some new wheels with the correct offset. Of course, that means buying all four wheels as the current make doesn't come in the proper offset for the rear; would use existing tires so they would need to be remounted and balance. ~ $1000. Punt option.

2. Having my current 9" narrowed (excellent condition, trac lok, small bearing, 28 spline axles) to 65 - 66 specs and throw in a set of 8" rear axles from the same vintage and be done. ~ $350. Mod option.

3. Put in a 65 - 66 spec narrowed rear (Quick Performance or the like) with 31 spline axles and change the carrier to accommodate 31 splines. Most likely new brakes as well since the housing ends would be different. I can sell the old rear and make back some of this money...not sure exactly how much. ~ $1400 Replace option.

I have plans on increasing horsepower (modified 351C now but an aluminum head 408C stroker is probably 3 - 5 years out) so I am leaning toward the new rear as the current one may not be able to handle the increased horsepower. Fortunately, I can do all the work, save for the narrowing part, and while finances do play into it somewhat, I want to do it right and spend the money once. Car is a street cruiser primarily but may see some trips to the strip or autocross. 

Look forward to reading the forums thoughts and appreciate all I have learned thus far by simply reading old threads....this place is a great resource with some very knowledgeable people.

[7TCatvert 24]

Wow... That's a hard one....

 

 

Random thoughts.....

 

the only other thing I think you left off is you probably will have to at least mini tub it if you narrow the rear end. Which now they make one that looks stock but gives you an extra 2 inches I think.

 

The rear end for a 408 at 450-500 horse that one you have in it now won't last long....so probably best to build a stronger unit...I am not sure I would narrow it though. The reason if you ever want to buy new wheels then you have to go back to finding that offset.

 

You could always sell the wheels on there also and make some money back...

[Rsanter 152]

Where are you located? I narrow rear ends.

I also can get you a housing and even third member that will take significant more power than the stock stuff if you think you need it

 

Bob

[Midlife 814]

With your current wheels and tires, is there at least 1" of clearance on the inboard side?  If not, shortening the rear axle is not a feasible solution.

[RPM 1,190]

Welcome to the site. But we need to see some pics brother!

[MikeStang 247]

Just went through the EXACT SAME THING your going through bud.

Here's what I had and what I did.

 

Car had a 28 spline rebuilt Posi with stock axles and Big drum brakes that all worked fine behind my 550hp 408W, but it had major traction issues.

 

I bought a 65/66 Length Housing, Axles, Rear Disc Brakes, all from Quickperformance.

The swap was easy and straight forward and fit as it should.

 

You can buy his housing and specify that you want small bearing ends and he will build to suit your needs, then you can reuse your stock axles if you like, altho I would go ahead and upgrade to some GOOD axles that will take the abuse,

I had a fellow swap my gear ratio while it was all apart and also had him inspect the POSI, since I originally did the rebuild on it and wanted it to be checked out by a Professional with a lot of EXP...  and after a year of beating on it he said it looked perfectly fine and should give me a full svc life, so dont be afraid of a 28 spline 4 Pinion Posi being able to handle the power. 

 

But the first thing you need to do is to take a lot of measurements and see EXACTLY what you need in terms of rear end length.

Those wheels should fit in there but you need to be sure you do it right and do it once... There is a 4x4 website that has an awesome wheel offset calculator on it that will help you out a TON.

[MikeStang 247]

I have the Rambler U111 17x8 in the front and 18x9.5 in the rear and the 65-66 Housing worked perfectly for me.

 

I have Drop Coils up front with about 1.5 Coils cut off , and 5-1/2 leaf Reverse Eye springs from open tracker with Cal-Track's and my car is pretty damn low.... I almost cant get my shop jack under the frame in the front LOL.

 

I have about 3/8" from the wheel on the inside to the leaf springs. I actually had 1/4" spacers on it at one time to push the wheels out but decided to remove them just because it looks fine with the rims bolted flush and gives me a little more room to the outside just in case

[moodster 55]

Really nice MikeStang, I like it a lot

 

david

[Tenthumbs 2]

Photo to give perspective. There is enough room to move the wheels in at least one inch.

 

Leaning toward changing the rear and doing some upgrades as the same time. Figure I can sell the original rear to help offset the cost.

[Tenthumbs 2]

Photo to give perspective. There is enough room to move the wheels in at least one inch.

 

Leaning toward changing the rear and doing some upgrades at the same time. Figure I can sell the original rear to help offset the cost.

[barnett468 418]

.

Don't forget to account for body sway, but 1 inch of clearance from the fender lip to the widest part of the tire should be just enough . . slightly more clearance would be better/safer . . also keep in mind that the wheel house curves in a little.

 

You will need some decent suspension for auto cross, and doing the shelby drop on the front will be a big help.

 

Expensive tires will help too but they wear fast so you might consider getting an extra set for autocross only.

 

.

[MikeStang 247]

Thanks Moodster.

 

Oh I have the Shelby drop also LOL I always forget about that.

 

Added a rear sway bar last night and lets just say with the reverse eye springs and current ride height EVERYTHING is a close fit, but I managed to get the end links vertical and not leaning... Don't know if I will see any benefits but we will see.

[MikeStang 247]

I would roll those fender lips Tenthumbs.

 

Also if you plan on going as low as I have you will need to be sure the bump stops are in place on the rear frame, especially if you go to disc brakes.

You may also want to trim that big lip off of the area where the bump stops are installed LOL.

[Tenthumbs 2]

Thanks for the advice and input!  

 

Believe I am going to do the following;  

 

- Install a narrowed rear with large bearing ends - purchase from Quick Performance - with same dimensions as a 65-66 rear

- Found a pair of 28 spline axles locally from a 66 Mustang...simply put on new bearings to match the old style ends

- Transfer all the hardware and pumpkin from the existing rear to the new one

- Since my brakes won't fit the new rear, I can either need to find some new backing plates or install rear discs

- Global West lowering rear springs with Del-A-Lum bushings

 

With the new rear, I can upgrade to 31 spline axles and new pumpkin when the time comes to modify the motor.  In the mean time, all the other components work fine and can handle the current set up.  Sort of a hybrid of the mod option.

[Rsanter 152]

Thanks for the advice and input!

 

Believe I am going to the following;

 

- Install a narrowed rear with large bearing ends - purchase from Quick Performance - with same dimensions as a 65-66 rear

 

- Found a pair of 28 spline axles locally from a 66 Mustang

- Transfer all the hardware and pumpkin from the existing rear to the new one

That will work however there is a special crossover bearing you have to use to use the early 28spline axles in a big bearing rear end

Also the backing plates are different from small to big bearing. Do you know what bearing size the exsisting housing you have is?

 

Bob

[Tenthumbs 2]

It's a small bearing end housing

[MikeStang 247]

If your getting the new housing with big bearing ends either order the rear drum kit from Quickperformance or opt for the disc upgrade for about $400.00 and call it done.

On a side note I have some of the small bearing end backing plates if someone needs them