'54 IHC R-110 differential

Gentlemen,
I am "resto-moding" a 1954 R-110. Plans include an '85 Mustang 5.0L with the Tremec T-5 five speed from the same Mustang. Plans are to replace the front suspension with a Fatman (or equivalent) M II conversation as the original leaf spring/I-beam axle suspension is trashed. I would like to keep the original IHC differential and 4.10 gearing. However, the brakes are probably inadequate for the increased power of the Mustang V8. Additionally, the original parking brake was on the output shaft of the transmission therefore, there is no provision to add parking brakes to the original backing plates. My dilemma is, try to find a backing plate/brake assemblies with parking brakes and drums to fit the IHC axle or just pony-up and get a modern axle that will fit?

Any suggestions, advice or recommendations will be appreciated.

Bill
Noblesville, IN

I think you'll save a lot of headache just upgrading to a newer axle.

95+ Ford Explorer has an 8.8" rear end with factory disks and is the same lug pattern. About the same width also. Can be found a few different ratios and limited slip also.

Sounds like you’re doing what I did 10 years ago. I choose a SBC 383 stroker, 700R4 trans for power but the rear end became a 9” Ford approximately 60” wide, as best I recall. I got mine with disc brakes including internal emergency brakes. I purchased an emergency brake kit from Lokar and connected up to the original emergency brake handle. Like you I put Fatman Fabrications MII kit under the front end. I started out with the air ride option, but a few years ago deleted it in favor of adjustable coil over shocks. The air ride was always leaking down during the week when I wasn’t driving the truck and then I needed to wait for the system to pressure up before I could drive. That just got to be too sloppy for me, so deleting the air ride corrected it. Any of the modern rear ends, assuming from a donor with comparable power source, should serve you sufficiently, unless you’re going to do a lot of racing. If that’s the case, Ford 9” rears are proven to be head and shoulders above the rest, but you’d also already know that.

If you do not up-grade everything, you will regret it. The OEM rear differential will not handle the torque from a V8 5.0. .
Check out WEW51L110 truck build and follow his lead. What he did was simple and reliable.

Thanks all. I'll start looking for an 8.8 in. or 9 in. with 4.10 gears. I'm thinking I want to put 265/70R16 tires on it so the 4.10 gears will work with the OD on the T-5 to keep the RPM down at highway cruising speeds. I'm not looking for a race car but at 73 I still like to "punch it" once in a while!

It has turned out that the 8.8 is a strong differential. The only advantage with a ford inch is the removable center section. 8.8s are available with disc brakes. An 8.8 is much less expensive than the 9.
4:10 gearing is a little les common. I do not know your needs or wants, but I think you might consider a much more common 3:73 ratio. I ran 3:73 in my R120 for two decades and 225,000 miles. I installed a Gear vendors overdrive behind a Ford C6. The R120 was able to cruise at 75mph. The top speed was just over 90 mph.

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IHNUTZ, obviously you can select whatever gear ratio suits your fancy. Faced with making that decision, I found some websites that offer calculators to help make that decision. Like you I wanted my tranny to have overdrive to reduce highway revs and that’s what I got with the 700R4. I have 17” wheels with 29.5” diameter tires. I’m the same age as you and I apparently like the thrill also of punching the accelerator to get that push back into the seat feel. Having 4:10 gears, even with an overdrive tranny, is not going to reduce the highway revs as much as you think. Once I went through the calcs, I settled on 3:50 gear ratio. My 70 mph revs are at about 2500 and although I don’t often break traction on WOT, I do get that push back into the seat I’m looking for. If I were going to do occasional drag racing, 4:10 or steeper would be a real consideration, but a steep gear ratio will have your engine “racing” at highway speeds. I’m putting premium gas in my 10:1 compression motor, and the mpg is around 12, even with the 3:50 rearend and OD trans. I shutter to think what it would be if I had higher ratio rear. I drive to lots of shows, and at 12 mpg it takes roughly a tank of gas to get to each one and back home. Like I said, you can do as you desire, but do so based on being educated about what you’re deciding.

if you are upgrading engine I'd upgrade rear end too, I've snapped a few axles in 50s trucks with a stock 220.

WEW51L110: Thanks for your advice. My choice of 4.10/4.11 gears comes from wanting to run 265/70R16 tires (30.6"). With the T-5 fifth gear OD at .68 that brings the "calculated" engine RPM down to <2200 at 70mph and <1700+ at 55mph. The RPM difference between 3.55 and 4.11 gears is aprox. 250 to 300 RPM between 55 and 70mph, respectfully. I think I would rather keep the cruising RPM closer to the rated, advertised torque specs of the stock Mustang 5.0 considering the increased size and weight of the R-112 compared to the Mustang. Too low RPM at cruising speeds can hurt fuel mileage as much as too high RPM, especially with a carburated engine. Not arguing, just my opinion. Besides this project is still in the development/planning stage, I still can change my mind.