THE NEW REAR IS COMING

Well, the trusty-- and crusty--12-bolt I'd purchased to replace the bent 12-bolt in my 29 Model A turned out to be a lousy benefactor for the Model T. It was no less than six inches too wide, and being well used not worth spending the time and effort of narrowing. So I've bitten the bullet and I'm buying a new 9" Ford unit from John's Industries. Mercury Charlie will be ordering it next week and the only unanswered question is what the rear end ratio should be. Seeing as the 425 Nailhead is a very torquey motor and the car is going to be well under 2500 lbs -- probably two thousand lbs. less than the car it came in -- I won't be needing a steep gear. The turbo 400 gives me three gears and no overdrive. So I need to get the rear gearing to where the RPM's are comfortable for cruising speeds, figure 65-70mph. I'd like to be taching between 2100-2300 at freeway speeds. I narrowed it down to 3.0, 3.25, or 3.50 as my options.  A quick post on the HAMB revealed the following feedback based on a 30.20" diameter rear tire (below):

2016 RPM @ 60 MPH with 3.00 gears

2184 RPM @ 60MPH with 3.25 gears

2352 RPM @ 60MPH with 3.50 gears

Considering the fact that the 425 Nailhead reaches maximumum torque at 2,800 RPM, we'll go with the 3.50 gear set which will provide the following RPM's at the speeds noted using a 30" tire:

2352 RPM @ 60MPH
2548 RPM @ 65MPH
2547 RPM @ 70MPH
2940 RPM @ 75MPH
3136 RPM @ 80MPH
3332 RPM @ 85MPH
3528 RPM @ 90MPH
3724 RPM @ 95MPH
3920 RPM @100MPH

While I'm on the subject of the rear, I've decided to go with a non-posi unit, as I'm not planning on doing any racing in it and feel that the single track nature of the rear end will be a more comfortable choice for the way I'll be using the car, which is primarily for casual cruising. It also saves on the overall cost, as a posi TruTrac would add about $900.

REAR SUSPENSION AND PROPER REAR GEARING

After talking to Charlie about the rear suspension and rear end for the T, Charlie recommended I contact Pete and Jakes to get some parts prices. I chatted with Jason at Pete and Jakes, who provided a couple of options. Charlie and I discussed those option and landed on the following set-up. We're going run ladder
bars with a 40 Ford style low-arching traverse spring. Here's a breakdown with Pete and Jakes Part #'s for the Ladder/Traverse Spring Rear Suspension:

Model A Ladder bar kit PN 2011

40 Ford style spring PN 3058

Brackets PN 5019

Rear shock kit PN 1070

Rear Crossmember for traverse spring PN3016

On Charlie's recommendation, I also inquired about rear ends with both P&J and John's Industries. 

Both Jason (@P&J's) and John (owner of John's Industries) very helpful and really took the time to base recommendations on my intended use. After discussing what I intended to do with the car, which was simply cruise it, both gentlemen encouraged "highway gears". Their rationales were almost identical. I'm building a light car using a 425 ci engine that normally came in a heavy car. Heavy cars generally were equipped with 2.75-3.0 gears. Knowing the car would be about half the weight of its original car, Jason and John both strongly advised I go with something close to factory gearing since that was what the engine was originally matched to. I based my discussions on the fact that I'd be running a 30" cheater slick. In looking at the cost differences between posi and an open rear, I was quite surprised that Jason suggested that the open rear end was a great option versus a posi. Unless I was planning on drag racing or desperately wanted to leave "twin black marks", he felt that the posi was overkill and actually might make the car less forgiving, should it break loose when jumped on. He recommended a 3.00 or 3.25 gear, so that RPMs would be in the comfotable cruising zone at highway speeds, ultimately recommending 3.25s. Having the same conversation with John, netted his recommendation to go with a 3.00 gearing so that cruising at 70 would put me in the 2000-2200 range. I was quite surprised that two such knowldgable guys would recommend freeway gears. What neither one knew is that I had a 12-bolt one-legger from a 66 Riviera at my disposal but had looked beyong it figuring I wanted both posi and steeper gearing. Wrong on both counts. We're going to go with the 12-bolt as long as its width works in our favor (It was originally purchased for my 29 roadster).

Here are the number for both gentlemen should you need some sage advice
from two guy who clearly know their rears from a proverbial hole in the ground.
Jason @ Pete & Jakes: (800) 334-7240

John's Industries: (800) 332-2450