Rear End Build Plan

[CompBCurrie]

My Trac Loc just gave up on me so I'm going to upgrade my rear end. What do you guys think about this plan?

31 Spline Trac Loc Diff from an F150 w/ Carbon Fiber Clutch rebuild kit, stock F-150 3.73 gears and Moser Axles. 3.73s because I like how relaxed the car is on the highway and I eventually plan on a procharger or eaton. I go to the local 1/8mi strip every other weekend and plan to run ET Streets at the track and 275 or 315 drag radials on the street.

I've also been looking at the Centerforce DFX clutch because I doubt my stocker will hold up to much more abuse (45k miles mixed hwy/ city, a dozen quarter mile passes, 20 1/8 mile passes). Has anyone had a bad experience with a DFX?

[o3BlueMach1]

first of all i would say its not worth it to go to 3.73's from 3.55's, at the minimum i'd do 3.90's... second, i havent used the dfx clutch but i have used the centerforce dual friction clutch, ill give it a 7/10 just because it is rather noisey clutch because of the weights on the pressure plate that rattle, but it has no chatter and has withstood around 50 passes at the track without a hiccup...

[CompBCurrie]

I read a post on here that said 3.90s whine, plus I'm getting the F150 diff with the 3.73 ring and pinion for 135 bucks.

[Jester]

I don't think any particular ratio gearset is going to make noise. I've been through five gearsets with my Mach and the only one that didn't whine was the stock 3.55s.

You definately need to go with a rebuildable unit like the Ford part you mentioned. With all those passes on that diff you should be taking your car in yearly to get the rear serviced and checked by your mechanic.

[Thor]

Originally Posted by Mach1Marauder

4.10s at least with the Procharger.
You can get by with 3.73 with the Eaton.

Good choice on the diff.

Agreed. In my case with the ProCharger, I'm flirting with dropping from 3:55 to 3:08 due to specific driving application needs - which is simply location.

[Stopsign32v]

Originally Posted by Thor

In my case with the ProCharger, I'm flirting with dropping from 3:55 to 3:08

Your car would be amazingly slow unless you plan on trying to reach 300mph. A Procharger motor lives off of RPMS. I cannot think of any good reason to go with 3.08 gears at all from a performance point of view.

[one mach 1]

Originally Posted by Thor

Agreed. In my case with the ProCharger, I'm flirting with dropping from 3:55 to 3:08 due to specific driving application needs - which is simply location.

I think with 3.08's you will lug the engine with a redline clutch dump on street tires!!

[CompBCurrie]

Thanks for the input...I need to find somebody who has 4.10s so I can ride in their car on the hwy and see if I can live with it.

3.08?! What's the deal with where you live that you'd like them better?

[CompBCurrie]

I just found an even better deal on a diff and gears from a local pull-your-own junkyard. 1994 explorer 31 spline trac loc with 3.73s...$49.99. Now lets see if they're torn up when I get them out.

[Mach1Nut]

I understand your thoughts about not wanting to go with a taller gearset because you like how it cruises with the 3.55's, but believe me, the DOHC engine likes to rev. I have 4.56's and don't regret them one bit. I cruise around in 5th gear at about 2,650 on the freeway doing 70 (where with the stock 3.55's it was 2,000 rpm @ 70mph) and it hardly feels any different. In fact, it actually feels much better than before because I don't have to downshift to speed up to pass, etc... Also, I can now cruise around at city speeds (40-45) in 5th gear and I have not seen a noticable drop in gas mileage other than long highway drives.

4.10's would probably be perfect for a Procharger or Eaton if you stay below 500rwhp. So, in my opinion, at minimum, get 4.10's. You won't regret it, and if you don't get a supercharger for a while, you'll wish you went taller!

[o3BlueMach1]

Originally Posted by one mach 1

I think with 3.08's you will lug the engine with a redline clutch dump on street tires!!

He wants 3.08's cuz he is in germany.... next to the autobahn ....

[jbrad88]

I am getting mosers and a built 31spline truck posi installed Friday. I am keeping my 4.10's for now without going any more agressive. These gears are perfectly matched (IMHO) to our cars for the street. These engines need rpm to make power and the 3.55's although a very good gear, did not do it for me.

I would not drop down to a 3.08 either. These engines, unlike the pushrod motors before them, don't make the low end torque. You could have a 2.73 or a 3.08 gear behind a 302 because it was a tractor engine in comparison. Gobs of low end torque...

[CompBCurrie]

Everyone keeps saying 4.10s, 4.10s...so I'm going to compromise and start looking at 3.90s. That will keep my 4th gear usable to 135 (not that i would ever use that as a law abiding citizen) and be a little more fun while the car is N/A.

BTW I plan on doing this install myself but for sh*ts and giggles I called around for prices. I just got a quote for $560...with me providing the diff, ring and pinion, and install kit....NOT including the labor for the Trac-Loc rebuild. I laughed at the guy and got hung up on. Another shop wanted $375 and another shop 3 hrs away wanted $250 (very reasonable, I think, but far away).

[one mach 1]

Originally Posted by CompBCurrie

Everyone keeps saying 4.10s, 4.10s...so I'm going to compromise and start looking at 3.90s. That will keep my 4th gear usable to 135 (not that i would ever use that as a law abiding citizen) and be a little more fun while the car is N/A.

BTW I plan on doing this install myself but for sh*ts and giggles I called around for prices. I just got a quote for $560...with me providing the diff, ring and pinion, and install kit....NOT including the labor for the Trac-Loc rebuild. I laughed at the guy and got hung up on. Another shop wanted $375 and another shop 3 hrs away wanted $250 (very reasonable, I think, but far away).

Get the 4.56's! Don't fear the gear! You will be doing your car a disservice by not getting the gear that keeps it in its power band while getting on it. It pulls like a freight train with the 56's!!