Mustang/Ford experts...hop right in

Marty Howard · **Posted:** Tue Jul 27, 2010 3:03 pm

So I am playing around with swapping rear gears from event to event. Right now the Spec series dictates I run 2.73 so I need to keep those, but for non spec races and the other stuff I think I want to run either the 3.08 or 3.27 to keep the car most in prime RPM for 3rd and 4th VS the 2nd and 3rd combo now. The rear is a stock Ford Mustang 8.8.

So the question is:
Would it be easier to change the ring and pinion or just keep a separate diff to swap between each event? Cost is almost the same either way.

Vincent Keene · **Posted:** Tue Jul 27, 2010 3:14 pm

If you change the R&P won't you have to set (and reset) the pre-load each time? Sounds like a pain.

Jason Mauldin · **Posted:** Tue Jul 27, 2010 3:30 pm

Vincent Keene wrote:

If you change the R&P won't you have to set (and reset) the pre-load each time? Sounds like a pain.

From what I understand, the Pre-load spacing "usually" follows the housing, not the R&P.

Marty Howard · **Posted:** Tue Jul 27, 2010 3:37 pm

One issue is the 8.8 is part of the housing, so it maybe a full axle swap vs just a diff swap.

here was a neat suggestion:

Quote:

Well, if you have a complete 2nd diff setup (including the LSD assuming you are using one) then swapping the diff isn't that hard.

Put together two complete ring and pinion setups and keep each setup complete, including the bearings and shims. You can then pull the bearing caps, drop out the whole diff out the back. The alternate unit goes right back in without any setup, just put everything back.

As long as you keep everything together its a fairly easy swap. We used to do this on the Old Moto Cup Mustangs. I could do a swap in under an hour without trying to hard.

WalterHouston · **Posted:** Tue Jul 27, 2010 3:40 pm

Jason Mauldin wrote:

Vincent Keene wrote:

If you change the R&P won't you have to set (and reset) the pre-load each time? Sounds like a pain.

From what I understand, the Pre-load spacing "usually" follows the housing, not the R&P.

Jason is correct.

However, I can swap rear end in and out of my Camaro in 1 1/2 hours by myself. Personally, I'd buy as second rear end with the gear ratio I wanted and a good dif (I like Auburn) and swap the whole assembly when I need to change.

Swapping out carriers, ring gear and pinion gears is a pain and would take longer. You would need new gear oil every time, a new pinion seal in front and possibly a gasket for the rear cover. It isn't so bad out of the car, but much harder to get it right under the car.

Kevin Harvey · **Posted:** Tue Jul 27, 2010 4:08 pm

First, I wouldn't go through that much effort. I'd leave the spec rear in it and shift the crap out of the tranny. But I am lazy.

Second, I would buy a second rear end and do an entire swap versus messing with the gears.

Marty Howard · **Posted:** Tue Jul 27, 2010 4:16 pm

Kevin Harvey wrote:

First, I wouldn't go through that much effort. I'd leave the spec rear in it and shift the crap out of the tranny. But I am lazy.

Second, I would buy a second rear end and do an entire swap versus messing with the gears.

One of the issues I have with the 2.73 is running out of RPM before track out. The 3.27s are a nice middle ground that puts the 3 - 4 shift at 12 mph higher than the current 2-3 shift. Plus it's a straight shift vs a cross pattern shift.

DickRasmussen · **Posted:** Tue Jul 27, 2010 4:50 pm

Marty Howard wrote:

Kevin Harvey wrote:

First, I wouldn't go through that much effort. I'd leave the spec rear in it and shift the crap out of the tranny. But I am lazy.

Second, I would buy a second rear end and do an entire swap versus messing with the gears.

One of the issues I have with the 2.73 is running out of RPM before track out. The 3.27s are a nice middle ground that puts the 3 - 4 shift at 12 mph higher than the current 2-3 shift. Plus it's a straight shift vs a cross pattern shift.

Any chance the rules allow a change to the Ford 9" with its removable fully setup complete diff assembly (i.e. carrier)? :lol:

(just joking).

Kevin Harvey · **Posted:** Tue Jul 27, 2010 5:23 pm

Marty Howard wrote:

One of the issues I have with the 2.73 is running out of RPM before track out. The 3.27s are a nice middle ground that puts the 3 - 4 shift at 12 mph higher than the current 2-3 shift. Plus it's a straight shift vs a cross pattern shift.

Which track and which turns?

Kevin Harvey · **Posted:** Tue Jul 27, 2010 5:25 pm

And how are the 3.27s going to have a numerically higher mile per hour shift point? It should be lower than the 2.73s.

Are you running out of "breath" with the 2.73s from not enough power or running out of rpm?[/quote]

Marty Howard · **Posted:** Tue Jul 27, 2010 5:27 pm

Kevin Harvey wrote:

Marty Howard wrote:

One of the issues I have with the 2.73 is running out of RPM before track out. The 3.27s are a nice middle ground that puts the 3 - 4 shift at 12 mph higher than the current 2-3 shift. Plus it's a straight shift vs a cross pattern shift.

Which track and which turns?

turns 1-2 combo, 11, and 14 at CMP.

1-2 Combo and Oak tree at VIR.

I can do then in 3rd, but it puts the RPM at about 2100/2500 and the engine bogs with the 1.33 3rd and 2.73 combo.

Marty Howard · **Posted:** Tue Jul 27, 2010 5:30 pm

Kevin Harvey wrote:

And how are the 3.27s going to have a numerically higher mile per hour shift point? It should be lower than the 2.73s.

Are you running out of "breath" with the 2.73s from not enough power or running out of rpm?

its not for the same gear, it would be the 2-3 combo for the 2.73 vs the 3-4 combo for the 3.27

Karl Shultz · **Posted:** Tue Jul 27, 2010 9:19 pm

If you're stuck with the gears you don't like when you're racing the car, I would absolutely NOT change them. I'd drive with them every single event. It'll teach you how to better manage shifting in places you don't like. That's just me.

RichardNuss · **Posted:** Wed Jul 28, 2010 7:39 am

Karl Shultz wrote:

If you're stuck with the gears you don't like when you're racing the car, I would absolutely NOT change them. I'd drive with them every single event. It'll teach you how to better manage shifting in places you don't like. That's just me.

Karl has a very good point.

But if you do want to swap, I'd swap entire axle assemblies. How is it set up in your car? I'm assuming 4-link and disc brakes? If so, you're looking at removing the d-shaft, 4 link mount bolts (plus bolt for panhard bar if you have one), lower shock bolts, coil spring retainers (if you have them), and unbolting the brake calipers from the axle.

To make the swapping easier, you could build (or buy somewhere?) a mount for on top of a floor jack so that the pumpkin sits on it, and it also grabs the axle tubes.

I used to crew on a 4-cyl Mustang oval-track car, and we needed different rear gear ratios to be fastest at different tracks. We swapped whole axles. It was a little more trouble because we had drum brakes so had to bleed them each time. (We also swapped transmissions for different tracks to get different trans gear ratios, but that's a different story.)

Marty Howard · **Posted:** Wed Jul 28, 2010 8:14 am

Karl Shultz wrote:

If you're stuck with the gears you don't like when you're racing the car, I would absolutely NOT change them. I'd drive with them every single event. It'll teach you how to better manage shifting in places you don't like. That's just me.

That's a good point. A really good one.

Richard,
It's a 3 link system with a Panhard. Disc brakes as well.

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