Looking for a new Ford 8.8 IRS

priobe · #1 (**permalink**) 03-02-2009, 08:37 AM

Does anyone know if the you can purchase a IRS 8.8 brand new from the dealer?

Also, can you order it in a specific gear ratio?

blykins · #2 (**permalink**) 03-02-2009, 08:42 AM

You just wanting the hog's head, or are you looking for half shafts and everything?

priobe · #3 (**permalink**) 03-02-2009, 08:55 AM

just looking for the Hog's head.

I wanted to go with something new with 3.27 gear or 3.31 gear.

I wanted to price out the difference between replacing my gear / labor vs buying new.

blykins · #4 (**permalink**) 03-02-2009, 08:59 AM

Ah...

If you check out Ford Racing's catalog, you can see what they offer.

A new set of FRPP 3.27 gears would probably be about $150. I have a guy here that charges me $150 to set them up, but I guess it just depends on who's available in your area.

My guess is that you will have a lot less in the gears/labor than for a complete IRS hog's head.

blykins · #5 (**permalink**) 03-02-2009, 09:01 AM

Check this out:

http://cgi.ebay.com/ebaymotors/Ford-...4506.m20.l1116

Jegs sells the pumpkin just by itself for $569....so to add gears and a differential would be a lot more.

My best guess is that you'd be better off to snag a set of gears and have someone do the install.

priobe · #6 (**permalink**) 03-02-2009, 11:14 AM

Yeap I guess your right.

For some reason I thought it was made $200 difference between new and replace.

Any one running a BB with toploader and ?? for gears.

dont know if I should go 3.08, 3.27, 3.54

blykins · #7 (**permalink**) 03-02-2009, 11:33 AM

You can use a rpm/gear ratio calculator and figure out where you'd be at different speeds.

I had a '73 Corvette with a Muncie 4-speed. With 3.55 gears, it was just fine on the interstate. As a matter of fact, I drove it for 6 hours on interstate from Louisville to Cleveland.

My vote would be 3.55 gears.

priobe · #8 (**permalink**) 03-02-2009, 11:41 AM

@ 3000 rpm that puts me at 62 mph (3.55) I am not too sure about that

I am leaning toward 3.31 (non Fors Motorsport gear) or 3.27 FMS

I have heard to stay with a FMS if changing the gear.

priobe · #9 (**permalink**) 03-02-2009, 11:43 AM

Also, I wonder if I will have to realign the car because I think I will have to drop the rear spindles to get the halfshaft out.

Does anyone know with a EM IRS

blykins · #10 (**permalink**) 03-02-2009, 11:44 AM

Be sure and use a calculator that includes your tire height. It makes a big difference.

I always use FMS gearsets in my stuff. Richmond gears have a tendency to whine, even when set up correctly.

I would buy either Motive or FMS, and my installer says that the FMS gears are the higher quality of the two.

I'm getting about 66mph with a 3.55 and 26.6" (295/50/15) tires.

priobe · #11 (**permalink**) 03-02-2009, 11:54 AM

Great.... nothing is ever easy

The 3.31 gear is Motive and the 3.27 or 3.55 is FMS.

Ford does not make a 3.31 damn it decision decision.

I was prefering 3.31.

I did you the calc for tire size which is 25 in.

Here is the breakdown at 60 mph

Keep in mind I am currently at 3000 rpm @ 60 mph = 3.73

1. 2500 rpm @ 60mph = 3.08
2. 2650 rpm @ 60mph = 3.27
3. 2700 rpm @ 60 mph = 3.31
4. 2900 rpm @ 60 mph = 3.55

blykins · #12 (**permalink**) 03-02-2009, 12:21 PM

I don't see 50rpm being any difference whatsoever between gears. A few psi tire pressure would probably make that much difference.

Something must be up with the calculator.

You're saying that you're currently at 3000rpm at 60mph with the 3.73's, but the 3.55's are only 100 rpm different.....while the 3.27/3.31 gears are 50rpm apart?

Jerry Clayton · #13 (**permalink**) 03-02-2009, 12:25 PM

Put a tko 5/600 or t56 in it and keep the rear you have

Jerry Clayton · #14 (**permalink**) 03-02-2009, 12:27 PM

Brent

Have you used any of the SFI 427 Q/T housings???? We had the first one and some issues, wonder if they got the changes made to the production ones

Jerry

priobe · #15 (**permalink**) 03-02-2009, 12:56 PM

great ,

I tired a different calculator and I am getting different numbers.

Does anyone have a good calculator for the rear gear.

priobe · #16 (**permalink**) 03-02-2009, 01:06 PM

ok here it is from another calc.

3.27 = 2565 rpm - 60 mph
3.31 = 2600 rpm - 60 mph
3.55 = 2785 rpm - 60mph
3.73 = 2930 rpm - 60mph

undy · #17 (**permalink**) 03-02-2009, 01:53 PM

3.27 FMS gears for a 25" tire height and a Top Loader is the way to go. 3.08s will work too if you don't have much cam. They will will give you a nicer cruise RPM.

Dave

Three Peaks · #18 (**permalink**) 03-02-2009, 02:14 PM

Why not just go to the more standard 26.5" tire and/or replace the r&p with the 3.27 gears? Should get you right where you want to be and have plenty of power off the line also.

olddog · #19 (**permalink**) 03-02-2009, 04:13 PM

Quote:

Originally Posted by priobe

Great.... nothing is ever easy

Keep in mind I am currently at 3000 rpm @ 60 mph = 3.73

If the above numbers is dead accurate for your car, forget the calculators and just multiply out the ratio of the gear ratios.

3000 * new ratio / old ratio
or
3000 * 3.55 / 3.73 = 2855

1. 2477 rpm @ 60mph = 3.08
2. 2630 rpm @ 60mph = 3.27
3. 2662 rpm @ 60 mph = 3.31
4. 2855 rpm @ 60 mph = 3.55

Another important thing to consider is the speed limits that you drive in. If you are taching 2477 @ 60 mph you will have 1651 at 40 mph. Depending on your cam, it may not run there and it will force you down a gear. That could put you back up to 3000 rpm in order to run 40 mph. You want to make sure that it is pleasant to drive where you run the most, not just 60 mph.

priobe · #20 (**permalink**) 03-02-2009, 04:32 PM

olddog,

Excellant point. Next time I take the car out I will monitor low rpm and at what speed.