NEW to IRS

[codycat91]

I have a 2003 GT with a 4v swap and am swapping my SRA to an IRS. I am looking on the FTBR site and don't see a phone number, so I'll ask you guys.

1.) What is the difference between the $695 and $795 dollar kit? The cheaper on has "Delrin Rear Diff Support" and the more expensive has "Delrin Isolated Rear Diff Lowering Mount". Idk what that means

2.) Will I need the shorter IRS bolts to run my current 315's?

3.) Are there any other upgrades I can/should do while the rear end is out, and while I'm ordering from FTBR?

Thanks for the responses guys!

 

[caveeagle]

1.) What is the difference between the $695 and $795 dollar kit? The cheaper on has "Delrin Rear Diff Support" and the more expensive has "Delrin Isolated Rear Diff Lowering Mount". Idk what that means

The IRS diff has 3 mounting points. Two up by the pinion, and one that is a bracket that attaches to the rear cover. Their "lowering mount" changes the position of the rear mounting point.

2.) Will I need the shorter IRS bolts to run my current 315's?

The 03/04 cobras came stock with 275/40's. I would get teh low profile bolts to be safe.

3.) Are there any other upgrades I can/should do while the rear end is out, and while I', ordering from FTBR?

replace the front two subframe bolts with 9/16” grade 8 bolt or a 14mm bolt. The factory used 12mm which was too small.

I would replace the rear diff cover with an FRP or LPW cover. For the price, its really not worth pulling it back apart to fix a leak.

 

[codycat91]

The IRS diff has 3 mounting points. Two up by the pinion, and one that is a bracket that attaches to the rear cover. Their "lowering mount" changes the position of the rear mounting point.



The 03/04 cobras came stock with 275/40's. I would get teh low profile bolts to be safe.



replace the front two subframe bolts with 9/16” grade 8 bolt or a 14mm bolt. The factory used 12mm which was too small.

I would replace the rear diff cover with an FRP or LPW cover. For the price, its really not worth pulling it back apart to fix a leak.

Appreciate the quick response. As far as the repositioned lower mount, is that something I would want? Or something that for $100 extra won't make a difference.

When I say I am new to IRS, I mean I am BRAND NEW and know basically nothing. My whole mustang life has been SRA and I know that inside and out. Honestly never even thought I would have an IRS. Are the shorter IRS bolts and the subframe bolts sold on FTBR's site? I know the IRS bolts are on AM. Is there a link anywhere to where exactly the subframe bolts are>?

Also, want to link the diff covers you referred to if you don't mind?

 

[codycat91]

Actually just noticed the 9/16ths front subframe bolts are included in the FTBR kit

 

[starnsey]

The guys at FTBR just grind down the stock bolt instead of getting the low profile bolts. The allen head bolts are very easy to strip when you have to torque them down to spec.

I swapped the IRS into my Mach (after I gave it the entire FTBR treatment) and I did not get the upgraded rear diff mount. I would say you most likely do not need it.

Diff cover:
Ford Racing Mustang IRS Differential Cover - 8.8in (99-04 Cobra) M-4033-G3 - Free Shipping!

 

[Bruha]

All I know, is you are going to LOVE it!!!! You are on the right track.

 

[caveeagle]

Appreciate the quick response. As far as the repositioned lower mount, is that something I would want? Or something that for $100 extra won't make a difference.

Honestly, unless your going super low with your car, or have some extreme angle changes to the diff, you probably don't need it. If you are keeping your angles pretty close to stock, don't worry about it. If your making a lot of changes, call FTBR to discuss it.

I used the LPW cover on my '04 cobra. Their price has gone up a little since I bought mine. I think the FRP cover comes with new bolts and does not require grinding. So for the extra $40, FRP may just be a better deal.

The LPW cover is still a very good option. Here is the link:

LPW ULTRA Cobra Mustang & Camaro Independent Rear Suspension Support Cover, IRS Differential Cover, IRS Rear End Girdle

 

[nextime]

Links to the job FTBR did to my car, yes they installed it and it was a special job cause they needed some specs for a part they sell. I went with the top end parts.

What I had installed.
FT 1350M Ford Racing Reinforced IRS Rear Diff Cover
FT 5001 Complete IRS Bushing Kit
FT 1860 Deluxe Bumpsteer/Upgraded Toe Link Kit

 

[codycat91]

There is supposedly poly bushings on it now, but if they're not FTBR should I drop the cash now and do it right

 

[GTpower01]

http://www.svtperformance.com/forums/suspension-modifications-211/231900-level-5-irs-red-pill.html

One of the best threads when moddin the IRS Tells you everything you need to support 700hp or less and what everything does....

Check it out, you can't go wrong...

FOR WHEELHOP
Listed in order of necessity/priority.
Stock to CPIE wheelhop mods

1)Billetflow Diff Cover Brace $160
2)MM Diff bushings $50 or $250
3)MMFLSFC's installed $250-300 installed
4)MM IRS Bushings $50 with 14mm bolts/nuts $15
5)Billetflow IRS Mount Brackets $50
6)Used coupe springs $50 (est) (only for verts)
7)Nitto DR $375-$425 installed

500rwhp and up
8)PHP toe link bars $410
9)Maximum Motorsports UCA/LCA Bushings $550
10)Level 5 shafts $1500


11)Strange ADJ Shocks $59ea from HBH Billetflow mount bushings $50

 

[SVTRAT]

The guys at FTBR just grind down the stock bolt instead of getting the low profile bolts. The allen head bolts are very easy to strip when you have to torque them down to spec.

I swapped the IRS into my Mach (after I gave it the entire FTBR treatment) and I did not get the upgraded rear diff mount. I would say you most likely do not need it.

Diff cover:
Ford Racing Mustang IRS Differential Cover - 8.8in (99-04 Cobra) M-4033-G3 - Free Shipping!

OP, dont grind your stock bolt. Get the low profile bolt and just call it a day. I have had my allen bolt for 7 years and never stripped it even after removing the IRS 6 times.

Good Luck

 

[caveeagle]

There is supposedly poly bushings on it now, but if they're not FTBR should I drop the cash now and do it right

Polly bushings are better than stock. (certainly better then old worn out stock)

The FTBR bushings are delrin, ar harder material that will virtually eliminate deflection.

I can tell you that replacing just the 3 stock rubber diff bushings with the MM Poly set + adding the LPW diff cover gave me a noticable improvement in wheel hop. and the 'clunk'. I would not steer you away from the FTBR kit, as that is certainly a more complete and permanent upgrade.

I did replace the front subfram bolts with 9/16", but i don't think that made too much of a difference on my car. I did not see any evidence of rub, wear, or friction in that area. I don't hammer on my car to hard, so maybe thats a factor as well.

 

[codycat91]

Perhaps I should enjoy it as is and make a winter project out of a FTBR kit and gears

 

[caveeagle]

Perhaps I should enjoy it as is and make a winter project out of a FTBR kit and gears

Nothing wrong with that strategy. If you don't mind the idea of pulling it back out in a few months. I have helped a friend install an '03 IRS into a Bullit. Really not that hard with two people and a lift.

I was just trying to fix the leaking diff, and do some 'easy' upgrades to improve the wheel hop. When I bought my LPW cover its was $180 IIRC. I considered that to be a SUPER bargain, and just could not pass up the chance to prevent future leakage. I really don't get why anyone would pay ~$130 for the bolt-on brace, when they could get the much better cover for a little more and get more case strength + the bearing cap supports to boot.

 

[nextime]

That is what I did, over the Winter I went FTBR.

Stay away from the MM stuff. If you search you will find lots of MM failures but not one FTBR failure.

 

[weaselp1]

+1 on FTBR

I did the exact same IRS install as nextime; I also put in H&R race springs and new shocks and struts at the same time. You can't go wrong with FTBR stuff, it is by far the best stuff out there; wheel hop eliminated for me after the FTBR install. :banana:

Good luck with the decision!

Links to the job FTBR did to my car, yes they installed it and it was a special job cause they needed some specs for a part they sell. I went with the top end parts.

What I had installed.
FT 1350M Ford Racing Reinforced IRS Rear Diff Cover
FT 5001 Complete IRS Bushing Kit
FT 1860 Deluxe Bumpsteer/Upgraded Toe Link Kit

 

[codycat91]

Just paid Bruce at FTBR. Also got the LPW cover. As soon as i get both, it will be game on for the swap. I'll just do it now and get it over with. Also, I believe I'll be getting the factory Bilstein shocks with the IRS and may upgrade the fronts to Bilsteins as well

 

[codycat91]

The LPW diff cover and FTBR kit should be here Monday

 

[nextime]

Does the LPW cover even work with the FTBR stuff?

 

[codycat91]

http://www.svtperformance.com/forums/driveline-216/919182-lpw-irs-cover-work-ftbr-bushings.html