About to Order Springs CC Plates and Rear Diff Bushings

[351stang]

After a long period of leaving the Cobra alone, I've started driving her more often. I changed jobs and no longer have to drive an hour in stop and go traffic each way. I've just got to drive 4 miles. I've also started to go to a local car show once a month.

The differential has been leaking for awhile, so I've finally decided to pull it and fix it properly. I decided to do a couple other things at the same time and would appreciate any pre-purchase feedback:

1. H&R Race Springs w/ MM Poly isolators
2. Maximum Motorsports Urethane IRS Differential Mounts
3. Maximum Motorsports 03-04 Cobra Caster Camber Plates - Chrome

I am not ready to do all of the IRS bushings. The car already has MM full length subframe connectors, air bags in the rear springs, billet flow brace, and the IRS front bolts have the larger bolts.

Is there anything that I should reconsider purchasing or consider doing while I'm in there (ie balljoints)? The car has 85,000 miles.

 

[Kyle_KleinSS]

If you are pulling the entire irs I would do all of the bushings. I have zero wheelhop. If you are just pulling the diff, which imo is stupid, at least do the diff bushings. You can have the entire irs out in about 30-60 minutes. I would just pull the whole assembly. Do it once do it right. Also ditch the brace and get the Ford Racing cover.

 

[351stang]

Is a $250-300 cover really an upgrade over a stock diff with a girdle?

 

[Woody6799]

I agree with Kyle on the bushings. You can do all MM or "Prothane" Poly bushings in the IRS for pretty cheap and I love them. I did the full kit and it tightened up the car a lot. As far as the leaking diff I would def go with the FTBR pre milled Ford Racing Diff cover. The factory piece is just crap. While you are in there you should do your fuel filter as well. Your IRS will be fresh and ready to be abused. And as long as you are in the area I would simply inspect all rubber bushings and consider replacing with poly.

 

[Kyle_KleinSS]

I would definitely do poly if you cant swing delrin. You can buy the kit for less than a few hundred. And yes on the diff cover. Few still leak even with the brace. However, if you do the poly diff bushings, you dont need the milled cover. You can save some coin there. The milled cover is only needed with Bruces kit. I like poly on the diff, I dont want it locked solid. I have poly diff bushings, and delrin everywhere else. No hop

 

[KyleSVT]

Spend the money on the Full Tilt stuff. Its worth it
http://www.svtperformance.com/forums/showthread.php?1076133-Full-Tilt-Boogie-Racing-03-Cobra-IRS-Kit-Before-Install-and-After-Videos&highlight=

 

[Woody6799]

I would definitely do poly if you cant swing delrin. You can buy the kit for less than a few hundred. And yes on the diff cover. Few still leak even with the brace. However, if you do the poly diff bushings, you dont need the milled cover. You can save some coin there. The milled cover is only needed with Bruces kit. I like poly on the diff, I dont want it locked solid. I have poly diff bushings, and delrin everywhere else. No hop

I prefer the Poly personally, and second, I would go with the milled cover just in case you ever change things up in the rear and need it milled. For the price difference its worth the flexibility.

Spend the money of the Full Tilt stuff. Its worth it
http://www.svtperformance.com/forums/showthread.php?1076133-Full-Tilt-Boogie-Racing-03-Cobra-IRS-Kit-Before-Install-and-After-Videos&highlight=

I prefer poly, I don't want to be riding on plastic and 99.9% of the guys on here that go FTBR never use it the way it was intended. It is a track oriented set up. Save some money and save a little ride quality and go poly. If you track it, go ftbr.

 

[351stang]

I ordered H&R springs, MM CC plates, MM diff bushings from MM.

I broke down and bought a non-milled Ford Cover from Summit Racing for $247 shipped.

I'll report back in a couple weeks.

Thanks for the input.

 

[bubblehead93]

I started with poly diff bushings and now have the MM aluminum (solid) diff bushing setup since I have a Fore diff cover. I think if your going to seriously do the 1320 with an IRS you need solid diff bushings (slicks, 2-step, etc). That is just my experience. If your going to principally street the car with only the occasional 1320 blast then poly will be fine. Based on what you described as the principal use for the vehicle (street & shows), poly should serve you fine.

 

[Jefe]

Is a $250-300 cover really an upgrade over a stock diff with a girdle?

No question, its worth it. I dont think anyone has broken an FRPP/LPW cover yet.

I would not piece meal this job. Do it all at once and get it over with. By far the biggest project I ever did on mine and it was worth every penny:

http://www.svtperformance.com/forums/showthread.php?1008284-IRS-Upgrade-List

 

[351stang]

Install Question

Ok, so I've read the Ford Shop Manual and MM's instructions, but I'm not clear on the best way to install the rear springs while I'm dropping the differential.

1. MM Rear Spring instructions say to loosen the front IRS Subframe bolts, remove the rear IRS subframe bolts, and slowly drop the IRS subframe until the springs come out. (I simplified this and didn't write all the intermediate steps)
2. The differential bushing/drop the differential instructions say to compress the rear spring slightly to move the lower control arm front bushing bolt in (not out). This is with leaving the spring in place.

I am wondering what sequence I should do the rear springs. Should I do them first? Should I do them after removing the half shafts? Should I do them last while the silicone is drying?

I'll do the front springs and CC plates after the diff is out and the RTV is curing.

[I am not removing the whole IRS, but now I understand while it was suggested]

 

[Kyle_KleinSS]

Put them back in when swinging it back up. Why are you trying to loosen the control arm bolt??

 

[351stang]

I'm pulling the diff to reseal. The differential cross member bolts to the front lower LCA bolt where it meets the subframe.

 

[351stang]

I just dropped the springs first, then the diff. I'll reinstall the new springs when I go back together.

The threads on one of the back IRS subframe bolts are toast. It's the first time I've ever removed that bolt, so I guess I have Ford or some Ford Tech to thank for that. Anyone have a PN handy?

I also found that Brake Check had put the wrong rear brake caliper pins in. They were too small on the "head" and could rotate freely, thus the caliper bolts were barely tight. It's been like that for 2 years, so I'm glad I found it.

I had to stop work, so I won't get it back together until next weekend.

This is the bolt that stripped:

 

[Kyle_KleinSS]

I dont recall the crossmember bolt on the lca. ID have to look. The shock bolt yes. The bolt thats sripped just replace that with the mm low profile bolts. Thats all it is