IRS Upgrade List

[Jefe]

Planning an IRS overhaul for later this month on my 74k mile 04:

00 Cobra R Shocks
Kenny Brown springs with new isos
14mm front subframe bolts
Prothane UCA/LCA/diff bushings
Energy Suspension Subframe bushings
MM Sway Bar End Links
MM Roll Steer/Tie Rod kit
Sway bar bushings(26 or 29mm stock?)
FRPP or LPW Diff Cover(leaning towards the black LPW cover)
New axle nuts
Fuel Filter


I'm fine with the 3.55 gears and Ill be doing brakes after the summer is over. What else should I address while this is all apart?

 

[SlowSVT]

Urethane upper and lower control arms not ideal bearing material as the stuff galls and will deform under load. Delrin is a much better choice.

9/16 bolts > 14mm bolts

 

[Jefe]

Thats right 9/16, they are already on the car as well the KB springs.

Nothing against FTBR at all, but Delrin is too firm for what I want/need and I just dont buy into the belief that its either rubber or delrin. Besides, poly bushings arent all the same. The Prothane bushings have a higher durometer compared to the Energy Suspension set which is why I want those in the places that flex. A buddy of mine has been using this exact bushing setup in his IRS Cobra for 7 years and they still look brand new with no lubrication since install

Also planning on sound deadening the back half of the cars undercarriage. Roll on or spray on?

 

[jrgoffin]

Three years and counting with my Prothane bushings - still look new as well. Not one squeak and not one bit of place in the CA's. They articulate completely smooth as well. It's what can happen when you install them with the proper lube!

While you are there, I'd skip the ES subframe bushings and just stay with Prothane since they are much firmer like the rest. I would also go with the Eibach rear bar too - big difference in handling. If you can make the universal sway bar bushings work (that are the CORRECT size), that will probably help if you don't mount up the Eibach bar.

 

[Jefe]

Think Ill use this spectrum stuff from Second Skin. Helps they are based here in Tucson.

http://store.secondskinaudio.com/spectrum-1-gallon/

While you are there, I'd skip the ES subframe bushings and just stay with Prothane since they are much firmer like the rest. I would also go with the Eibach rear bar too - big difference in handling. If you can make the universal sway bar bushings work (that are the CORRECT size), that will probably help if you don't mount up the Eibach bar.

I asked him about ES vs Prothane and he recommended ES on the cradle bushings since they will transmit less noise

I haven't had the Cobra at a track day yet(6 years) so Im leaning towards not touching the sway bar right now. If I get into that Im sure Ill make the upgrade. I dont need to be taking street corners any faster than I already am lol. I need to measure my stock bar, pretty sure its 26mm

 

[AluminatorSnake]

Why dont you want the ftbr kit?

 

[Jefe]

Material firmness and price. Its a street car that has never and will never see the drag strip. Plus our city is known for having some pretty crappy roads. The less NVH the better, which is something I havent seen anyone with properly installed poly complain about.

Plus Im already running the same poly up front with no issues

 

[jrgoffin]

The '03/'04 rear sway bar is 26mm. It's 25mm for the '99/'01. As long as you don't use the Prothane bushings that are 25mm, you'll be fine. They are close, but they'll bind up the bar. It was one of the reasons poly got bashed so much - too many guys using the wrong part and having problems.

P.S. Zero noise with the Prothane cradle bushings. They come in with a Shore-D rating of about 60.

 

[AluminatorSnake]

Well i will say i just installed the FTBR kit and as far as NVH goes... i cant hear any new noise or whine over my exhaust, but there is NO vibration or harshness. The control arms move much more freely and allow the suspension to work properly. I do understand the cost, but its well worth it. My car is much smoother, more stable, and rides better than stock.

 

[SlowSVT]

Thats right 9/16, they are already on the car as well the KB springs.

Nothing against FTBR at all, but Delrin is too firm for what I want/need and I just dont buy into the belief that its either rubber or delrin. Besides, poly bushings arent all the same. The Prothane bushings have a higher durometer compared to the Energy Suspension set which is why I want those in the places that flex. A buddy of mine has been using this exact bushing setup in his IRS Cobra for 7 years and they still look brand new with no lubrication since install

Also planning on sound deadening the back half of the cars undercarriage. Roll on or spray on?

As a mechanical design engineer urethane which is an elastomer would not be my first choice for bearings material (nor my 10th). Under load the crush sleeve will distort the bushing as urethane has considerable "give". Delrin on the other hand is a self lubricating plastic which is ideal for suspension pivot points. Urethane has been used in suspension systems for decades but the main reason for using it is it's very inexpensive to manufacture parts from it because it is cast and not machined like delrin requires. I just consider it to be a harder version of the factory rubber bushings. They would be an improvement over the factory bushings but IMO are not optimal for performance.

I've seen what happens to urethane when the lubrication wears out and it wasn't pretty. It galled so bad which would have seized had it been metal. If you have good experience with them who can argue with that. The Prothane grease they sell with them is the best. That stuff stays where you put it! Petrolium grease "not-so-much". I have a grease gun dedicated to it. Nasty nasty on the hands use gloves :cuss:

Please don't dynamat your Terminator. Overtime the adhesive dries out where moisture gets trapped and starts corroding the metal. Every single car I have seen in damp climates that is getting restored is almost always rotted out under the dynamat. The stuff is heavy as well. I think I scraped out 10 lbs of the stuff just from the factory. Spray-on undercoating is even worse :nonono:

 

[Jefe]

Ordered the following. Cant wait to get this stuff on!

Bilstein E5-2959-W0
F0SZ--4B477-A(axle nuts)
Prothane 19-1182-BL
Prothane 6-1609-BL
Prothane 6-1610-BL
Prothane 6-1709(coil isos)
Prothane 6-311-BL
Energy Suspension 4.4116G
MMIRSTR-2
MMRSB-94
LPW 201-8.8IRS

 

[Tractionless1]

-I'd move the fuel filter for easier maintenance later.
-Rebuild or better yet replace the OE diff. with a Trutrack. It will never need a rebuild again as Trutrack's are maintenance free.
-Studs for your LPW cover and don't use a Lubelocker gasket, they leak. Remember you're going to have to grind the LPW insignia off that cover to clear the mount.
-Replace the pinion crush washer with a solid, helps prevent walking of the pinion into the ring gear/cover = carnage.

 

[Jefe]

-I'd move the fuel filter for easier maintenance later.

Good idea

-Studs for your LPW cover and don't use a Lubelocker gasket, they leak. Remember you're going to have to grind the LPW insignia off that cover to clear the mount.

I havent seen anyone mention this. Guess I need to look a little harder. Any links?

-Replace the pinion crush washer with a solid, helps prevent walking of the pinion into the ring gear/cover = carnage.

Also look into this, thanks!!

 

[jrgoffin]

No grinding needed with the FRPP cover. It's a squeeze, but it's a nice piece. Mine's in with the T-2R and the 3.73...

http://www.terminator-cobra.com/drivetrain.htm#Torsen_differential

 

[SVT_Troy]

-I'd move the fuel filter for easier maintenance later.
-Rebuild or better yet replace the OE diff. with a Trutrack. It will never need a rebuild again as Trutrack's are maintenance free.
-Studs for your LPW cover and don't use a Lubelocker gasket, they leak. Remember you're going to have to grind the LPW insignia off that cover to clear the mount.
-Replace the pinion crush washer with a solid, helps prevent walking of the pinion into the ring gear/cover = carnage.

When it's time I'll be more than likely copying your rear diff setup to a T. Very impressive.

 

[TRBO VNM]

Jefe,

you pm'ed me about this thread. Not sure what you want me to say? Sounds like you have it all planned out with the way you want it built. Only thing I would recommend is what others have and you shot it down. Not much more I can say.

Good luck with the build. Should be a noticeable difference.

 

[94slowbra1]

looking forward to this install and feedback. I have done a lot of research and know that delrin is a superior material for the irs bushings but is it needed? i don't track my car, auto x or drag so do i really need delrin? i do however want to upgraded the irs soon so ill be watching this. good luck on the install

 

[Jefe]

00 R shocks backordered until June and I dont want to give a penny to AMP Performance so Im going with the B8 Bilstein Shocks instead. Looks like this will be postponed until next weekend

 

[Tractionless1]

When it's time I'll be more than likely copying your rear diff setup to a T. Very impressive.

Just remember studs for the caps and cover and you're good. If I go back in I'll be upgrading to them. For now I feel it's still a significant upgrade over OE.

 

[SVT_Troy]

Just remember studs for the caps and cover and you're good. If I go back in I'll be upgrading to them. For now I feel it's still a significant upgrade over OE.

I plan on buying a spare diff case to build and have it already ready so i can take my time. I just have priorities over that at the moment like getting my new motor installed! I'll pm you when I'm ready to get the details though :beer: