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gear swap and the IRS on the 99-01 cobras

9.6K views 14 replies 7 participants last post by  01SVTCobra  
#1 ·
Thinking about going with 3.73's or 4.10's on my 99 cobra. I would like to keep the IRS. Is it a problem? Can I get to the gears without removing the whole IRS. Are there speed shops in Pennsylvania anyone knows about near reading/allentown that can handle it? Thanks!
 
#3 ·
I remember reading an article a while back that the IRS makes the gear swap more challenging- it might have been in MMFF. But they actually had to cut something out, but they probably were swapping the IRS out as well.
Does anyone know if shops charge more for these cars?
 
#6 ·
Anyone know of capable shops in the reading, PA Area?
 
#7 · (Edited)
Tony,

I just got a quote for a 3.27 ---> 4.30 gear swap in my '01 Cobra yesterday from Hartman Driveshaft & Axle located at 315 George Street in Reading (near the Fairgrounds mall). His shop rate is $65/hr and he estimates it will take 6 hours to do the swap.

Originally I was going to take it to Kevin Mc Curdy's garage in Shartlesville, PA - who did a great job on my '89 Mustang GT gear swap, but he said he didn't have the tools for an IRS swap and recommended Hartman's. I was also considering SGS Automotive (formerly Kauffman's Motorsports) but they also charge $65/hr so why travel that far when there's a place closer that will do it for the same price. Plus Hartman's guys called me back :) and sounded knowledgable and friendly. Hope this helps.

PS save yourself the mistake and go 4.30's. Research will show that any less isn't recommended for our Cobras.
 
#8 ·
If it is at all possible save yourself some $$$ and remove the pumpkin yourself and take it into the shop to have gears installed.

This next bit is VERY important if the shop is unfamiliar with IRS diffs. In most solid axles there are c-clips that hold the axles in place, the IRS doesn't have these. The IRS halfshafts are held in the diff with circlips.

Despite the IRS not having C-clips the 3/4" diameter steel C-clip retainer pin is still in the new diff. IRS and solid axles use the same 8.8 differential. The shop that did my gear swap didnt mess with the center c-clip pin since it was not used. Only problem is that this pin has a small bolt through it that when tightened secures the reatiner pin in place. It was not torqued down.

If this hadnt been caught and fixed by myself the small bolt could've come loose and then 3/4" pin wouldve fallen out of the diff partially contacting the diff housing and more than likely lock the rear end up instantly and the brand new T56 I just installed as well. Either way it wouldnt be pretty, so make sure that bolt is tightened, even if it means that you have to pull the diff cover off to inspect that the bolt was tightened.

Hopefully, this will help someone out because this was discovered until I had my car all back together. Pulling the rear cover off while the Diff is in the car wont happen, I had to tighten the bolt with a 1/4 flexible extension through the 1/2 gap of the diff and diff cover. >:p
 
#9 ·
Ramnstang,

I am confused. I thought you said the shop you used didn't mess with that center c-clip pin, but somehow the bolt in it was not torqued down by the shop?

Redfox,

Thanks, let me know how it goes and what the final cost is. Where did you buy the gears from and how much. Did you buy only the gears or the "gear kit"?
 
#14 · (Edited)
Ramnstang,

I am confused. I thought you said the shop you used didn't mess with that center c-clip pin, but somehow the bolt in it was not torqued down by the shop?
Exactly, the shop didnt tighten the bolt and the diff comes from the factory with that bolt just finger tightened in place. Reason that the bolt is loose from the factory is that the center pin will have to be removed when installing the axles and c-clips in a solid axle, the retainer pin is slid back into place and the bolt is torqued down securing the reatiner pin in the differential. On an IRS this step was overlooked since the center retainer is not used. A pic would really help explain what Im talking about.
 
#10 · (Edited)
The final cost will be $400 - I wouldn't be happy with anything higher especially since that's the going rate AND that's what he quoted me for. It's going to be a little more expensive for me though because I have a leaky CV boot and will most likely need to have my half shaft replaced. The good news is, that most of the work with the half shaft would have already been done during a gear swap.

The gears I'll most likely get off eBay. I want a new set of 4.30 FORD racing gears and I've seen them going for just under $200 shipped. I'll then have to buy the gear kit and the gear oil. I will probably be doing this at the end of this month.

What color is your Cobra? I see a Black one around with a huge 2000 Cobra R style wing on it, is that you?
 
#11 ·
Not me. Mine is a black coupe with tan interior, stock wing, stock rims. She drives just like the day I bought her, 23,000 miles.

The guy that does my car inspections recomended Hartman as well- do you think the hartman guys would let you be in the shop watching while they worked?
 
#12 ·
You'd have to ask them Tony, but I don't think they would have a problem with that. They sounded so nice. I don't blame you for wanting to do that, either. Six hours is a long time to be at a garage, though.

Here's my car:

http://wagner.gotdns.org/cobra
 
#13 ·
Your car looks great. The wing was different for the 01's. In looking at your pics, it reminds me to get my car lowered, they look like there is enough room between the fenders and the tires to take a nap in there.

Let me know how the gear swap goes- I am concerned because my car drives so well that I'll end up with vibrations, whining from the gears, etc.- and I am not planning on taking it to the track so ? the need for the gears.

My e-mail is licataa@yahoo.com.
 
#15 ·
$400 for the install on an IRS is real cheap for near me. The only good shops get about $600 to $650 and package the deal with ring and pinion, lube and rebuild kit at about $850 on an IRS car. They usually drop the rear of the IRS subframe to pull the pumpkin and then the gears. Alot worse than the straight axle job.

BTW 4.10 and deeper are the norm with the 4v motors, most dont step up to the 3.73
svtperformance dot com has a bunch of people who have done the swap to deep geats in a NA 4v cobra