Hello people! I’m looking for advise from anyone who has replaced thier rear axl. I have a built 400 making somwhere around 500 ponies. Had the tranny freshened up also. Now I need to stop the beast 😂 so ive decided to go with the Wilwood 4 wheel disk set up. I already bought the DynaPro 6 caliper drilled rotor set up for the front spindles and theyre going on this weekend. For the rear im going to order a Curries GM F-Body 9†Crate Rearend and I can order it with the matching Wilwood rear disks. The information im looking for in this post is: 1. Gear Ratio 3.50? 3.70? 3.89? 4.11? (Im thinking 3.70 but would love to hear some feedback.) 2. Open Diff? Locker? Trac Lock? 3. Because Curries builds these to order, I also have the option to shorten the axles. I dont want to “tub it†or anything, but im wondering if maybe just shorting and inch or so per side would allow me to squeez in a little more tire without rubbing?
Thanks in advance to anyone that has useful experience and can help. This is an expensive upgrade and i want to make sure I get it right. That being said, im not building a dragster and I probably wont race it but there’s nothing like stomping on it and feeling pinned in the seat!
Did I miss what transmission you have? If you have an auto TH350 or 400 I would really seariously think about not going past a 3.50 gear ratio. I say this because I have a 400 also and had a th400 in it (Tire size was 15 inch standard wheels I think about 27 or 28 inch tall) and put a second gen 8.5 rear end that was built for me by Jim at JD race and it has 3:73 gears and a Eaton tru trac limited slip and when I first ran my car with this set up in it running at 65-70 MPH it was around 3100-3200 RPM's way too much for my liking if I had to spend any amount of time running those speeds. So I decided to put a 2004R overdrive Trans in it and it dropped the RPM's down about 1100 RPM's (2000-2100 RPM's) at those same speeds. Big improvement and I actually gained more off the launch because of the first gear difference in the transmission. I really like the 3:73 gears now so unless you have a good 4 speed or higher, I would think about that unless you are already moving in that direction with the transmission. Also, I really cant tell you what the difference would be from a locker or a tru trac, I am thinking they are both about the same. Also make sure you go with some beefier axles and the currie 9in may come with thoses already. I stepped mine up to I believe it was 30 or 31 splined over the stock splined which I believe are 27 or 28 splined.
I have 3.55 gears behind my TH 400 and a nearly 500 hp 455. Responsive, but I too would like to look into some kind of tranny overdrive option with that gear ratio. The typical speed here on the freeways is 75 - 80 and I am going to get run over traveling anywhere with my setup.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
I have 3.55 gears behind my TH 400 and a nearly 500 hp 455. Responsive, but I too would like to look into some kind of tranny overdrive option with that gear ratio. The typical speed here on the freeways is 75 - 80 and I am going to get run over traveling anywhere with my setup.
No, No, No, Salmon, don't get run over!! We need your wisdom here still...LOL
Hey so yeah it’s a Turbo400 tranny. That’s great info regarding the gearing! I almost ordered the 383’s. I’m sure I would’ve regretted that. So you would suggest 3.50’s with the TracLock diff? Also yes the Currie axles are 32splined. What about the overall width. You think I could get away with shortening the axles an inch per side? I already dropped out the stock rear end and didn’t think to measure for clearance before I pulled it. 🤦ðŸ¼â€â™‚ï¸ Also I’m swapping out the leaf springs for some Calvert Racing split mono’s with track bars. I don’t think that has any relevance to my questions but I like to brag a little about my ride! Lmao. But seriously guys I really appreciate your feedback. Already helped me big time! So glad I joined this forum. 🤙ðŸ½
Hey Chris, I would for sure go with a trac lock, but just like salmon stated he wish he had an overdrive trans with his 3:55. I still think you will be running high on the RPM's Not sure if you will be doing much highway driving but I see you live in Riverside, so I would think you might to get from place to place but if not then you should be happy with that. If you are looking at a fare amount of highway driving I would go with a 3:40 or 3:30 something. With all that power you have I you will still launching good. If you have thoughts down the road about going to a 2004R or 700R4 overdrive auto Trans, then go you the 3:50 or 3:70 something gears. Just MHO. Looks like you are doing the right think for the suspension for that power you have, I would also think about putting on some Caltracs with the Calvert split monos. I have around the same power with my 400, and I while I don't have the split monos on I have the Caltracs to help with traction and supposedly they work really well. I am unsure why you want to shorten the axle and inch on each side unless you are trying to tub the back to get bigger meats under the car? If you are not doing that, I see no reason to shorten the rear end just make it the same length as the stock rear end. What size wheel/tire are you thinking about putting back in the rear?