Rear Suspension and NASCAR 9" for 71 Javelin Project

[Bulletpruf]

Fellas -

Working on a budget 71 Javelin road race/street build - - Trans Am type car with minimal creature comforts, 450ish hp 401, close ratio T10. Cage is done (Piper Motorsports) and time to start on rear suspension.

I think I'm going to stay with a leaf spring rear suspension for now for simplicity and affordability. Likely will use fiberglass rear springs. May upgrade to a 3 link at a later date.

Choices on rear diff are making my head hurt. My options, in order of preference:

1. For about $1250 + shipping, I can get a used NASCAR 9" rear with housing by Speedway or Tex Racing, used center section (3.50 gear, Detroit Locker), used Currie 31 spline axles (full floater, 5 on 5 bolt pattern), used hubs, 1.5 deg negative camber both sides (is this about right?), 3 degree down pinion angle (is this about right?). I can get this with or without the pump; not sure if I need one for road racing (NASA American Iron).

2. Original AMC 20. Currently one-legger with 3.15 gears and the factory two piece axles. Would need 3.54 gears (about $100 used), Detroit Locker ($500), axles ($400). Very limited and expensive ($800) disk brake options and don't have the ability to swap center sections for a quick gear change.

3. New Moser 9" - $3,200 with TrueTrac, 31 spline axles, nodular case, no brakes. That would blow my budget.

I like the price on the NASCAR rear, and I can use inexpensive stock car brakes. One problem is that the NASCAR rear is 58" and my stock rear is 55 7/8" (I forget whether that's axle flange to axle flange or if it's just the width of the bare housing) so it's at least 2 1/8" wider. If it's not too far off, I can fix this with wheel offset.

If the width works, I think the rear would be pretty much ready to go; just grind off the existing brackets, weld new spring pads, add brakes and I'm good, right?

Anyone have any experience or input?

Thanks!

Scott

[exwestracer]

Check Speedway or Summit for their 9" circle track floater kit. I just saw one somewhere for $699 including axle shafts and discs (no 3rd member). If you're going to stick with leaf springs, add a pair of slide-a-leafs and a torque arm. Plenty of low-buck ways to mount one to the 9" snout.

(Found it: http://www.speedwaymotors.com/Grand-...rend,6587.html)

[Bulletpruf]

Check Speedway or Summit for their 9" circle track floater kit. I just saw one somewhere for $699 including axle shafts and discs (no 3rd member). If you're going to stick with leaf springs, add a pair of slide-a-leafs and a torque arm. Plenty of low-buck ways to mount one to the 9" snout.

(Found it: http://www.speedwaymotors.com/Grand-...rend,6587.html)

Thanks. Only issue is that these are in 58" and 60" widths. Sent an e mail to see if they could go narrower.

Scott

[Bulletpruf]

Check Speedway or Summit for their 9" circle track floater kit. I just saw one somewhere for $699 including axle shafts and discs (no 3rd member). If you're going to stick with leaf springs, add a pair of slide-a-leafs and a torque arm. Plenty of low-buck ways to mount one to the 9" snout.

(Found it: http://www.speedwaymotors.com/Grand-...rend,6587.html)

Any sites or books that I can reference for leaf spring tech? I'd like to do this in my garage so I could use some detailed info.

Thanks,

Scott

[Bulletpruf]

Check Speedway or Summit for their 9" circle track floater kit. I just saw one somewhere for $699 including axle shafts and discs (no 3rd member). If you're going to stick with leaf springs, add a pair of slide-a-leafs and a torque arm. Plenty of low-buck ways to mount one to the 9" snout.

(Found it: http://www.speedwaymotors.com/Grand-...rend,6587.html)

One more question - wouldn't I be better off with a panhard bar? From what I'm reading, looks like the shortcoming of a leaf spring car is the lateral movement, which would be controlled with a panhard bar.

Thanks

Scott

[exwestracer]

One more question - wouldn't I be better off with a panhard bar? From what I'm reading, looks like the shortcoming of a leaf spring car is the lateral movement, which would be controlled with a panhard bar.

Thanks

Scott

Scott, a torque arm controls pinion movement and wheel hop, which you will have under acceleration and braking, esp if you convert to fiberglass monoleaf springs. Yes, by all means use a panhard bar as well. The watts linkage IS a better choice for a leaf spring car, but MUCH trickier to mount because of the springs extending back from the axle.

[Bulletpruf]

Scott, a torque arm controls pinion movement and wheel hop, which you will have under acceleration and braking, esp if you convert to fiberglass monoleaf springs. Yes, by all means use a panhard bar as well. The watts linkage IS a better choice for a leaf spring car, but MUCH trickier to mount because of the springs extending back from the axle.

Thanks, Ray. Good info.

Scott

[Motorcitydak]

Better would be a watts link rather than a panhard bar. I got a moser circle track rear axle, cost $1000 to my door for whatever width I wanted. Its a full floater, 5x4.5 or 4.75 (your choice, has holes for both). You can use tons of different cheap bolt on brake rotors and just make up a bracket for the calipers. Grab a 3rd and you are set. I don't suggest a detroit locker tho, its action is a little rough and not something Id want in a road car. Im going to use a tru trac in mine.

[Bulletpruf]

Better would be a watts link rather than a panhard bar. I got a moser circle track rear axle, cost $1000 to my door for whatever width I wanted. Its a full floater, 5x4.5 or 4.75 (your choice, has holes for both). You can use tons of different cheap bolt on brake rotors and just make up a bracket for the calipers. Grab a 3rd and you are set. I don't suggest a detroit locker tho, its action is a little rough and not something Id want in a road car. Im going to use a tru trac in mine.

I realize that the Watts link will be superior, but I'm leaning towards the panhard because it looks like it will be a bit easier to install.

Will check out Moser's circle track rears. Did you have them add some camber or toe? If so, what specs?

Thanks

Scott

[Bulletpruf]

Better would be a watts link rather than a panhard bar. I got a moser circle track rear axle, cost $1000 to my door for whatever width I wanted. Its a full floater, 5x4.5 or 4.75 (your choice, has holes for both). You can use tons of different cheap bolt on brake rotors and just make up a bracket for the calipers. Grab a 3rd and you are set. I don't suggest a detroit locker tho, its action is a little rough and not something Id want in a road car. Im going to use a tru trac in mine.

I realize that the Watts link would be a better choice for controlling lateral movement, but leaning towards the panhard bar b/c it should be a bit easier to install.

I'll check out Moser's circle track rears. Did you give them specs for camber or toe? If so, what did you go with?

Thanks

Scott

[Motorcitydak]

I realize that the Watts link would be a better choice for controlling lateral movement, but leaning towards the panhard bar b/c it should be a bit easier to install.

I'll check out Moser's circle track rears. Did you give them specs for camber or toe? If so, what did you go with?

Thanks

Scott

I got it with no camber at all, made em straight up since Ill do a lot of road miles with this car. I want normal tire wear

[AMC Racer]

Used Nascar rears and Summit rear likely have a centred pinion. Not sure on Speedway? IIRC, the AMC pinion is offset 9/16" or so to passenger's side, so likely need a custom housing. Another option is to get 9" housing ends or ends & tubes on your AMC 20, to give lots of brake options and bigger bearings, since you'll be getting custom axles anyway. Long term, the 9" is likely the better choice. Assume you're running a fuel cell? If stock tank, doubt a Watts will fit ... a panhard is a tight squeeze.

[Bulletpruf]

Used Nascar rears and Summit rear likely have a centred pinion. Not sure on Speedway? IIRC, the AMC pinion is offset 9/16" or so to passenger's side, so likely need a custom housing. Another option is to get 9" housing ends or ends & tubes on your AMC 20, to give lots of brake options and bigger bearings, since you'll be getting custom axles anyway. Long term, the 9" is likely the better choice. Assume you're running a fuel cell? If stock tank, doubt a Watts will fit ... a panhard is a tight squeeze.

9" housing ends would be an upgrade for the AMC 20, but gear changes would still be painful. I also have a 66 Fairlane GT convt with a 9" - can swap out the chunks easily - this one has a 3.25 gear, TrueTrac, 31 spline.

Will check on the pinion issue.

Hadn't planned to run a fuel cell; was going to run a sump off the stock tank. However, no big deal if I have to go with a fuel cell.

Thanks

Scott

[Bryce]

Check out my watts link build.

I built a watts link because I could not afford to have any lateral tire movement.

[Bulletpruf]

Check out my watts link build.

I built a watts link because I could not afford to have any lateral tire movement.

Hey Bryce - you know what page the Watts link build is on?

Thanks

Scott

[Bryce]

Hey Bryce - you know what page the Watts link build is on?

Thanks

Scott

Look at post 882 for installed pictures.

post 664 and 539 has an assembled picture.

post 442 455 shows build up

[Bulletpruf]

Look at post 882 for installed pictures.

post 664 and 539 has an assembled picture.

post 442 455 shows build up

Man, that is some very nice fab work! I'm going to have to read the whole build thread now. Anyway, your Watts link setup looks like a work of art, but too much going on there for me. I'm looking for something that I can do in my garage that won't take me a few months to figure out. I can get an adjustable panhard bar kit for not too much $ and really doesn't look like much welding will be required to install it.

Thanks

Scott

[AMC Racer]

Check the links showing panhard installs on AMCs (none mine). Note the tight fit to the tank on the AMX ... fitting a Watts would be a challenge? An adjustable panhard like Penske Javelin seems ideal. You can get brackets, bar, links etc. from most circle track places, so just need to make the chassis mounting bracket.

Allison Powered 1970 AMX racer
http://i207.photobucket.com/albums/b...od807004-1.jpg
http://i207.photobucket.com/albums/b...od807002-2.jpg

70 AMX modified Mustang kit:
http://theamcforum.com/forum/panhard...551_page2.html
http://www.maierracing.com/pnms2202a.html

Penske Javelin (note the adjustable panhard, full floating AMC 20 with hoses from differential housing to an oil cooler, heavy springs with stock location & reversed front spring eye to lower the rear, stock lower alxe/spring/u-bolt bracket modified to fit end links for sway bar and stock staggered shock locations with adjustable shocks). Seems this may be a reasonable way to go with mostly stock-type parts and mounting locations.





Hope this helps.

[Bulletpruf]

Check the links showing panhard installs on AMCs (none mine). Note the tight fit to the tank on the AMX ... fitting a Watts would be a challenge? An adjustable panhard like Penske Javelin seems ideal. You can get brackets, bar, links etc. from most circle track places, so just need to make the chassis mounting bracket.

Allison Powered 1970 AMX racer
http://i207.photobucket.com/albums/b...od807004-1.jpg
http://i207.photobucket.com/albums/b...od807002-2.jpg

70 AMX modified Mustang kit:
http://theamcforum.com/forum/panhard...551_page2.html
http://www.maierracing.com/pnms2202a.html

Penske Javelin (note the adjustable panhard, full floating AMC 20 with hoses from differential housing to an oil cooler, heavy springs with stock location & reversed front spring eye to lower the rear, stock lower alxe/spring/u-bolt bracket modified to fit end links for sway bar and stock staggered shock locations with adjustable shocks). Seems this may be a reasonable way to go with mostly stock-type parts and mounting locations.

Hope this helps.

Duane -

Man, that's exactly what I was looking for! Lots of interesting items to see on the Penske pics.

Thanks!

Scott

[TXSZ66AVLANCHE]

I googled "used narcar rear end" to see if anyone else has taken on a project using a retired Narcar housing, I started my project in July on a 95 S10 to road race on open track days @ Eagle Canyon Raceway, looks like lots of good information on pro-touring.com