Author Topic: Trying to Fit a 315 in the Rear  (Read 3131 times)

Offline WildJones

  • Jr. Member
  • **
  • Posts: 227
Trying to Fit a 315 in the Rear
« on: May 02, 2016 - 02:39:39 PM »
Well this weekend was both exciting and a disappointment. Finally at the stage in my build where I can test fit wheels on the car before I order them (for custom BS). My goal was a 295 square setup, and with a 1" Dr Diff relocation in the rear, I was almost dead certain that the rear would be trouble free while I would have to compromise for a 275 up front.

Wheel specs and spacers I had available:
18 x 10.5 +38mm
2x 1 inch spacers
2x 3mm spacers

Let's start with the rear, we test fit the driver rear first. The wheel fits like a glove and I am feeling confident. Tried the passenger rear and tire hits the leaf. Wheel off, add a 3mm spacer, try again. Tire still hits the leaf. Wheel off and add another 3mm spacer. Tire still hits the leaf. Found a 1/4" spacer (I think) from a Camaro in the shop and tried that in place of the 2x 3mm spacers. Tire still hits the leaf. Add in the 2x 3mm spacers to the mix and guess what? The tire is still hitting the leaf. :pullinghair: There wasn't enough wheel stud at this point to add anymore spacers without moving to a 1" spacer that adds studs. I did not test fit because the clearance to the fender was already tight so I figured it was a waste of time.

At this point I was really disappointed/frustrated so we moved to the front. Surely I am going to be disappointed here too, right? Wrong! I was able to fit the 295 in just fine, with possibly enough room for a 315. What??? I've been stressing the front tire fitment for nothing? With a 1 inch spacer behind the wheel, from lock to lock I had three fingers of free space from the edge of the wheel to the frame on both sides. On my hand, that's 1 3/4" of space. There was about an inch of space from the outside of the wheel to the fender lips (not rolled).

Here's what I learned this morning after talking with the shop and giving him some numbers that I was able to pull off the web from the site: the axle is shifted about 3/4" to the driver's side. Keep in mind, I already had the shop weld new perches on when I did the 1" relocation. Its my fault for not telling them to make sure that it was centered under the car. So now I am wondering what to do. Here are my 3 options as I see it:
1. Run smaller tires (boooo!). The 275 out back just looks small.
2. Get the Dr. Diff 1.5" relocation kit. This will hit the rear valence since I have Hotchkis springs and create a dimple. My paint is likely to pop up and crack (it has done it on other spots of the car). I'm not sure if the paint could be color matched or what the added cost would be.
3. Buy either the RMS Street Lynx or the XV Stage 2 rear end. I think I need the 1.5" relocation kit for the RMS or weld in the brackets on the inside of the frame rail for more clearance?

Intended purpose is obviously for traction and the reason for a big tire up front is because I want good handling and because I can fit it. Can anyone give me some recommendations to get a 315 or a 295 minimum in the back?
Mike
95682
1970 Cuda




Offline RCman

  • Jr. Member
  • **
  • Posts: 33
Re: Trying to Fit a 315 in the Rear
« Reply #1 on: May 02, 2016 - 09:11:16 PM »
What about cutting off the perches and starting over with them centered under the car? Perches are cheap and it shouldn't take all that long to cut off the incorrect ones and weld up some new ones. Off by 3/4" sounds like a lot though.
You would have to do that anyway for the 1.5" kit.

Offline Chryco Psycho

  • Administrator
  • C-C.com Guru
  • *****
  • Posts: 36620
  • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
Re: Trying to Fit a 315 in the Rear
« Reply #2 on: May 02, 2016 - 10:07:38 PM »
 :iagree:
 This is where i would start

Challenger - You`ll wish You Hadn`t

Offline GoodysGotaCuda

  • Sr. Resident
  • ******
  • Posts: 5392
Re: Trying to Fit a 315 in the Rear
« Reply #3 on: May 02, 2016 - 10:10:17 PM »
What about cutting off the perches and starting over with them centered under the car? Perches are cheap and it shouldn't take all that long to cut off the incorrect ones and weld up some new ones. Off by 3/4" sounds like a lot though.
You would have to do that anyway for the 1.5" kit.

Same conclusion I came to reading it.
Build Page: Goody's 'Cuda Build Page
1976 Dodge Warlock
1972 Barracuda - 5.7 Hemi + T56 Magnum

Wheel & Tire Specs:Link

Offline YellowThumper

  • Sr. Member
  • ****
  • Posts: 1633
  • I left the snow for this?
Re: Trying to Fit a 315 in the Rear
« Reply #4 on: May 03, 2016 - 01:25:16 AM »
Yep gotta center it first...
Removing the warning labels one at a time.
Nature will take care of the rest.

Offline WildJones

  • Jr. Member
  • **
  • Posts: 227
Re: Trying to Fit a 315 in the Rear
« Reply #5 on: May 03, 2016 - 12:22:01 PM »
Thanks folks for keeping me sane and logical. I picked up 1.5" relocation shackles (the front mounts are the same between the 2 kits supposedly - I'll confirm with Cass) and 2 new perches. We will center the axle and test fit with the 1.5" relocation kit and see where I stand from there. As awesome as the Street Lynx kit is, it's a little expensive for me at this point, and I already have the Hotchkis rear setup. That's going to be my last resort.
Mike
95682
1970 Cuda

Offline RCman

  • Jr. Member
  • **
  • Posts: 33
Re: Trying to Fit a 315 in the Rear
« Reply #6 on: May 03, 2016 - 03:00:46 PM »
My 1.5" kit from Cass had 1" offset front mounts so that sounds correct.
Also when I lined everything up it did not come out to 44" center to center as some mention. Probably because of the front mounts but IIRC it was closer to 44 7/16" center to center on my perches. I actually only noticed the front mount offset because of that; when I checked everything after it was tacked before I final welded it up I noticed it wasn't 44" and wanted to discover why.

Once you line everything up under the car that will really tell you where they need to be.
« Last Edit: May 03, 2016 - 03:03:54 PM by RCman »

Offline cudabob496

  • Sr. Resident
  • ******
  • Posts: 8024
Re: Trying to Fit a 315 in the Rear
« Reply #7 on: May 03, 2016 - 06:24:55 PM »
what brakes up front?
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

2011 Kawasaki Z1000

Offline brads70

  • C-C.com Expert
  • ********
  • Posts: 18747
Re: Trying to Fit a 315 in the Rear
« Reply #8 on: May 03, 2016 - 06:41:57 PM »
Jason has a nice post he created on this . Did you see it?
http://www.cuda-challenger.com/cc/index.php?topic=79257.0
Brad
1970 Challenger 451stroker/4L60 auto OD
Barrie,Ontario,Canada
Proud to own one of the best cars ever made!!!!!

My restoration thread 
http://www.cuda-challenger.com/cc/index.php?topic=59072.0
 My handling upgrade post
http://www.cuda-challenger.com/cc/index.php?topic=73985.0

Offline WildJones

  • Jr. Member
  • **
  • Posts: 227
Re: Trying to Fit a 315 in the Rear
« Reply #9 on: May 03, 2016 - 09:07:31 PM »
what brakes up front?

Dr Diff Stage 4. They push out the wheel a little further.

Jason has a nice post he created on this . Did you see it?
http://www.cuda-challenger.com/cc/index.php?topic=79257.0


Brad,

I read that awhile ago but didn't think to reference it. Thank you for reminding me!
Mike
95682
1970 Cuda

Offline dodj

  • Sr. Resident
  • ******
  • Posts: 6197
Re: Trying to Fit a 315 in the Rear
« Reply #10 on: May 03, 2016 - 11:05:41 PM »
Using the 1.5" Dr Diff kit and re-welding the perches, I fit 315's in my car. The BS on my wheels are, if I remember right, 6". I'm about 1/2" from the springs and clear the quarters with no rolling.  :2cents:
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline WildJones

  • Jr. Member
  • **
  • Posts: 227
Re: Trying to Fit a 315 in the Rear
« Reply #11 on: May 04, 2016 - 12:18:13 AM »
Using the 1.5" Dr Diff kit and re-welding the perches, I fit 315's in my car. The BS on my wheels are, if I remember right, 6". I'm about 1/2" from the springs and clear the quarters with no rolling.  :2cents:
Excellent news! What wheel width are you running? 18s too?

I've heard that Challengers have more space out back than Cudas. Any truth to that statement?
« Last Edit: May 04, 2016 - 12:22:24 AM by WildJones »
Mike
95682
1970 Cuda

Offline dodj

  • Sr. Resident
  • ******
  • Posts: 6197
Re: Trying to Fit a 315 in the Rear
« Reply #12 on: May 04, 2016 - 02:21:39 PM »
Excellent news! What wheel width are you running? 18s too?

I've heard that Challengers have more space out back than Cudas. Any truth to that statement?
The rear wheels are 17x10.5. Tires are Nitto 315ZR35. Rubber ends up about 12.5" wide.
As for more room than a 'cuda, I don't know anybody with a 'cuda locally to check.
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline jordan

  • Full Member
  • ***
  • Posts: 601
  • no replacement for displacement
Re: Trying to Fit a 315 in the Rear
« Reply #13 on: May 05, 2016 - 09:46:29 PM »
My cuda has less room on the passenger side than the drivers side.  I welded my perches equal to the axle ends.  I thought about centering the rear axle housing in the car but was worried that it would cause a drive line harmonic problem.  With all of the fussing over a degree or two for the pinion angle, what is the potential problems by moving the pinion to the side by 3/4 of an inch?  Does that work into pinion/driveshaft angles too; not in the up down plane, but in the side to side plane?
"Don't brake until you see God!"

Offline WildJones

  • Jr. Member
  • **
  • Posts: 227
Re: Trying to Fit a 315 in the Rear
« Reply #14 on: June 24, 2016 - 10:47:30 AM »
Guys, question about centering the axle. Right now, the driver side of the axle has about 1/2 inch more room on the axle, pushing the driver side wheel out 1/2 more than the passenger side, but the pinion on the diff lines up straight with the output shaft on the tranny. 

So when you say center the axle, do you mean center it so that the driveshaft is straight, or center it so the ends of the axles are equal from side to side (so wheels protrude the same amount)? In talking with my friend who owns the shop, he thinks I should keep the driveshaft the same so as to reduce the likelihood of vibrations by shifting the center.

Fwiw the axle is offset enough that you can notice by looking at the back of the wheel to the mounts and notice that things aren't straight. Maybe just because I'm focusing on the rear end like I am right now.
Mike
95682
1970 Cuda