Rear end suspension project

MaSnaka · #1 (**permalink**) 11-22-2011, 08:06 AM

Hey guys,
I'm getting close to pulling the trigger on my rear end replacement. Currently I have the 8" with a wore out limited slip and drum brakes. I had upgraded to the Pro-shock coilovers some time ago but with single sheer connections. I'd like to get this all beefed up to an 8.8" or 9" with the posi traction, change my ratio to 3.55 or 3.75 (currently run CR top loader with 411's) get my coilovers connected by double sheer contact points, change from drums to disc brakes.

My ultimate goal is to upgrade engine performance of my 390 which currently puts out just over 300rwhp and 370rwtq. I'm likely to get over 400rwhp with a stroker kit and new heads. But I think I need a stronger rear end first.

Well now my wheels are spinning and I'm wondering while I have the opportunity should I change the 4-link set up too? Possibly to the 3-link? I have heard the 4-link is least desirable although I'm not sure why. Has this been done to a CR before?

I would appreciate any feedback or suggestions while I develope my game plan.

Thanks,
John

bobcowan · #2 (**permalink**) 11-22-2011, 08:29 AM

The 8.8 is plenty strong enough. Unless you plan on drag racing with big sticky tires and power adders, the 8.8 will last just about forever. Using a 9" rear increases weight and parasitic loss.

For street use, stick with the stock Ford limited slip. The price and availability is good, and it's a good unit. If you're going to be road racing or autocrossing, step up to a worm gear, like T2 or TruTrak.

Double Venom · #3 (**permalink**) 11-23-2011, 04:13 AM

Ran a Tru-Trak in the Double Venom, wow.
When we went to a custom made independent rear we used an 8.8 WITH SUPPORTING COVER. DRAG raced it every weekend, speeds 133 +/- best time 11.00. No problems at all.

The simplest rear set up we found was the Stock CR set up, but changed the top arms to double adjustables (easy to change pinion angles), the lower arms are the weak point, actually flexed/ twisted under hard loads. To fix this, went to poly. bushings and totally boxed in the open arms. Cheap and certainly gets to the point in a hurry!
DV

Double Venom · #4 (**permalink**) 11-23-2011, 04:31 AM

Ran a Tru-Trak in the Double Venom, wow.
When we went to a custom made independent rear we used an 8.8 WITH SUPPORTING COVER. DRAG raced it every weekend, speeds 133 +/- best time 11.00. No problems at all.

The simplest rear set up we found was the Stock CR set up, but changed the top arms to double adjustables (easy to change pinion angles), the lower arms are the weak point, actually flexed/ twisted under hard loads. To fix this, went to poly. bushings and totally boxed in the open arms. Cheap and certainly gets to the point in a hurry!
DV

MaSnaka · #5 (**permalink**) 11-24-2011, 10:33 PM

So my shopping list includes an 8.8 with tru-trak, upgraded axles, disc brakes.

Any thoughts on the conversion idea to a 3-link vs the 4-link?

I have no track time but would like to in the future, nothing too serious. Just an occaisional weekend here and there.

Thanks so far.

John

cobraduke · #6 (**permalink**) 11-25-2011, 09:32 AM

Stay with the original four link. Plenty good. As DV said you can go to adjustable uppers and box the lowers.

Mike

Double Venom · #7 (**permalink**) 11-27-2011, 08:58 AM

Can't see a (+) with a three link?
DV

tcrist · #8 (**permalink**) 11-27-2011, 09:24 AM

John,

You can buy the adjustable thru Hodgkins(sp?). Stock Fox body replacements. I can get you the part number of mine if you decide to go that way. The might even make you some lowers if you give them the correct info. See my photos for the uppers.

MaSnaka · #9 (**permalink**) 11-27-2011, 04:05 PM

Thanks guys,
sticking with the 4-link sure simplifies things. I just thought as long as I'm at it maybe it would be a benificial change.

Terry I have the part number for those adjustable arms, you gave it to me some time ago but I have not ordered them yet. Do you know if the whole rear is set up for the stock Fox Body?

Thanks to everyone for the advice. It helps me get my thoughts straight.

I'll post as things develop.

John

tcrist · #10 (**permalink**) 11-27-2011, 05:06 PM

John,

The lowers were CR custom only but they are nothing special. They would just need to know the width of the brackets the bushings slip into and the nominal dimension between the bushings now that way they can build them with the +/- adjustment.

Double Venom · #11 (**permalink**) 11-28-2011, 04:08 AM

Hey, hodgkins are ok...but...... you sure can blow an espensive 4 wheel alignment in a hurry! They have to be "un-hooked" for any adjustment! Where as they have rear arms that have an adjustable link on BOTH ends, thus simply loosening a lock nut the arms can be adjusted simply by turning...NO dis-assembeling!

Almost always drops the price of alignment by $50.00 to $100.00.

DV

tcrist · #12 (**permalink**) 11-28-2011, 05:46 AM

DV,
Mine are just that way. Just loosen the lock nuts and spin the center to adjust. They do not have to be "un-hooked".

MaSnaka · #13 (**permalink**) 11-28-2011, 12:24 PM

DV, Terry,
are you talking about the uppers? lowers? or both? Seems to me if the lowers are not adjustable there is NO WAY to adjust alignment. The uppers only adjust pinion angle. Correct me if I'm wrong.

John

tcrist · #14 (**permalink**) 11-28-2011, 04:03 PM

John,

I am talking about my uppers. I left the stock (but strengthened) lowers.

The lowers will adjust the wheel base and the uppers will adjust the pinion angle. Actually they both can adjust both somewhat. DV is correct about being careful though.

YerDugliness · #15 (**permalink**) 11-28-2011, 04:29 PM

Quote:

Originally Posted by MaSnaka

DV, Terry,
are you talking about the uppers? lowers? or both? Seems to me if the lowers are not adjustable there is NO WAY to adjust alignment. The uppers only adjust pinion angle. Correct me if I'm wrong.

John

I think you're right, John.

Here's the way I heard it:

The lower arms set the wheelbase length.

The upper arms set the pinion angle.

The panhard rod sets the left-right positioning.

Should be easy with modern alignment shop equipment, I'd think.

My bars have locknuts on both ends, too....loosen them and then turn the center section to make your changes. Don't forget to tighten them back up, though. The last time I was under the Cobra I had probably put 500 miles on the new bushings, so I checked the locknuts and found two that were loose. I don't know how much spontaneous rotation there might be, but at any rate it can't be good.

There is a member here who has offered to help me if I need help adjusting mine, so if you're hung up by something let me know and I'll run it by him.

Cheers!

Dugly

MaSnaka · #16 (**permalink**) 11-28-2011, 04:48 PM

My lowers are a nice solid aluminum piece but they are only 14" bolt to bolt. So my rear tire sits towards the front of the wheel well about an inch off center. So I will need the proper length lower arms as well. I'll get this all sorted out soon enough, I've only had my car on the road for 7 1/2 years. Hopefully I get this done in January '12. Thanks again for all the input.

John

tcrist · #17 (**permalink**) 11-28-2011, 05:16 PM

John,

Mine are about 14 1/2 center to center on the bolts and my tires are fairly centerd on the wheelwell.

MaSnaka · #18 (**permalink**) 05-09-2012, 07:19 PM

OK, Low and behold...I have things moving in a favorable direction. My gallery has been uploaded with some pictures of my progress. Parts are being powder coated now so maybe in two weeks I will have everything put back together (wishful thinking). I purchased a new 9 inch rear end from Currie and since they were out of stock on the traditional style housing I got upgraded to the Fab-9 housing at no extra charge. This thing is sweet! I have adjustable upper and lower control arms (lowers were modified for length). New Wilwood 11" brakes to replace my drums. New master cylinder and proportioning valve. Beefed up the coilover/shock mounts to a double shear connection which will give me some piece of mind back there. Ended up getting a 3.70 gear ratio and the TruTrack posi and 31 spline axles. Everything looks to be bullet proof and stout. I am getting rather excited to get back on the road, hopefully before months end. Thanks for all the helpful advise.

John

MaSnaka · #19 (**permalink**) 05-28-2012, 09:44 PM

Project update...Well as hoped for my project was completed and I was back on the road last week. I drove the car to a highly referred frame and suspension shop here in the San Fernando Valley for my final 4 wheel alighnment and pinion angle set. The job took just under 1 1/2 hours and the mechanic said things were just slightly off but I can't tell the difference in the way the car drives. It's nice to know that everything is correct. The ride in the rear is noticably softer with a lot less bounce. I think the old assy must have been binding at some point. The new rear disc brakes work good and look awsome compared to my old drum brakes. Coilover mounts are in double shear top and bottom which greatly improves the strength and my confidence on the rough stuff. I do hear a little whinning noise from the Tru-Track periodically and on spirited launches the car goes straight where before it would pull to the left. I have absolutely no more chattering clutch. I noticed a crack in my trans cross member and had a new one made which should never bend or crack again, this may have been contributing to some of the chatter I experienced. Some new pictures in my gallery with some detailed views. On to the next project now.

John

D-CEL · #20 (**permalink**) 05-29-2012, 08:21 AM

Hey John,

It all looks great! Excellent work!

Jason