szalkerous

iTrader: (1)

Question regarding geometric setup on the rear of the 4th gen cars....

I have a FAYS2 Watt's Link setup that I'm trying to get installed with a reinforced rear-end cover (JUST the diff cover, no arms or anything) There doesn't seem to be enough clearance between the frame bar of the watt's link and the rear diff cover, so the propeller binds against the cover.

My intended solution was to install single-adjustable rear LCA's and an adjustable TQ arm. However, the LCA's only adjust about 1/2-3/4" shorter than the stock fixed length LCA's.

So now I'm falling into geometry hell trying to adjust the TQ arm's upper adjustment, and the LCA's to get the rear end more forward in the car (the tires were sitting too far to the rear after the TQ arm install anyhow), and making sure I can get a -2* pinion angle on the diff.

All the while I'm concerned about the performance characteristics of shortening the driveline, even by an inch. Will that cause any problems with the driveshaft or handling?

I tried reading through the book I generally refer to, "How to make your car handle", but it doesn't really touch on this subject. Advice or references to a good literature piece are very welcomed. Thanks in advance.

-Sz

pewter2002

iTrader: (4)

I have the Watts with a Mac rear end girdle installed. Although it is close, I have no clearance or interference whatsoever. The girdle is very thick at the perimeter, probably an inch thick.

Is it possible that something isn't installed correctly?

szalkerous

iTrader: (1)

Totally possible, although I'm usually very meticulous about this sort of thing. I think when I put in the adj. TQ arm it pushed back on the rear end... When I put the rear wheels back on and let it down on the ramps to check clearances, the rear wheels sat noticeably towards the rear of the wheel wells. It also pushed the differential pinion up (towards the floorpan). It's a BMR adj. TQ arm.

Then putting the Watts propeller in and lowering it again the rear end cover hung up on the propeller. It wasn't just close, I needed at least an inch more. I even tried flipping the propeller bolt for more clearance, too.

I bought this car used and I wouldn't rule out that the previous owner did something stupid... but I think it's all stock hardware. I must have things adjusted funky somehow. There's no guide on how to adjust the upper rod end in the torque arm to get the geometry correct... only the lower to adjust pinion angle. I wish BMR had put more literature in on how the upper rod end affects the install / geometric setup.

pewter2002

iTrader: (4)

Interesting. I have no experience with the installing torque arms, but i, like you, installed my Watts with extreme care.

I have not even half a centimeter of clearance, but the cover is VERY thick, as yours is I'm sure.

The Watts frame installs with no play or adjustment so perhaps the LCA's or torque arm are giving you the issue. I guess you have the rear axle supported as you proceed with the install? I'm going to get under my car and have a look tomorrow, it has been a few years since the install.

You could.always call Jim Fays, he is a real genuine car guy and will give you time on the phone. Can't say enough good stuff about him with follow up questions regarding his product!

Sam Strano

iTrader: (41)

I think your cover is just too thick. The Fays2 fits a lot of cars but when you get into bigger rear axles and all the various diff covers, there just might not be enough room.

transwiz

iTrader: (26)

I was thinking the same thing as Sam. That't why I never installed an aftermarket differential cover after my watts link install.I figured I would have clearence problems.

szalkerous

iTrader: (1)

I'm surprised with how busy you are these days you chimed in on my thread. Very cool.

I totally would agree if the wheels weren't inches too far rearward when put on ramps. I feel if they were centered in the wells front-to-rear there would be no clearance issues.

So I'd like to get this to happen with the pinion at the correct angle, and then see if I need to swap the cover off. It's on a stock 10-bolt, and the reason I went with it is for the internal bracing and drain plug. I want to squeeze all the life I can out of the factory rear-end before swapping up to something better... so bracing + easy rear fluid swaps...

I'm just not as versed with the tolerances of adjustment on the rear end as I'd like to be... and I don't have any decent shops around who are (to the best of my knowledge).

I'm going to take another crack at it on the weekend if weather permits, and I'll take some photos of the situation for a better visual feel. I have a theory I may have tightened the front contact point of the Tq-arm too soon, and it didn't seat forwards enough in the poly bushing. I should probably get a trans. crossmember relocation bar instead. Pain in the *** to bolt it to the transmission, and it's already cracked the tail seal once on me...

szalkerous

iTrader: (1)

Jim is a really nice guy. I owe him and Mr. Strano a lot of gratitude for the advice over the years... along with good products.

I just don't think this is an issue with the Watt's. I think it's an issue with my LCA/Tq. Arm install and setup.

I was tempted to call BMR/UMI about the adjustment issues but I was afraid they'd point at each other since the torque arm is a BMR, and the LCA's came from UMI.

Sam Strano

iTrader: (41)

I try.

I'm not sure why the Torque Arm would have shoved the axle rearward in the car. What kind/model TA do you have? If that's the case shortening the LCA's won't help because they aren't what is causing the axle to sit too far rearward.

99Bluz28

iTrader: (35)

IMO, if you have bolt-on LCA relocation brackets see if removing them allows the rear to sit further forward.

szalkerous

iTrader: (1)

The Torque Arm is a BMR TA001 Adjustable Torque Arm ( http://www.bmrsuspension.com/?page=p...&productid=315 )

The Lower Control Arms are UMI 2016 single adjustable ( http://umiperformance.com/catalog/in...roducts_id=105 )

The rear diff cover is an LPW aluminum cover for a FACTORY 10-bolt. (without the reinforcement hardware) ( http://www.lpwracing.com/Diff_Cover_...omparison.html )

I'm also using the FAYS2 Watts Link package, The rear adjustable sway bar from Stranoparts, and Stranoparts lowering springs / Koni shocks.

We've had strange weather up here in New England, but this weekend I should be able to get around to taking some photos.

szalkerous

iTrader: (1)

I haven't done any bolt-on or welded LCA relocation brackets. I was going to check the LCA's pitch after it was all dialed in to see if this was necessary with the Strano springs.

99Bluz28

iTrader: (35)

If you still have the stock TA, then remove the BMR and compare it the 2 and if it's still not some how possible to adjust the BMR to stock TA length, then reinstall the factory arm .

02Z28LS1

iTrader: (2)

these statements lead me to believe the torque arm is not adjusted correctly. i had the same problem, the wheels were farther back in the wells and the spring seats were rotated a bit upward, rotating toward the rear of the car.

i adjusted the torque arm and evened it all out, and now the wheels are centered in the wells again and the spring perches are pretty close to level with the ground again, the way they should be.

szalkerous

iTrader: (1)

Not to be a pest, but exactly which parts of the tq. arm did you adjust, and how much?

szalkerous

iTrader: (1)

So I wanted to come back and follow up. The past weekend I got under the car with some volunteer help and the shortened lower control arms in the rear were exactly what I needed.

After bolting it all back up, putting the wheels back on and setting the rear end under load (on ramps) I was able to adjust all the geometry and it now sits perfect. The wheels are perfectly centered front-to-rear in the wheel wells, the rear end cover has about 1" of clearance from the watt's propeller bolt, and the pinion angle measures in at about -1 to -2 (I'm using a Jegs angle finder... piece of crap!)

Anyways, it's all perfect as far as I can tell. I did have to fabricate new swaybar spacers for my Stranoparts adjustable sway bar because the spacers that came with the Fays2 weren't the right size... so I milled new ones out of steel stock. I also need to readjust the sway bar end links because I think the bar is supposed to sit parallel to the floor pan and it's sitting pitched up 20 degrees or so.

Other than that, very happy with how it all came together. Hopefully the KOOKS true duals will clear the Fays2 bar in the rear, if not gotta do some more fab.

Now to tackle my destroyed front suspension stock components....

libertyforall1776

iTrader: (2)

After reading this I am now wondering if the Trick Flow differential cover will clearance the Fays2 Watts Link? The cover seemed like a worthwhile investment to add stud girdles and cooling vanes for the 10 bolt.

http://www.trickflow.com/partdetail....0&autoview=sku

demonspeed

iTrader: (7)

LPW makes a low-profile diff cover:

http://www.lpwracing.com/Diff_Cover_...omparison.html

libertyforall1776

iTrader: (2)

Thanks, but I would prefer the Trick Flow unit since it also has some cooling vanes. I guess we could use a guide to know how much horizontal length a diff cover can be to still work with the Watts Link. I left a vmail for Jim Fay, I'll post the answer. Also requested the measurements from Trick Flow, waiting on their email reply, engineer is gone for the day.

BMR Tech2

iTrader: (5)

What I see as an issue here that can be causing all of this is how you are measuring your "pinion angle". Are you saying you adjusted your torque arm to make the pinion flange literally read -2*? If so that is not correct.

However your car is currently sitting, you need to measure the driveline angle. The best place to do this is to measure from the crank pulley. Then, you set your pinion angle to be 2 degrees less than what that measurement is. What the actual number is (0, 7, 43 etc) is irrelevant. All you need to be looking for is the difference in the 2 numbers.
I believe what you have done is adjusted the lower leg of the torque arm in so far to get the pinion angle down, that you have now placed everything in a bind and have the axle actually sitting at too much of a downward angle. Try correcting the angle as I have instructed and see if that helps your issue.