I have the CHE Adj panhard bar, and I've done the tape/thread/weight on each rear quarterpanel/fender to measure the distance from the thread to the wheel's center, and centered accordingly.

However, I can't but help thinking that there has to be a couple of reference points on the frame from which to determine if the dirveshaft is truly square (90ยบ) to the axle, so as to not add to the true operating angle of the DS U-joints.

Any ideas/experience?

 

The tape things is going to get you centered in the rear end but is not going to give you a 90 degree measurement in relation to the rest of the car. The only way to do that would be to jack the car up...level it. then take a plumb bob and measure off the rear axles on both sides. and put a mark on the floor. then use a frame bolt or hole (in this example lets say you use the K-member bolts (rears) hang the plumb mark the floor then measure left front to right rear, and right front to left rear. If they are the same it will tell you the rear end is centered reletive to the car's frame... you would then have to do the same for the tramsmission using say the front of the bell housing on each side then use a frame location in the rear.. measure the same left to right and right to left. that would tell you if the tramsmission in centered or 90deg reletive to the car. if it is then you would have to assume the driveshaft is 90.

 

I would have to think that the axle housing to drive shaft squareness would be built into the axle location controled by the LCA's. The adjustable panhard bar only controls the rear axle & DS location to the center of the body. The LCA's are attached to the body in the front and to the axle at the rear, if either of those mounting locations changed a great amount (as in collision) then the DS might not be square to the axle. If you have adjustable LCA's it would be freasible to get the axle out of square by having one LCA way longer than the other. Otherwise, I wouldn't think there would be much of a problem with DS to axle squareness.

My .02 worth.

Bobby M.

 

You bring up an interesting topic...i installed Steeda Ultralites a few weeks ago...putting in Tokico D-Spec's next weekend as well as new LCAs and an adjustable panhard bar. I will definitely take it to get aligned after i'm done but i doubt they'll make the panhard adjustments so i think i may have to do it myself. Any suggestions on how to make these adjustments myself to the panhard bar? Any illustrations anywhere that show how it can be done at home?

 

A quick search will give you all the info you need, but the short of it is to drop a weighted line down from the high point of your fender (taped to the outside), and measure to the edge of the tire or wheel. Measure both sides, and just twist the adjuster on the panhard rod until they're even. Do this with 1/2 tank of fuel, and if you want, ballast the drivers seat with your weight for the most accurate setting.

 

I'm about to get my pinion angle adjusted again along with everything in the rear centered etc. I honestly think that this is something I'm going to have to study and go over to do myself instead of letting a shop handle it...

 

Of those of you that have a strong intrest in chassis setup I recommend reading Door Slammers. it worth the 30.00.

http://www.amazon.com/Door-Slammers-.../dp/0963121707

 

Thanks, this is exactly the procedure I was looking for...I can jack the car up on ramps on all 4 corners and do this.

I did this already and have the axle centered between the rear fenders, so the tires stick out exactly the same distance on either side, but I'm not convinced that the fenders are equidistant to the center on the tranny

Thanks!

 

And therein lies the rub... If you want to insure that your drivetrain is installed parallel to your thrust angle, then more plumb-bob marks on the floor will do it... Drop a plumb across the center of the harmonic balancer, and also across the center of the trans output flange, and connect the dots, extending the line rearward. If that line also intersects the centerline of the pinion flange, then your driveline is in perfect alignment, at least in terms of the X-axis.

Now, compare the drivetrain axis to the track-width measurements of the car, and at any given point from front to rear, the distance from L to C and from R to C should be identical. Assuming that the thrust angle is also 0.1* or less, then your chassis and drivtrain is perfectly squared. Easiest way to measure trackwidth is to support the car on jackstands, loading the suspension, and drop a plumb-bob from the center of the axle flange in back, and the hub flange in front. These points are then connected, and provide a track-width measurement at any given point along the length of the car.

One simple factor can throw the whole kit and kaboodle off, though, and that is the amount of weight over the rear of the car. If you do all your measurements with no fuel and no driver ballast, then climb in and top off the tank, you will have induced an angle into the driveline as your rear axle will now be slightly offset. This is a function of the panhard rod design, which is why I always recommend driver ballasting and 1/2 tank of fuel when doing any suspension work, as that will average out the errors.

For what it's worth, when I installed my suspension kit, I used four different measurements to get set up prior to heading to the alignment rack.

1. Set front camber. With the suspension loaded on jackstands, measured "flat" above the floor, place an angle gauge across the hub flange, perpendicular to the floor, and adjust for desired spec.

2. Set front toe. With the tires back on, and the car on the ground (pulled out and back in again to settle the suspension after lifting, drop a plumb from the tire outer tread block edge to the ground on both the front and rear of the tire. Measure the differential, convert to an angle, and adjust to stock, WHILE LOCKING THE STEERING WHEEL CENTERED! Split your adjustments across both sides. Alternative method: Use a straight-edged piece of stock (2x2 box tubing or the like) pushed up against the edge of the tire to create a line. The rest is the same. I prefer the plumb-bob myself.

3. Set pinion angle. This has been discussed and well explained. Take your measurements from the pinion flange, not the housing. They are NOT perpendicular! The pinion angle was set using the UCA.

4. Square rear axle. I took wheel centerline measurements (fender plumb-bob across the center of the center cap to the floor) to adjust the LCAs to equalize the wheelbase on both sides, after roughly centering the rear springs in their mounts.

5. Center rear axle. This is the panhard rod adjustment that I described earlier. I used the fenders as reference points, and measured distance to a machined surface of the wheel with the plumb centered on the center cap.

Bearing in mind that the suspension kit I installed was relatively large (adjustable UCA, adjustable LCAs, LCA relocation brackets, struts, springs, swaybars, and bump-steer tie rod ends, along with some chassis bracing), and the method I used was to gut then rebuild, rather than replacing parts one at a time, using the alignment methodology above, I wound up on the alignment rack with less than 1/16" total toe error. Camber was dead even, the thrust angle was bang on, and the pinion angle was perfect.

The kind of measurements you're looking at taking and worrying about are, IMO verging on excessive. Assuming that your car has never been wrecked (all bets are off if it has), then there isn't a lot to adjust to change things. Yes, there is some slop in the K-member and trans crossmember positioning, so you could pick up some error there, but in reality, it's just not going to be that far off. Centering the driveline when welding a motor plate into a tube chassis? Sure. OTOH, that level of detail, while perhaps delivering diminishing returns, certainly won't hurt.

If, though, you're trying to isolate a drivetrain vibration or the like, it would take a LOT of error in offsetting the axle pinon in relation to the trans to induce a noticeable vibration. My guess there would be upwards of two or three degrees, which is pretty huge.

 

WOW! Your attention to detail is very much appreciated. Yes, I'm trying to isolate a hum/murmur at 110 on decel, that appeared after installation for the Spydershaft/CHE UCA and CHE Pahnhard bar. The pinion angle is bang on per the Spicer/Dana manual (tranny and pinion are parallel), and the hum did subside and the threshold at which it occured got raised when I rotated the DS 180ยบ, but it's still there. Ron (Spyder seems to have gotten rid of his hum by swapping out the Tracloc LSD (multi-clutch)to a Truetrac LSD (twin helical gears)....but I want to eliminatye all other possibilities before I drop $580 for a Torsen T-2 (also twin helical gears), because I'll probably also do the 4.10's, by which time I'm looking at $1200 with labor.....
Thanks!

 

Marc, I completely understand trying to minimize expenditures when possible! I would ask you to remember, though, that one of the main reasons that Ford put the 2-pc shaft into production was to help reduce drivetrain NVH transmission to the chassis... The slop acts as a silencer, as does the softer suspension bushings. Now that you've changed a bunch of rubber out for poly (or rod-ends), and added an undamped resonant tube to the drivetrain, I think that some NVH increase is to be expected. Is it just noise, or is there a tactile vibration involved?

 

Dave,

Thanks for your continued interest in this matter.

It feels like one of the rear tires is out of balance...you know, no shimmy in the steering wheel, but the seat-of-your-pants hum when it's one of the rears that's out. The thing is, I just had Discount balance them to the nearest 1/10 Oz (usually they do it to the nearest 1/4 Oz), which involved rotating a tire on the rim, so I don't think it's the tires....but that's something else I could do...since I have no shimmy at any speed in the front, I could rotate to ensure it's not the tires/wheels that are causing it. The other thing that leads me to believe it's not the tires, is that the intensity of the hum/murmur did get reduced somewhat and the threshold where it happens raised when I rotated the shaft 180ยบ....

Based on the procedure you provided above, I had an idea: I'm going to hang a plumb from the middle of the harmonic balancer, one from the tranny output shaft flange, and one from the pinion flange, and then I'm going to use my wife's Laser Trac, line the laser beam up with the front two, and correct the rear end until it's inline with the other two (when the line from the rear end plumb is being hit by the laser).....waddayathink?

 

I wound up having my tires balanced THREE times by two different Discount Tire shops before my shimmy stopped... I feel your pain there...

As for squaring the drivetrain, personally, I would center the rear-end in the chassis, referencing the fender lips first, and then double-checking against the front LCA mounts. You have fixed LCAs, no? I would also double-check the wheelbase. If you have more than 1/8" or so of wheelbase variation, then I would consider going to adjustable LCAs. Once you have the axle squared to the chassis, with the pinion angle set, I would take a visual peek at the rear spring "tunnels" to ensure that the springs are still roughly centered. If the PI adjustment was extreme, you could rotate the axle housing enough to get the springs rubbing against the rear (or front) of the spring well.

Assuming all is good there, THEN I would hang the plumbs from the balancer and trans output flange. Take some more measurements (say from the rear K-memeber bolts to the balancer) to verify that the motor is reasonably centered, and do the same with the trans flange. IF you have a mis-alignment, I would start by loosening (slightly) the trans crossmember to chassis bolts, and gently pry the entire trans until the engine/trans combo lines up with the axle. I'm not sure where there is any mounting slop on the engine itself, but I would bet it would be on the motormount plates that bolt to the engine. That would be the next adjustment point.

Essentially, your goal is to get the entire driveline square to the chassis, and you have to start somewhere. The axle is the easiest with the adjustable panhard rod, plus it's the ony part of the driveline that really moves around at all. If it's off-center, then you're reducing the range of motion in some axis, which is bad. Once the axle is squared up, then you square the rest of the drivetrain to it, and you're done.

 

The amount the drive shaft angle might be off of 90 degrees to the axle is hardly of any consequense unless the frame has been wrapped around a pole. Whats more important is the alignment of the rear axle relative to the front suspension. To check that you need to go to a good alignment shop to get it measured up. If it is off relative to the front suspension there is really not much you can do unless you have adjustable LCA's.

 

It also changes the natural frequency of the drive shaft which moves the critical frequency for drive shaft vibration further away from normal RPM range.

 

Thanks for your input, RadBOSS. My wife bought be 10 smallish plumbs (actually 3" eye-bolts) that I'm going to hang from the:

• front suspension control arms,
• harmonic balancer,
• tranny output flange,
• pinion flange, and;
• the points where the rear LCA's attach to the rear axle.

Then, I'm going to measure from the font CA's to the HB and TF, to check that the engine/tranny are centered, and then shoot the laser from the HB plmb, through the TF plumb, to align the pinion with them for a 0ยบ (top view) thrust angle.

Then, I'm going to measure from the front CA's and TF to the rear LCA's to see if the rear axle is square to the front suspension and to the DS. I guess adjustable LCA's might be in order....if the rear axle isn't square to the DS....

And if I still have the hum/murmur at 110, I'm ripping out the TracLoc LSD and installing a Torsen T-2 with 4.10's....

 

Have you ever measured the circumference of the left and right rear tires?

You may have to sacrifice perfect engine trans alignment to the rear axle infavor of optimizing the alignment of the rear axle to the emgine / trans, which I think is more important.

 

not sure I follow you... There IS slop in the engine and trans mounting, which means that it is possible to have them non-paralell with respect to the chassis centerline. Optimizing that is a solid first step, and while certainly not the most likely source of Marc's decel whine, postively won't hurt anything. If he gets his chassis and drivetrain completely squared, and still has noise issues, then at least he's eliminated a variable.

Also, unless I'm mistaken, a tire circumference differential large enough to impact the rear end would have impact on both accel and decel, and would most likely cause a pull under all circumstances...

 

Ok, in order to be able to align the harmonic balancer, tranny output flange and pinion flange, the driver's wheel now sticks out 12/32 (3/8") more than the passenger side. This was done by centering a plumb on the HB, TOF and PF. To hang the plumbs from the TOF and PF, I got under the car while the tires were still suspended in the air, with the tranny in neutral, rotated the DS until one of the unused holes of both the TOF and PF were at their lowest point, and then used a level to make sure it was the lowest point (by resting the level against the opposing ends of the u-joints. I then tied the plumb line through the holes.

Aligning them using the laser turned out to be tedious and not as accurate as I'd liked, so what I ended up doing is setting a dark object in front of the car (the plumb lines where white), and lying down behind the car, alinging the HB and TOF lines with my eyes, and then looking to see if the PF was in alignment also, which is wasn't: so get under the car, rotated panhard bar, check again, and so forth, until it was all in alignment, then, while lying down behind the car, I moved from side to side verifying that when the HB to TOF lines were at X distance, and the TOF and PF lines were at Y distance, they looked the same from both sides...this required a bit more fine adjustment on the panhard bar.

I also hung plumbs from the rear bolt on the front LCA's, and from the rear bolt on the rear LCA's, and measured....and regardless of adjustment on the panhard rod, the distances had minor discrepancies:
HB to FRLCA 530 mm
HB to FLLCA 526 mm
TOF to FRLCA 1052 mm
TOF to FLLCA 1056 mm
RFLCA to RRLCA 2602 mm
LFLCA to LRLCA 2606 mm
HB to RRLCA 3012 mm
HB to LRLCA 3009 mm
TOF to RRLCA 1702 mm
TOF to LRLCA 1700 mm

etc etc.....my conclusion on the LCA bolt locations, front and back, is that they have manufacturing variations, which is why the front end needs to be alignable.

Consequently, as a reference I find the bolded measurements (harmonic balancer and tranny ouput flange to rear LCA bolts) are the ones that correlate with what I had to do to align the thrust angles....i.e. the engine and tranny sit slightly left-of-center in my car, and therefore I had to move the axle towards the drivers side to align all 3 points. At some point I may move the engine/tranny 12/32" towards the passenger side...if that's possible...

I have pics, but TMS only sporadically allows me to post them, for some reason. Dave: could you email me at S197.mustang@hotmail.com so that I can respond with the pics and maybe you can post them in a subsequent post?

 

BTW, tested this morning up to ~125 mph (on a closed track, of course ), and the hum/murmur is almost gone and happens at a higher speed...on decel I think it stopped at ~115 mph, and I had to put it in neutral to hear/feel it....even in 5th at more relaxed engine speeds it wasn't perceptible while in gear.....

Sooo, what do y'all think? Live with the fact that I still have a slight hum at higher speeds (120+ mph), or reinstall the OEM noodle DS?

BTW, I think this misalignmet of the driveline (I'm all Mustangs are a little different, depending on where the welds were made on the frame, how the engine/tranny was bolted in, etc, etc..) is another reason for Ford having developed the noodle DS with a vib damper...