I got to wondering if my pinion angle was wrong because of a shimmy that my 55 Fairlane has on the highway, probably around 65-75 MPH or so. I don't have a working speedo or tach, so I don't know for sure. I was pretty sure it was alignment related, so I'll hopefully get that looked at tomorrow. The car feels great on regular city streets. I thought I had it all set in my mind and everyhing looked good, but then I started reading up on a website that I found, and now I'm all confused. I used the angle finder that I bought, the one I have points straight up all the time. So, if the car is parked on a slight decline, it reads 2* on the valve cover. I held the other side up against the face where the seal goes on the third member and it seems to be between 0 and 2 depending on which side of the third member I'm on. But the website I was on makes it sound like you add the angles toghether to get the actual pinion angle, or something. It would seem that if they were both at 2* the driveshaft would be straight and the U joints would have minimal stress on them. But, if you DO add the numbers, if the car was level then both of the angles would be closer to 5 or 6, and then I'd have a 10* pinion angle? I guess I'm really lost on this. Am I using the wrong kind of angle finder? Or does it seem to be all set.
I should mention that the driveshaft and U joints are all new, which is why I'm curious. We used a different tranny than the stock one, and I had to make a little mount for the rear of the tranny. I used a bunch of little strips of rubber and 2 pads that I cut from a steel plate for the mount, but I'm worried that if I used too many or too few strips of rubber, or if the metal pads I cut and bolted to the cross member are too low or high, it would raise or lower the engine and tranny angle enough to throw off the pinion angle and break stuff. So, I want to measure to be sure.
my understanding is that when you replace BOTH u joints you need to rebalance the shaft?? Not certain about this of course but thats what I have heard..
Your Pinion and transmission should be parallel. Check to ensure you didn't crank the U-Joint straps down too tight, I recently tore up a joint that way. TZ
[ QUOTE ] So, if the car is parked on a slight decline, it reads 2* on the valve cover. I held the other side up against the face where the seal goes on the third member and it seems to be between 0 and 2 depending on which side of the third member I'm on. [/ QUOTE ] You need to measure at the tranny tailshaft, not the valve covers, for accurate angles. Other than that, you want them to be the same so the extended centerlines of the tranny output shaft & the pinion are parallel with each other. Make sense? (easier with pics, but I don't have any...)
[ QUOTE ] You need to measure at the tranny tailshaft, not the valve covers [/ QUOTE ] Acutally the vavle covers are going to be dead parallel to the crankshaft on the engine and thus dead parallel to the mainshaft/output shaft of the transmission. So this is a good place to measure engine angle. The same angle or less on the pinion shaft is just what you are looking for on a parallel leaf sprung rear axle where the transmission and pinion shaft are nearly the same height from grade. This situation sounds as if everything is in reasonable shape angle wise. Things to check, It wouldn't hurt to check the slip shaft bearing in the transmission. If it doesnt fit well it will cause the driveshaft to whip at higher speeds. Make sure the slip yoke is well inside the transmission, again if it is too short it will cause problems. Check out the rear end, if the gears are worn out you can have excess lash, but I think we already checked that out. Have the tires been balanced? Discount tire is cheap or free to rebalance them. Also check torque on all the wheel lugs.
Flat Ernie, I tried that yesterday, with the tranny tailshaft and, wouldn't you know it, there is a crossmember in the way of the angle finder. I'm getting the alignment today and if it still shakes, I'll head to Discount Tire and get them all balanced again. The aligmnent guy, said it would take about 45 mins and cost me about $43. God I love this old shit. El P, this is a different gear set, when we took that pinion nut off of the other chunk and counted it back on, it leaked like you've never seen anything leak before. Started with a slow drip and just pissed out after driving it for a while. I didn't feel like bothering you with it again, and Miles knew someone right around the corner from us that did a rear end for his Camaro. I also picked up a 2.90 gear set from NealinCA, so I brought him that one. Makes highway driving fun now. The old set was 3.89.
Did we ever check the axles and see if they were straight? How about the wheel bearings did we do those too? I can't remember. Oh yea, I forgot to tell you when you get the wheels balanced to ask the guys at discount to check for bent wheels or out of round tires. are you running bias plys or radials? I have had bias plys flatspot and cause all sorts of havoc from sitting in one place too long.
I got the alignment and the had the wheels re-balanced and rotated today. It seems a bit better. One of the wheels does have a very slight bend or highspot in it, but I've driven much worse than that. I've got radials on it now and they are a little over a year old. It feels pretty smooth (I think) on regular roads, it is just on the higway at about 50ish. If I swing it by sometime would you have a chance to give it a quickie look? The guy at the alignment place eyeballed it and said it didn't look like it was too crazy.
[ QUOTE ] Acutally the vavle covers are going to be dead parallel to the crankshaft on the engine and thus dead parallel to the mainshaft/output shaft of the transmission. So this is a good place to measure engine angle. [/ QUOTE ] Naturally, I don't know what engine/valve cover combo Deyo has, but I've seen plenty of valve covers that were not parallel to the crank. While most times it's close enough, I'll stick to my statement that the absolute best place to measure is the output shaft of the tranny. My opinion.
Just out of curiosity I would love to know which engines you have worked on where the vavle cover is going to be different from the crank, IE not parallel. Not taking into account lumpy valve covers and Cal Custom aftermarket, the mounting surface should be a close second on those applications. I have however seen a few old transmissions with messed up output shafts due to poor machinework or rough abuse over the years that would not allow accurate measuring. The outside of most standard transmissions do not have surfaces parallel to the output shaft either. Under a car in your driveway it is not all that easy to get an accurate reading. Yes I do have an unfair advantage by knowing the situation a little better than you. He has a stock 272 Y-block Ford with stock covers and a three speed trans. Given his situation and lack of experience I gave him some easy to follow instructions for my information purposes. As far as trying to get the angle down past degrees into minutes and seconds is usless with a parallel leaf sprung axle. Besides with an inexpensive angle finder you are going to have a degree or two of error. Again in this case a few degrees in either direction will not cause a major driveline vibration unless you are traveling at very high highway speeds. But that is a different situation all together.
I find that lower frequency vibrations are tires, driveshaft vibrations at freeway speeds are more like a buzzing sensation. Especially with todays shitty tire quality control.
It doesn't seem as bad since they balanced them, so maybe the problem is in that one "bent" rim. Before, if I was driving along at whatever speed range it is that it vibrates, if I said, "Ahhhhhhhhhhh" my voice would vibrate also. I've driven with a snapped belt in a tire once, and it isn't quite that bad either, and nowhere near as bad as when the old driveshaft/tranny shit out on me on the highway. That was the vibration of a lifetime.
a tire can also spin balance perfect but still not be a round tire causing the type of vibration/shimmy i think you are discussing. If you are feeling the shimmy in the steering wheel move the fronts to the rear and see if the vibration moves, this will help eliminate some other ideas. If you feel the vibration more in the seat of your pants/console etc. it might be a rear tire, moving them to the front may cause a shimmy in the wheel. be sure to mark each wheel so you know where they came from.
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