There are some unusual wear patterns on the u-joint in a 1940 ford car. The car has a 350 with a 400 turbo in it there are also some vibration problems. The vibration problem is only during coasting while the car is in gear and not while the car is in neutral and coasting but in gear and coasting. I am nearly positive that the vibration is not there while accelerating but I am not 100% positive about that. The rearend in the car is a 8" ford from a 70's era granada. I am not sure if the vibration is the result of the u-joint wearing or caused by another underlying problem the angle of the rear axel is 2 degrees pointed down this is all of the information I can think of to provide to help solve this. Here are some pictures of the offending u-joint I marked with a red marker all of the wearing patterns on this spicer u-joint. To explain a little about what you are seeing of the many angles the easiest way to understand what you are seeing is the galling (gouging) is on the axel side of the u-joint the other side has some shiny spots on it and the shiny spots are on the driveline side of the u-joint. the wear patterns are 90 degrees apart from one another so that means the wear on the driveline side is not facing you when you hold the u-joint in your hand but the wear on the axel side is facing you when you are holding it in your hand and looking at it. There is some wearing on the very ends of the u-joint too but I think this is probably normal. The u-joint that was removed last year had wear patterns exactly like this but I did not think much of it at the time.
It may be that your car just don't have angularity for the U-joint to work as it is should. U-joints with less than ideal working angularity often exhibit the wear you have there. The bearings just aren't getting worked through the cycle as they need to be for long service life.
Rear axle pinion should be pointing up, not down. The angle should be the same as the transmission angle, but in the opposite direction. Most transmissions are 3 degrees downward, and pinions 3 degrees upward. The two angles cancel each other out.
You told us the rear end is 2° down, but not what the trans output shaft is. Without that the rear is meaningless
hotroddon-I have looked at the output of the transmission but I do not remember what that angle is. Mike51Merc- According to some of the engineering books I have looked at you always want the rear axel pointing downward because you have deflection under load that will "wrap" the axel upward. That is why slapper bars work because the slapper bars will stop or slow the wrapping of the upward movement of the axel when under load. pasadenahotrod- Thanks for that I will look into it. Although I had been informed that I may be torquing the u-joint down too much on the axel side.
Did you replace both U joints at the same time,,and forgive me my eyes are not the best but the universal sure looks dry,,did you grease it when installed? HRP
Hotrodprimer- Yes it was greased well I just had cleaned it up well and have had it taking it around to some people asking them if they have seen anything like this before that has been about a week now. Last year I replaced both u-joints but this year I only replaced the axel side because it was bad the slip yoke side of the driveshaft is still good.
I think you better read this http://www.iedls.com/asp/admin/getFile.asp?RID=10&TID=28&FN=PDF Your Engineering books are somewhat correct for a Drag Only car, but for a street car please pay attention to the link I posted.
Take a look at this thread.It should answer your questions. http://www.jalopyjournal.com/forum/showthread.php?t=826855&showall=1
If I'm not mistaken shouldn't the transmission and yoke on the rear axle be parallel with each other? HRP
Buy better joints. Some of that can come from a car that idles too fast, ie. big cam. You put the car in gear, then there is lash in the rear, The bang when everything catches up causes this. Better joints have harder crosses, takes more time to show up.
My first though was it looks like the cap U-Bolts were torqued down too much, not allowing it to spin. That doesn't explain all 4 sides being burnelled though. Im with the crowd, check the driveshaft angle.
Check the down angle of your trans output shaft. Set the rear pinion angle up (not down) so that it is within 1 degree parallel to the trans output. So if you have the trans at 3 degrees down, set the rear for 2 or 3 degrees up. This is the rule I have followed and have never had an issue. From what I know, on a street driven car (unless you are under conditions of constant acceleration, which is not likely) you shouldn't worry about compensating for axle wrap.
I dont know what the actual torque I put on them was but I took a wrench and tightened the nuts up then I stuck another wrench on that and torqued them down at the advice of the gut that built the driveshaft. The u-joint has gouges on the driveshaft side where the u-joint was tightened and the small roller bearings gouged into the actual metal. The wear on the driveshaft side is not bad but just shiny spots. I dont want anyone to think that all 4 sides of the u-joint are gouged deep take a close look at the pictures and you can see what I am talking about.
I just looked it up in a Mopar factory service manual, the torque on the axle strap screws is 170 inch pounds for a 1/4" diameter bolt, 300 inch pounds for a 5/16 diameter bolt (about the amount of torque you can put on with a 4" long wrench!) How long is the wrench your doubling up on? When you replace this u-joint, replace the straps and bolts as well, yours are probably about ready to break. Gene
Even on a street car i run pinion down to drive shaft. With leaf springs i rin 3.5 to 4"° pinion angle down. Been doin this for 27 years on every car i have set up with leaf springs, not enuff angle in the drive shaft and it whips around under coasting. Look under any car or truck & u will never find a straight line on the drive shaft. Case on point look under any truck that runs a split shaft with a carrier bearing. I would bet u run 3.5° down pinion amgle͵ torque the ujoint bolts "& use a good quality ujoint your problems will go away. I dont get the idea of running a pinion up. I guess they cant figure out a pinion climbs during acceleration even in a street car. so run 3 ° up and under exceleration your looking at up to 7° of angle and then u will start wearing out ujoints drive shaft vibration and tire shake. Even on the street.27 years & i will still run the pinion lower than the drive shaft.
i believe your vibration and u joint troubles might be two separate issues. 1. the u joint wear is brinelling caused by a lack of a u joint working angle, make sure the u joint and drive shaft are NOT parallel. a working angle of .5 of a degree is an absolute minimum. 2. the vibration on coast could very well be a loose pinion nut or a lack of preload in the pinion bearings. changed the yoke or seal lately?
Torque deflection under load (spring wrap) is a temporary condition, not the norm of typical cruising. I'd rather the angles be "wrong" under hard acceleration and "right" under highway cruising.
that's exactly why drag cars are set up different than street cars. As you state above for street cars For drag car you want the angles "right" for hard acceleration factoring in the pinion climbing.
A drive shaft is not made to be used in a straight line, vibration,whip.abnormal wear are the effects of doing so. The pinion angle does 2 things. It prevents the above problems & it provides a happy median between full load & neutral position. But leaf springs move even under light loads. Ford "& mopar both hav put pinion snubbers under many of their cars and trucks for years, why ? Because the pinion naturaly wants to climb. Not just under acceleration but also load. Not only do leaf springs wrap but u also hav suspension travel. Under normal driving most movement of the body is downward thus the suspension is moving up thus thru this travel the pinion angle is lessened. Put a couple friends on the back seat, more weight so less pinion angle. More weight more load so springs want to wrap under even minor aceleration so less pinion angle. Just about all movement negates pinion angle. Another interesting point most driveshafts are also offset side ways in a car thus the offset of the pinion on a 9" ford rear, mopar did it by offsetting the engine. Amazing the amount of trial and error has been done just for a drive shaft.
There is no way that your rearend should be pointed down ... your setup is out of phase. With your car's suspension loaded the imaginary line of your crankshaft/output shaft (they are a straight line) and differential shaft should be parallel. You can put your inclinemeter on your oilpan to block mating surface to get your forward angle.
This Up, down bullshit drive me fucking crazy! Makes me want to set myself on fire ( thats pretty crazy huh?) Notice in the top sketch the lines are parallel. Parallel means both are going the same direction - exact same direction. Since we all like to say "engine down" implying toward the rear then the pinion is also going down toward the rear. Notice in the lower sketch the lines intersect. Intersect means they are heading in different directions (not 180*) and will eventually cross if extended both ways. Once again: Since we all like to say "engine down" implying toward the rear then the pinion is going up toward the rear. And BTW either way will work correctly if the ujoint working angles are set equally.
The Jalopy Journal
