Drive Line Angles

hi it's scott webster with toyota technical training and i wanted to do a quick little uh clarification i guess on how to measure driveline angles we've seen some issues with improper measurements here a couple of things about driveline angles one you may notice the way we have the truck sitting here we're on an alignment rack uh we don't have the rear suspension either drooped or compressed we're trying to duplicate the actual ride height that the vehicle would be under in a normal situation that's going to affect our driveline angle so we've got to make sure that we've got this thing at normal ride height we also have the wheels up in the air so that i can spin the drive shaft so i can make these these measurements now one of the scenarios we may be in here is we've got a vehicle that has a what we suspected as a driveline angle vibration it vibrates at highway speeds uh calm common diagnostic remove the rear drive shaft put the transfer case in four wheel drive drive it on the front axle only vibration goes away i know it's something in my rear drive shaft so then i would have to make these types of measurements when we're talking about a driveline angle you can see i've got my nice magnetic angle cube here on the drive shaft this is not what we're talking about this is part of the measurement but that angle is strictly just the angle of the drive shift what makes a drive shaft vibrate is when there is a difference in the angle of this joint versus one or two of the other joints so we need to know the actual angle of this joint not just of the drive shift so it's going to involve measurements and it's going to involve a little bit of math nothing horrible so if we look at the joint you can see that i've got the flange for the transmission on the back here and this part of the joint is actually bolted to the flange this part of the joint is part of the drive shaft so we need to know the difference in angle between the flange and the drive shift so a convenient way to do this on toyotas at least we machine the yoke to match the u-joint so i can take my angle cube and i can put it right on that machine surface nice and flat make sure it fits make sure i'm straight and i'm always going to make my angle measurements from the same side so i'm going to get my head in the way here so that is a 2.4 degree angle so that is the down angle of the back of the transmission output shaft now i need to jot that down 2.4 then i'm going to rotate the shaft i could just take my drive shaft measurement like that or i can use the machine surface make sure i'm straight i had 2.4 and now i have 5.6 so 5.6 minus 2.4 that's 3.2 degrees so there is a 3.2 degree angle that this u-joint is running at we don't ever want that to be more than five we want it less than five but that's not the only thing that's going to make it vibrate this angle has to cancel with the other angles i'm going to make this measurement then i'm going to move and i'm going to make this measurement right this should be the same get my roughly 5.6 degree so that's this then i'm gonna go and rotate the shaft and i need to measure the angle of this shaft which is 5.1 so if i had 5.6 5.1 i've got a half a degree angle on this joint so we had a three some degree angle here i had a half a degree angle here they're both heading down i'm going to add those two together okay now every time these u-joints spin they create a little bit of vibration because of the design of them so as long as these two angles cancel with that one we're going to end up with a drive shaft that doesn't vibrate so if i go all the way back here i'm going to get my final measurement and i'm at 5.1 that's good because that's what i had up there and then i rotate and i'm going to measure the pinion flange at 2.1 5.1 minus 2.1 is 3 degrees now this is 3 degrees going up so i got a 3 degree angle down here i got a half a degree and i got a 3.2 i believe it was up there so if i add 3.2 and a half that's 3.7 this is 3 my 3.7 minus my 3 i have a 0.7 degree difference between all the drive shaft angles we want it to be about a half a degree um 0.7 i'm not going to argue with that that's going to make this thing not vibrate because the vibrations created by the front part of the drive shaft is going to cancel out by the vibration created in the back of the drive shaft so as long as it's when a half three quarters of a degree we don't have a problem here with driveshaft vibration all right so we showed you some things about measuring the difference in these angles and getting our actual joint uh running angle let me show you a little flat rate trick our angle cubes that i've got sitting here on the lift you notice it reads zero i've pressed the zero button and zeroed that out to make sure that my cube is zeroed out but we can use that zero function to do a little flat rate trick here if i find my transmission output shaft angle here and while i've got that in the proper location if i zero it out right now all that cube's going to tell me is the difference between the two angles i don't have to do the math so right now it reads zero when i spin this around and find the drive shaft angle it reads 3.2 degrees that is just the difference between where i started and what i have now it's a much quicker way to get our angle okay so now we've measured our angles we're pretty sure we have an issue our angles aren't canceling what do we do to fix this all right now we have some tsb's that talk about uh leaf spring replacement so if you look back here uh the angle that this leaf spring has the rear diff mounted that's going to change this pinion height that's going to make the front of the diff either go up or down by replacing a leaf spring with maybe a wedge in it or some sort of caster wedge in there now the tsb has that built into the spring pack so that's why we're replacing spring pads aftermarket parts you can get a wedge that would actually change the angle of this diff we also may shim down this center bearing if you put some shims under here you could bring the center bearing up or down that was is going to change our angles and we have a tsp that talks about replacing the rear transmission mount obviously rear transmission mount that's going to change the height of the transmission that's going to affect this angle all right thanks

Channel: Toyota Technical

Views: 6,533

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Id: qVOzRvtn9wI

Length: 8min 5sec (485 seconds)

Published: Tue Apr 27 2021