My apologize if this has been asked before, but I'm in need of a little help. I have a 1987 K5 Blazer with a 4" lift. About a year ago the ring gear blew apart and sent metal into everything. I have since rebuilt the whole new differential with an Eaton posi unit, along with a new axle housing that I got from a buddy. When the rear end was put back into the truck the pinion angle was way off. It rode fine just had a lot of vibration over 35 mph. I took it to a local shop and he recommended I get 4 degree shims to adjust the angle. So this weekend I installed them and the pinion points directly up at the transmission. To my knowledge this should only be like this if I have a CV drive-line correct? Truck drives fine still has vibration but I also have 35 mud terrains so i suspect that's the vibration I'm feeling. Problem now is I'm losing gear oil at the pinion seal. I'm stumped I even took an angle finder and at the base of the drive-line its 17 degrees, at the top its 16 degrees. I'm sorry if this is jumbled and doesn't make sense but, spent over a grand in parts and I'm not looking to screw something up. Any help would be greatly appreciated.
CK5
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Pinion Angle
- Thread starter Zach'sK5
- Start date
Assuming 17 degrees is the driveshaft angle, you'll have vibrations unless you have a CV driveshaft.
The leak is a separate problem, can you move the yoke in/out or side/side at all?
The leak is a separate problem, can you move the yoke in/out or side/side at all?
Did you have the vibration before the gears went out? If the axle wasn't shimmed before the only difference would be the gear set up unless I am misunderstanding. Also with the leak at the pinion I would wonder about the pinion bearing.
Assuming a couple of items here so OP fill in the blanks if I'm wrong. You have a 208 T-case with a slip yoke right? 4" lift by blocks or springs or shackle flip? 10 Bolt diff?
Did the vibration start shortly after the lift before the first diff grenaded? Is the vibration happening under accel or decel, both or one or the other?
The description sounds like a driveshaft angle problem. The combo of 4" of lift (regardless of how it got lifted) and a slip yoke style t-case are usually the reason for a driveline vibration. The shaft itself is short to start with. Then you go and drop the rear axle down to gain lift, the shaft has to run at a steeper angle to "connect the dots" from one yoke to the other. Yes, pinion angle shims can correct for a minor problem, but in a two joint shaft system you need to have each joint angle within 2 degrees of each other to keep the joints happy. You can't just look at what the angle of the shaft is, you need the pinion angle and the angle at the t-case. If you are not at the 2 degrees or less, equal and opposing you'll have a vibration.
That vibration is enough if you keep driving it to wipe out the pinion bearings/seal in the diff as well as the output bushing in the t-case. I'm not surprised if you have a pinion seal leak now if you have been driving it. I'd be looking at either end for visible slop when you put your hands on it.
One other thing, a shop put in a 4 degree shim? What brought them to that conclusion? As you said if the driveshaft angle matches the pinion angle that's ideal for a shaft with a CV joint on the front side. Why would they set it that way with a non-cv shaft?
You need to take accurate measurements. Also don't overlook the length of the driveshaft. Where is the slip yoke sitting at static ride height? If the shaft is too short it could fall out when the suspension droops, too long and it may bottom out during suspension compression.
I'm thinking you probabaly need a c/v shaft and maybe another pinion angle adjustment to nail it down.
Did the vibration start shortly after the lift before the first diff grenaded? Is the vibration happening under accel or decel, both or one or the other?
The description sounds like a driveshaft angle problem. The combo of 4" of lift (regardless of how it got lifted) and a slip yoke style t-case are usually the reason for a driveline vibration. The shaft itself is short to start with. Then you go and drop the rear axle down to gain lift, the shaft has to run at a steeper angle to "connect the dots" from one yoke to the other. Yes, pinion angle shims can correct for a minor problem, but in a two joint shaft system you need to have each joint angle within 2 degrees of each other to keep the joints happy. You can't just look at what the angle of the shaft is, you need the pinion angle and the angle at the t-case. If you are not at the 2 degrees or less, equal and opposing you'll have a vibration.
That vibration is enough if you keep driving it to wipe out the pinion bearings/seal in the diff as well as the output bushing in the t-case. I'm not surprised if you have a pinion seal leak now if you have been driving it. I'd be looking at either end for visible slop when you put your hands on it.
One other thing, a shop put in a 4 degree shim? What brought them to that conclusion? As you said if the driveshaft angle matches the pinion angle that's ideal for a shaft with a CV joint on the front side. Why would they set it that way with a non-cv shaft?
You need to take accurate measurements. Also don't overlook the length of the driveshaft. Where is the slip yoke sitting at static ride height? If the shaft is too short it could fall out when the suspension droops, too long and it may bottom out during suspension compression.
I'm thinking you probabaly need a c/v shaft and maybe another pinion angle adjustment to nail it down.
