I was under my Blazer , and I happen to notice that my rear driv shaft seemed loose . I can wiggle it up and down at the rear . Upon closer inspection , it seems that the imput shaft to the rear diff has play in it . No oil coming out of the seal , just play in the shaft . It seems like that should be solid as a rock , with no play at all . Am I right ? Is the bearing that hold that shaft bad ?

If it is a bad bearing , Im assuming it is just on the other side of the oil seal . Can I relace the bearing without pulling the diff cover ?

 

Even worse you have to pull the cover, the carrier, and the axle shafts. Then the baring is pressed on. Maybe the bolt just came loose but doubt it

 

are you sure its not just a u joint? thats a whole lot easier to change

 

I attached a pic of which part has play in it . It moves up and down , meaning that it presses more against the oil seal on one side , and less on the other , and vise versa . Am I correct in assuming that there should be absolutely NO play in this way ? Is a little play OK on a high mileage rear end if there is no oil leaks ?? Should I change my rear diff fluid and what to see if it gets worse over time ? Its probably boned , because the truck makes a "light whirring" sound on accel or decel , and there is a shimmy/vibration at 70MPH+ , but these symptoms are faint , and might not be related to the rear end though .

If its a bad bearing , and needs to be fixed right away , I will just swap out the rear end . I could probably pick one up for $100 . The truck has 212,000 miles on it . I have no idea if the rear diff fluid has ever been changed , but I do know that the truck has never been taken out in the woods and thrashed .

Just to clerify , I attached a pic with an arrow pointing to the part that moves .

Here is the pic :

 

if its your pinion bearing it should howl when you drive and should clunk when you put in gear and also move in the third member.

sorry i didn't completely read the post,its your pinion bearing but they are not that hard to change.

 

Pinion bearing ? Ok , so should I stop driving the vehicle ? If its easy to change , what the procedure ? Pull the drive shaft , take the large nut off , take off the u-joint holder thing , pull the oil seal , pull the bearing , then do the reverse with new bearing and seal ?

Im just guessing here .....

Whats a pinion ?......

 

you have to pull the axle shafts out the sides of the axle too along with the carrier cause the bearing is on the inside of the axle. and the bearing needs to be pressed off. . ive never had to do a pinion bearing on anything ive owned but have seen it done. theres also a crush sleeve that goes in there that has to be torqued properly and the rear end needs to be put back together exactly how you took it apart. its kinda a big job for a shade tree mechanic.

heres what i found on google just to give you a idea of what your in for

http://www.differentials.com/install.html

Disassembly

Make sure that you have all the parts and tools you will need. The extent of disassembly depends on the job being done and the inspection findings. Lift the vehicle using an appropriate lift or a jack and safe jack stands. Always make certain that the vehicle is safely supported before working underneath. Unbolt the driveshaft from the yoke. Remove the differential cover or unbolt the third member. Let the oil drain into a suitable container. Please recycle your waste oil. Remove c-clip axles by removing the differential cross pin bolt and cross pin shaft, pushing the axles in and pulling the c-clips. Full float axles are unbolted at the hubs. Punch both carrier caps with identification marks so that you will be able to re-install them on the same side and in the same direction. Most carriers can be pried out of the housing with a pry bar. Further disassembly depends on the job being done. If you're changing the ring and pinion or the pinion bearings, remove the pinion nut with an air gun while holding the yoke, or use a long breaker bar and brace the yoke (bolt it to a long board) so that it can't move. Knock the pinion gear out to the rear with a brass punch, taking care not to damage the threads. Keep track of the location and thickness of all of the original shims. Pinion bearings must be pressed off. Carrier bearings can be pulled using a bearing puller. Internal parts (inside the carrier) can be removed as necessary.