GMC 10048682 Crankshaft

You can Select Your Vehicle to check if 10048682 fits your vehicle.

Where a new or re-ground crankshaft is to be fitted, or the original one has been re-ground, the correct bearings must be fitted. The V6 engines require the rear main bearing oil seal to be fitted with the upper half seated on the cylinder block seat and the lower half on the rear main bearing cap with the lips turned forward. If two lips are available place the one helix forward. For the seal halves install the protector installation tool and lubricate the seal lips with fresh engine oil. Place the main bearings in the cylinder block and bolt the main bearing caps in place; apply engine assembly lube to the bearing surfaces. Be very gentle in placing the crankshaft in its corresponding location so as not to scrap the bearing surfaces off the journals. It is necessary to put a layer of brush-on sealer on the block mating surface and the related surface of the bearing cap while the crankshaft or seal should not be contacted. Place securing bolts of the main bearing caps on the crankshaft and onto the cylinder block in a manner to face an arrow on the bearing. Tighten all the main bearing cap attaching bolts to the prescribed torque, apart from the number 5 (L4) or number 3 (V6) main bearing cap which should be initially tightened to about 15-18 Nm. Gently strike the end of the crankshaft with a lead hammer if the rear bearing is not seated properly, then re-torque all bearing cap bolts to the prescribed standards. For crankshaft end play, push the crankshaft forwards and check with the feeler gauge the clearance between the front of main bearing and the crankshaft thrust surface. Last put in the rear oil seal and the flywheel to help rotate the engine during reassembly, for L4 engines place the Woodruff key into the slot in the end of the crankshaft then put in the crankshaft timing gear and be sure that the timed mark on the crankshaft and camshaft gears match.

It is advisable to inspect the end play when an overhaul of the crankshaft is to be done by mounting a dial indicator such that the stem is parallel to the crankshaft and touching one of the crank throws. Rotate the crankshaft to the rear and set the dial indicator at zero, rotate the crankshaft forward and read a value of the end play. If it go beyond the said limit, then check the thrust surfaces of wear; if there is none, then new main bearings may rectify the problem. Incase one cannot find a dial indicator, use feeler gauges, pull the crankshaft towards the front and ease the gauges in between the crankshaft and the thrust main bearing to get the clearance. Remove the main bearing cap bolts an eighth turn at the time until they could be pulled out by hand and the caps are often numbered from front to rear, thus these marks are useful for the proper positioning of the cap bolts. If unlabeled they can be marked by the use of a stamping die or a center punch. As mentioned earlier most of the caps are marked with a cast-in arrow symbol that points to the front direction. Tap the caps lightly with a soft-face hammer to provide the required clearance and you can easily lift the caps off using the bolts and ensure that the bearing inserts are not dropped when doing so. Lastly, remove the crankshaft from the engine and it is recommended to do it with help, then put back the bearing caps to their positions on the head of the engine, tighten the bolts with fingers only.

Examine the crankpin and main journal surfaces for scoring, scratches, or corrosion. If any are evident, the crankshaft will need professional regrinding.

Lift the crankshaft from the engine block with care to avoid damage, and then remove the rear main oil seal.

The main bearing caps must be reinstalled in their original positions.

If it falls outside the specified tolerance, replace the rod assembly.

Push the crankshaft as far forward as possible and use a feeler gauge to measure the gap between the front of the rear main bearing and the crankshaft thrust surface.

Measure at various points around the journal's circumference.

Gently tap the caps with a soft-faced hammer to separate them from the engine block, using the bolts as levers if necessary, and avoid dropping the bearing insert.

Once the crankshaft is confirmed clean, carefully position it in the main bearings, checking the main bearing oil clearance with Plastigage placed on each journal.

Install the caps in their respective positions without mixing them up, tightening the bolts in three steps from the center main outward without rotating the crankshaft.

By measuring at various points around the journal's circumference, you can determine if the journal is worn out-of-round, and take measurements at each end of the journal, near the crank throw, to check for taper.