My 1996 Ram makes a awful screech when I accelerate. I noticed that my crank pulley moves about 1/2 inch foward when I press the gas. Any suggestions?

 

Is it a metallic screech or a rubber type screech sound? The crank should not be moving a half an inch as it is fixed in place between the end bearings. Plus, all your piston rods are connected to that as well- so, that movement of a half an inch would be causing more than just a screech sound. Mechanically, you would be in some real trouble there if that were the case.

However, what may be happening is, your harmonic balancer is sliding on the shaft due to a loose crank bolt. I would remove the serpentine belt and then by hand, feel for movement on the harm bal and pulley assy. It is supposed to be a tight fit as it's usually removed with a harm bal puller and put back on by pressing it on. It just doesn't slide around unless something is very worn out or the key is damaged or badly worn but, it will when the engine is rotating under load due to centrifigal force. Then, when the idle comes back down, the belt tension re-aligns it with the other pulleys. But, if you see that much movement and your 100% positive about this movement, it sounds like it's loose and needs to be tightened up to OEM spec immediately. IF it is loose to the point where you can wiggle it by hand; something is worn and should be serviced. If your not able to move it by hand, it just needs to be re-torqued and you can be on your way.

Now, if you check for movement and notice that the pulley and harm bal are NOT moving but, the entire crank is- you have a problem. This means, when you lay under there and watch the movement while the engine is running you see that the entire crank is moving with the balancer - you have a problem. Have someone rev the engine a little at a time until you see movement. Note what is moving. Also, you may want to look at the pulley bots and check to see that your pulley is not loose.

If there's nothing loose, and, you were mistaken on the movement, then, it may just be your belt in which case, you should replace it or, you can apply Gasgacinch as a belt dressing and that issue will disappear immediately. However, usually a screeching belt is one that is dried out, cracked and glazed over. It should be replaced anyway. Be sure to check all of your pulley assys while your at it.

How many miles you have on that engine?

 

Thanx a ton. Theres 97000 on it and I tried to tighten the Harm Bal and it was very tight. The whole pully jumps out when accelerate. I had a mechanic look at it and he said he's never seen one do that and stay in tact and with an engine that sounds perfect

 

somethings wrong.

with engine off, if you get under the truck with a crowbar and GENTLY pry back and forth on the balancer, where is the movement coming from. the entire balancer, both the inner and the outer sections, or is just the pulley loose on the balancer.

there's only supposed to be a very small amount of in/out play on the crank. i don't remember what its called, maybe runout?, but it should be a small amount, something like 100'ths of an inch.

how much in shadetree terms y'all think it is ? maybe 1/16" ?

the crank can slide some on the mains, because the pistons can slide on the wrist pins. but i've never seen it move 1/2".

unless the crank was broken, but i'd think that would knock like a mother.

if the crowbar pry moves it a lot, remove the belt try again and ... heaven forbid .... see how far the sob will slide. i hope your crank isn't broken.

 

Crankshaft end play should be .002 to .007 of an inch.

 

I have 221K on mine and nothing like that has ever occurred. There is something out of whack for sure. If it's not a loose harmonic balancer and, if it is not a loose pulley- (you checked the pulley bolts I assume) then, you have a major problem in the low end.

Now, we look at the problem in a way to troubleshoot the issue. When you checked your crank pulley, were the bolts loose at all. If not, then we look at the crank bolt. When you checked to see if it was loose, were you able to rotate the engine when tightening that bolt? It only takes about 30-35 ft lbs to rotate it. It should rotate fairly easy. If so, and the bolt was not loose, the only other possibility of movement of that magnitude would be a snapped crank. The break would also have to reside towards the front of the engine in order for it to slide out that far. A half an inch is huge and no wonder it's screeching.

Here's what I would do. Drop the oil pan and just simply look at the crank- providing you double check all else. Then, you will see what the issue is.

Good luck. CM