engine/gearbox rattle

[muller]

I have a strange noise comung from around the back of the engine area...Was told by experts it could be the layshaft so had the gearbox and clutch overhauled, replacing all the beaings adjusting linkages and adding a new clutch....Now I have yhe car back and the noise seems to be louder,,,have heard of poston slap but it appears the noise only occurs when in gear and under acceleration... Any ideas ????? It is a 1994 sierra classic with the 1300 engine

[hohamlet]

I have had a 99 Jimny with a problem that sounds like what you are talking of. We had to change the chain in the tranfer box to solve the problem. If you have a 4x4 box you may want to take a look there.

[Phils]

Looking through past posts you'll notice I've had a knock/rattle on our '88 Samurai. The timing belt tensioner bearing was dry and noisy but didn't stop the noise when it was replaced (along with the timing belt). The alternator bracket had a missing bolt and a broken bolt and had obviously been moving around. Repairing those didn't stop the noise. Then I used a mechanic's stethoscope and narrowed the noise down closer to the rear of the engine.

I purchased the car from someone that had already changed the clutch trying to fix this noise.

I checked the oil in the tranny. More than 2 quarts low, I refilled with synthetic. Noise remained unchanged.

Because of posts here, I added an oil thickener (could've used STP but chose Bardahl brand, I think it makes no difference). The noise pretty much disappeared. "piston slap" was mentioned as a possible cause. Thickening the oil would cause that noise to decrease, and it did. Rod bearing knock could've been the problem and thicker oil would change that noise too. So what is it? Probably one of those two, my guess is the piston slap but only an overhaul would tell for sure.

Oil thickeners are cheep to try (<$4) and would help determine exactly (closer) where the noise is coming from.

Phil