Aluminum vs Cast

Texas Z · November 14, 2002

I took my truck to be serviced today for the transmission shudder and of course question the engine knock. They still didn't fix the shudder (had to order parts) but did give me some new info on the engine knock. They gave me a TSB #01-06-01-028 which has been posted already. Anyways I was talking to the service manager and he said that the knocking has been around forever, it just sounds louder in the new engines due to the increased amount of aluminum used on the engines. I am no engine expert so I wanted to get your opinions. Is that BS or somewhat true?

bobc · November 14, 2002

I don't think Aluminum heads play much of a role. The blocks are still cast iron and have a water jacket to further insulate noise. Aluminum heads are far from new, just about all the imports you see on the road have aluminum heads clear back to the 70's. Many engines are all aluminum with iron liners. Also not new.

I would bet that the majority of the noise is passing thru the composite (fancy plastic) intake manifold. I'm not sure if the valley cover (under the intake) is aluminum or stamped steel. Either material would pass noise better than the heads or block for sure.

From this stand point these modern engines will always be somewhat noisier than older cast iron intake engines. Then again a "Noise Engineer" has probably spent quite some time trying to deal with the change too. Afterall, EPA regulates noise too. Maybe they need a better guy? :-)

Just my opinon.

later,

bobc

Markeaux · November 14, 2002

Well I can say for a FACT that my old 98 Z28 with the all aluminum 5.7 GenIII did not knock/tick - it was a smooth purring idle. But sure enough my 01 Tahoe 5.3 has a DOK DOK DOK DOK at idle whether cold, warm or hot.

silversport · November 17, 2002

Both my '92 and '99 Pontiac Bonneville had a knock on start up and the '92 had over 99K miles when last I heard, no problems...My '01 LS1 has the noise though... :angry:

silverado3500 · November 17, 2002

On the Transmission shudder, they did the tsb for my truck, however that did not fix the problem. The problem lies in the rear leaf springs. They are too soft when not under a load and the vibration that you feel is the rear wheels. I recently changed the leaves on my 02 1500 ex-cab to a 1 ton spring pack off a 2001 silverado dually. and that eliminated all launch shuddder.

While a 1 ton spring pack is a bit extreme to fix the launch shudder. For y'all who do a lot of towing a 3/4 ton spring pack might be the way to fix the launch shudder. Look for any springs from a 1500hd/2500/2500hd these are all 5 leaf spring packs. and these have an all around great ride even unloaded.

The reason for the 1 ton springs was for a better ride under a full payload (my truck is loaded down far more often then not.)