Recently bought a 98 Forester with 5 spd and 2.5 DOHC motor, 145,000 mi. Nice car, but..... mysterious rattle coming from up front whenever power is applied in 2,3,4,5th gears. Can be light or heavy throttle, same sound. Sound alters slightly if you push/pull on the gearshift lever. Does not rattle when in First or Reverse. Does not change if turning or going straight. Does not rattle when coming down on compression. Rattle is road speed dependent-- rattles faster the faster I drive, regardless of engine speed. Checked all 4 halfshafts, and the driveshaft-- all seems well. This thing sounds like the front U joint behind the transmission is ready to come out of the car-- but all U joints are tight. The frequency of the rattle suggests driveshaft. Yes, I checked the oil in the gearbox-- level is OK, and gearshift feel is smooth, positive, and excellent. Put in new spark plugs-- no change. Engine runs great, with excellent power. Help!

Because you used the word rattle I think of heat shields. Everyone I know has had them rattle. The usual thing is climb under the car and hit the exhast with a dead blow hammer until you find it and tighten it up with and extra screw or whatever works for you. If it is more like a thumping sound that would be different.

Been under there-- all heat shields OK, both on exhaust piping and over the catalyst. Car is from Western Washington-- no rust under there, factory exhaust all the way back, including muffler.

Hey Doc,

Follow Cookie's prescription. Rust belt or not, get back under there with a hammer and tap away looking for a loose heat shield. It's tough to diagnose a noise over the internet but heat shield noise is a common occurence.

This may be a funny idea or not but have you looked at the shift linkage itself for rattles? My honda has a dirty rattle somewhere in the shift linkage due to worn bushings. It sort of comes and goes with certain RPMs and levels of engine load. If I grab the shifter it mostly goes away.

 

just something else to check anyway. good luck!

I'm thinking knock. Could be a bad knock sensor. Do you have a CEL on? if so, have the code read.

 

Try changing to high octane gas. If the problem is immediately better it engine knock for certain and you have a path to follow.

 

You could also try clearing the ECU to force it to re-learn the engine parameters.

 

I dunno

Isn't there a pilot bearing known to go bad on input side of the 5-manual trans?

 

**** **R***!

Here we go: http://www.endwrench.com/pdf/drivetrain/ShifterRattleInfoF99.pdf

 

Vehicles affected: '96-'97 OB & '98 Forester

 

**** *S****!

Thanks for the link and pdf file-- will replace this bolt and report back. I was suspecting it was something strange, 'cuz it only rattles in gears 2 thru 5, and you hear it from the transmission tunnel inside the car-- no noise outside. Again, thanks to all of you.

BTW, that's not the "pilot bearing" I was referring to in the previous post. I was thinking of something completely different there.

 

**** I*****!