99 4WD Suburban "clunk" and fuel pump "whine"

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- Groomer Driver
  
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posted
20 years ago

Wed, Dec 3, 2003 4:15 AM

I just bought a 99 4WD Chev Sub with 81K miles. Original owner took great care of it...a very nice truck. Rear end is the 3.73 but no locking diff.

Question #1 is that when I take off some a stop, I hear a mild "clunk" coming from what sounds like underneath the truck and just behind the drivers seat. It's a little more noticeable when I'm making a LH turn. Mechanic said something about something needs lubrication and it's fairly common on these trucks. He said he would do it when I have all the fluids changed over to synthetic (Mobil 1 oil and gear lube). Can somebody tell me what's going on in plain English?

Also, electric fuel pump whine from the back of the truck is pretty loud. On every 98 & 99 Sub I test drove I heard the same thing. Is this something to worry about?

Thanks in advance for any and all replies!!!

GD in WI

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- "Doc"
  
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posted
20 years ago

Thu, Dec 4, 2003 1:44 AM

Inline................

The slip yoke on your rear driveshaft is binding on the splines of the transfer case output shaft. This is a VERY common problem. Two solutions, replace the yoke with GM's nickel-plated job that'll run ya $400 or so; or you can yank the driveshaft, slop some grease inside the yoke and it'll be quiet for around 6 months.

Perfectly normal. If it STOPS making noise, then you can get worried.

Doc

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posted
20 years ago

Sat, Dec 6, 2003 2:24 AM

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posted
20 years ago

Sat, Dec 6, 2003 4:23 AM

One application of grease should last you that many miles. I use Mobil 1 synthetic grease; seems to hold up better than other's I've tried. In fact, last time I greased mine was December 02', about 20,000 miles ago, and she's just starting to get noisy again.

Doc

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- Marc Westerlind
  
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posted
20 years ago

Tue, Dec 9, 2003 6:36 PM

That's interting. I'll definitely have to give it a try.

I always assumed the clunk was free play in the rear differential. I owned three vehicles with the 10 bolt rear end behind a 4L60E, and they all did it. I never got it fixed on any of them.

If I blocked my wheels, threw the tranny in neutral, and got under the truck, I could turn the driveshaft a good 3/4" in either direction before the ring/pinion and spiders would be free of slack. I always thought this was a bit much.

-marc