Vehicule specs;
1999 Chevy Blazer 4x4, 4.3 V6, automatic transmission, ~250 000km

My mom complained about her blazer having wierd vibrations while driving. I went for a quick road test earlier, and noticed the following;

Vibrations seem to come from the rear of the truck, and are very noticeable.
Worst when accelerating from a dead stop, seem to be worst under "mild to hard" acceleration, and seem to be definitely worst between 10 to 60 km/h.
They seem to almost go away when in neutral.

I know it may not be very helpful as a description..

I went under the truck and did a very quick inspection, the U-joint near the rear differential is definitely on it's way out (one section of the + has a noticeable play). The Ujoint near the transmission seems to be solid.

I was wondering if a mildly worn out Ujoint could cause those vibrations. I am not familiar with RWD based vehicules (been owning Honda Accord's for the last 10 years..).

Thanks for your time!

 

Hi ALL. Lots of good info here. Wished I had seen this thread before going to mechanic. I told him today severe vibration from rear when accelerating so I mentioned u joints - not drive shaft. He tells me joints are fine, but my idle, pitman arm and ball joints bad. So he does all this and a wheel alignment. He even tests drives it. Am told "all ok". I pay close to 1000 for all of this.

I get on the road - same problem - and get this, fuel gague pinned to "low" (even with a 1/2 tank of gas and battery light is on.

So, I go back - and there it sits. Now they think perhaps it's something else.

I asked for a refund and explained i never had a problem with my front end. They think maybe a misfired spark plug - no mention of drive shaft though.

I need to call them tomorrow to check that. Unbelieveable day.

Thanks

 

For the vibration, it was the rear ujoint that was loose, not much, but enough to have play. I replaced both of them and it fixed the problem. They cost me around 10$ each and a few hours 2-3 max taking my time and enjoying my beers


For the fuel gauge issue, we got the same thing (low-full) going randomly, even if the tank is full. I suspect either a problem in the wiring, or the sending unit itself. Since it's no major issue and now the car is a spare vehicle, i didnt take time to find out the problem exactly.

For your vibration, if it's under acceleration, like i described in my previous post, i'd try to change the u-joints in the back (transmission to driveshaft-driveshaft to differential). It shouldnt be an expensive job at the garage, if you dont do it yourself.

 

Mechanic called me today - confirmed rear drive shaft was chipped and that ujoint was in fact bad. $429 - I told them to do it. Since they misdiagnosed this issue and did a bunch of front end work which i paid for I feel i should get a refund, a partial at least. Though, I was told that the pitman arm, idle arm and ball joints were bad and needed replacing becasue of "play in the wheel".

As far as the gas gague pinned and battery light on I agree something electrical. But, this magically happend as soon as my blazer left the garage, in fact as soon as I went to start it. It's just unacceptable. Tomorrow I pick up the truck, and if this pinned gague is not fixed I am going to dispute the total original bill of 983.00 for the front end work which was not causing the rear vibration.

Your thoughts?