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Shakiness when accelerating in passing gear at highway speed

I just had four new LT E rated tires installed (balanced). Alignment is good and did not require adjustment. Tires are correct size for the vehicle. I noticed during an extended highway trip yesterday that the truck (94 K1500 Suburban) seemed to shake or rather bump slightly when I was accelerating to pass in the sixty-five to seventy-five mph range. Almost seemed like driving on a fine washboard. I looked at the balancing weights which on three of the wheels appear to be nearly the same size. Then I noticed the right front weight is obviously larger than the other three. Could this be the problem?

There’s a bit of a story here. (Isn’t there always?) I bought the tires from one source (whom I would never trust to do any repairs) and had a shop I deal with regularly close to home install them. The morning after the install I went to check the pressure cold and discovered that the right front tire was a standard tire while the others were the LTs which the bill showed I had paid for. So I missed this when I bought them (they threw them in the back of the truck after assuring me all four were the same) and my mechanic missed it when they were installed. Now the tires do look almost identical but the lettering on the standard tire was black both sides while the LTs were white on one side. Of course the standard tire has a lower maximum psi rating. I went to the mechanic first and he admitted to noticing this but I guess it just didn’t register with him to double check to see if it was actually a different tire before mounting it?! I should say I am having second thoughts about using this shop in future, especially after they under inflated the tires at 30psi as well. When I told him I was running 45psi he looked at me like I was from Mars but then, upon checking his Mitchell Manual he says that yes, this truck should have 45 to 65 psi. Anyway the guys who sold me the wrong tire made good on the problem however they installed and balanced it and I’m wondering if they got this part wrong hence the vibration I’m getting at around seventy five. The work order from the guys who installed the tires also states I need two upper ball joints, pitman arm and left outer tie rod and alignment (which I understand is standard when doing this job). Now I had them show me this and while I’m no mechanic I could see the play in the ball joints was extremely minimal and pitman arm almost negligible (the mechanic had a lot of trouble showing me this had any play at all and admitted he had seen much worse). The boot on the left outer CV joint is also split and missing its grease. The cost to do the suspension work is going to run me about as much again as I paid for the tires ($700ish+) and the CV joint they say needs to be replaced because it will have been contaminated with dirt. That’s going to cost $300 plus.

I’m not saying the suspension is perfect but I think they are on a fishing expedition here and I am skeptical this is what is causing the vibration at high speed because I never noticed it until the new skins were applied. I have not yet approached either the retailer or installer - just trying to get my ducks in a row first.

If the problem happens while accelerating but not going the same speed steadily, my gut feel is that it isn’t the tires. They’d vibrate at that speed whether you were accelerating or not.

+1 to what lion9car stated.
If the vibration is only felt while accelerating, a bad CV joint could be the cause, but the allegedly worn front-end parts could also be a factor.

I favor the front end problems as the source of trouble. In addition I would look at ujoints and stabilizer links.

Thanks for the responses. I guess the improperly balanced wheel theory is a non-starter then?

I may have confused the issue re. the connection with acceleration. I only noticed the vibration during passing when I reached a speed of approximately seventy-five mph. Soon as I went back to cruise control mode (at around 68mph) she ran smooth as silk. The other thing was when I passed going up a hill the vibration was not nearly as noticeable. I suppose I should try sustaining or slightly exceeding the speed at which the problem appears and see if it persists. I did ask them to look at the u-joints because I occasionally hear a clanking sound when shifting from park into reverse out of my driveway in the morning but they said there was no play issues.

On the subject of wear on the life of suspension components and recognizing this varies enormously with the type of use, how long should I expect ball joints etc. to last under normal conditions (eg. staying on the pavement with the only obstacles being the odd unavoidable pot hole, overly recessed manhole cover, bridge expansion joint or parking lot speed bump)? I checked my records and the only suspension work is a new pitman and idler arm eight years ago (when the tires I just replaced were installed). Otherwise I am willing to bet the suspension is all original given the very low mileage on the truck (under forty thousand miles) when I bought it in '01. The only time I was ever off road with it was in the California desert and the worst thing I ended up with there was a bunch of scratches in my clear coat from the d****d mesquite bushes.

I’ll probably start with the CV joint but I’m still bothered by the fact that this vibration only seems to have showed up after replacing the tires…

I’d check the U-joints and CV joints (if it has them)

You know it might nit hurt to have them check the balance.

I had a similar problem after having had new tires installed on a 2003 Toyota 4Runner. The tire dealer isolated the problem to one tire and wheel. He moved the tire about 90 degrees on the rim and rebalanced. This solved the problem.

Just a follow up for everyone who took the time to comment:

I brought the truck back to the shop that installed the tires and had them check the balance on the right front tire. The same one the original retailer had to exchange, reinstall and balance because they sold me a standard and not an LT tire by mistake. As it turns out, my theory that the tire was incorrectly balanced has been proven right - and by a couple of ounces apparently. Certainly enough to cause the vibration I was getting at 70+mph according to my mechanic.

I would replace the cv axle they our about $100.00 for a rebuilt cv axle .