Piston Slap: New CV Boots? A Split Decision!

Sajeev Mehta
by Sajeev Mehta

TTAC Commentator Detroit Iron writes:

Long time no talk (I sound like a native American an Indian). (Yeah, not so much. – SM)

I have an 09 Outback with ~65k miles. I had noticed a bit of a burning smell after running it for a while and it was pretty strong after a recent trip. I thought it smelled like a belt slipping but when I popped the hood the two belts looked fine. After looking around for a minute I realized that the passenger side CV boot had torn and was dripping grease on to the cat. Checking the other side revealed that the driver’s side boot was also torn. Apparently this is a pretty common failure for scoobies. The Internet says I should be concerned if I hear a “popping” sound or the clunk associated with failing bearings. Luckily I am hearing neither. The dealer had a set price of $370 per boot for replacing the boots that the service manager somewhat disconcertingly blurted out almost before I finished describing the problem. The independent shop thought they could do both for less than $500 if the axles weren’t bad, but if they were bad then it would be another $450 per.

My question is this: Can I just get split boots from JC Whitney and pack them with grease or do I really need to have the pros fix it?

Sajeev answers:

The split boots are probably a great idea, Dorman makes good stuff for old cars when the OEMs can or will not. That said, I’ve never used split boots on my rides as I roll RWD only. But here’s the real problem: armchair analysis.

  • Do you think road dirt/debris lodged inside the boot will eventually eat the axle bearings?
  • Do you have any doubts to that question?
  • Is that your final answer?

Only you can answer that and decide what’s worth your time/money. The $20-something for split boots is a cheap fix that’ll probably work, as you mentioned the axles are neither clunking nor popping: now try it from a standstill with the steering wheel turned at full lock (i.e. full left AND full right) and listen for the clunk.

If that test works out, well, go ahead and use the split boots. They will probably extend the life of the axle long enough to justify their expense.

[Image: Shutterstock user Kritchai7752]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Sajeev Mehta
Sajeev Mehta

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  • Claytori Claytori on Jul 07, 2014

    No one had mentioned a "stretch-over" boot to replace the existing one. I have one of those on my car on the right side that has lasted for a long time. This must be done by a mechanic. But for the inner joint they can just pull the shaft out of the tranny after unhooking the ball joint and change the boot without removing the whole axle. I don't know how well these work with outer joints. I have used the glued split joints long ago, which I installed myself. This was due to a shortage of $. Done in March on my driveway using a hair dryer to keep things warmed up. That one lasted a couple of months. The second one lasted OK, but of course I had some practice and the weather was warmer. You MUST keep the grease away from the glue joint. If you are $ challenged and the car is close to being scrapped by all means give the split boot a try. Most of my FWD cars have survived with no problems to the CV joints or boots to ~200,000 miles and were retired for other reasons.

  • Blowfish Blowfish on Jul 09, 2014

    Dorman is not a bad alternative, I have installed 1 in a merc 300sd, still good when i send her to the crusher, even though the end cap came off, but the grease seems to be still inside and never added more grease in 1 yr. The 2nd one was a mid 80s camry, outer cv boot, is ok I guess I should have done it sooner. Still has some clunking when may hard turns. If u're handy and able to do it yourself, u do save a bundle. To slide out the 1/2 shaft in a merc is no simple task! A camry is not all that hard. the merc's was glued on, I glued one side slip her on and then glue the rest and wait for a day to cure. The strap do require special pliers, I went for some hose screw on clamps.

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