Volvo XC90 questions (help)

Hi guys, I was hoping yo guys could help me with some questions on Volvo XC90. It's my wife's DD, 2007, 3.2 AWD with about 105kmiles. Here are some issues I'm having:

1. The middle muffler outer steel layer literally peeled off. My mechanic changed it with an aftermarket muffler and now I can sell like something is burnt after the car is driven for a little bit. Is this common for new muffler or should I worry?
2. The transmission started to make a weird thunk noise when the gear is changed from P to R or N to R. When switching to D there is no issue and it shifts fine except once in a blue moon it'll downshift hard by itself (this probably happens less than 1% of the time). At the last service the indy Volvo shop I used to go to indicated that there was a small leak on the rear diff. They cleaned it up and topped it off and just asked me to keep an eye on it. Can the rear diff cause the thunk-ing noise when engaging Reverse?

Thanks for the input guys.

A fresh muffler will stink for a couple of heat cycles. Your thunking into gear will have nothing to do with the rear diff. Possible you have a squishy motor mount, but most likely the valve body is getting worn, or one of the solenoids is sticky. A high end trans shop can fix it, but it won't be cheap. A low end trans shop will cost more, long run, and the dealer will install a factory exchange. They will sometimes thump along for a long, long time... and sometimes they won't.

The clunk may be internal to the trans, or it may be the axle splines clunking around in the front hubs. Those chassis Volvos use a weeny little bolt tightened to something like 30 ft-lb to hold the axle in place, and if there is any slop in the splines, you feel and hear it. Volvo has a special highly toxic goop similar to green Loctite that they want you to use in the axle splines. RTV silicone works just as well and is a heck of a lot cheaper.

The shifting issue is probably sticky solenoids in the trans... it's a Volvo thing, they all do it, and you can usually go for 100-150k more miles before it becomes a serious problem. The S40 I just picked up has a 2-3 shift flare sometimes when dead cold. I think the reason nobody else using this transmission has these problems is because Volvo keeps the line pressure down for sleazy-greasy smooth shifts. Same trans in a Maxima bangs into gear.

THunk could also be the splined section of the driveshaft not greased sufficiently. I know with our toyota trucks it'll do that and that's always a sign to grease the DS, which always fixes it.

Streetwiseguy wrote: A fresh muffler will stink for a couple of heat cycles. Your thunking into gear will have nothing to do with the rear diff. Possible you have a squishy motor mount, but most likely the valve body is getting worn, or one of the solenoids is sticky. A high end trans shop can fix it, but it won't be cheap. A low end trans shop will cost more, long run, and the dealer will install a factory exchange. They will sometimes thump along for a long, long time... and sometimes they won't.

The indy Volvo shop I used said the same thing that it's most likely valve body although he hadn't seen valve body failure on the 3.2 engine. Will changing the transmission fluid help reduce the thunking when going into Reverse?

Won't hurt anything, as long as you use the magic (pricey) Aisan Warner fluid. There should be a reset for the oil life adaptation as well, but you need a good scan tool to do it.

Use the pricey A-W fluid or the torque converter will eat itself because it always operates at 50-200rpm slippage. And the Plutoxin-7 virus will kill you in 24 hours.

Our trans shop uses Dexron in everything. They warranty their work. They don't have problems. So, we use (synthetic) Dexron in everything. We warranty our work. We don't have problems.

disclaimer: No CVTs. But we've used it in VW DSGs without issue, too.

Likely cause….Splined shafts for C/Vs click on the volvos as a result of loose manufacturing tolerances that worsen over repeated cycling, fix is to remove them and locktite them. Don't run that diff dry or you'll regret it.

There's a little do-hickey at the bottom of the transmission that is there to reduce that thump. It wears out pretty quickly. Yours is quite likely worn out. Easy replacement and the cost is generally about $30. Think IPD identifies it as a lower transmission mount.