Thud At 55 MPH

[srs]

First flush the transmission and get a software update, drive for 100 miles and check back.
Why would you presume 4th, probably 5th (overdrive, lock up)

i roll,
I strongly agree with JRL's recommendation to start with a transmission fluid flush if everything else on the drivetrain checks out OK. I had the same exact problem with my 1998XC which has the 4 speed automatic transmission. It appears you have the same transmission and I am guessing your owners manual recommends Dexron III fluid. When my 1998XC had the "thud" problem at about the same mileage, my trans was flushed with JWS 3309 fluid (expensive!! but done while under warranty per www.volvoxc.com/resources/how-to/index.php ATF Replacement Service Bulletin). It fixed the problem but I have always wondered if a flush with Dexron would have had the same affect. Please report back if you decide on the ATF flush and which fluid was used. If you have a 5 speed, JWS 3309 fluid is the only fluid that Volvo approves.

JRL,
The same link listed above will provide chassis No. information for AWD years which have the AW 50-42 transmisssion which I believe refers to the 4 speed. I believe the 5 speed is refered to as the AW55.

[Tyrant11429]

Mine has PRND321 also, but when I drive on the highway and it passes 55 I feel the last shift and boom she's in final gear, and smooth sailing, but my question is if its a 4 speed auto, why shift into final gear at 55, and not at 40-45? The 960 and altima(4spd auto) I drive shift into final gear a little after 40mph and its smooth sailing from there (sorry to keep saying smooth sailing lol) I know the v70r have the 5 speed auto cause they have PRND4321, and even in the oweners books it shows that. When I first got my car a few yrs ago and drove it home I felt the shift at 55 and I said in my head, this has to be a 5 spd auto or a f-ed up tranny lol. Maybe volvo messed up ??

Sorry to be off topic, but I'm getting the new nissan 07 altima with CVT tranny, no gears, test drove one and liked the cvt, except for the high revs when flooring. Be cool if volvo comes out with one, I know audi did a few yrs ago. Other auto makers are doing it now.

[JRL]

Mine has PRND321 also, but when I drive on the highway and it passes 55 I feel the last shift and boom she's in final gear, and smooth sailing, but my question is if its a 4 speed auto, why shift into final gear at 55, and not at 40-45? .

It would depend on throttle pressure.
Light throttle should be about 45 or so, heavier foot, 55 seems reasonable.

[Tyrant11429]

Sorry man, light or heavy Accel, it doesn't shift until 55mph for the final shift, and than the idle drops to under 2000rpm and its smooth. It bothered me enough to test it under all circumstances lol, and yes the tranny fluid was done. This is a mystery to me.... if its a 5 spd really thats cool, cause I drive other 4 spd auto and know how they shift into final gear fast or slow

[JRL]

Sorry man, light or heavy Accel, it doesn't shift until 55mph for the final shift, and than the idle drops to under 2000rpm and its smooth. It bothered me enough to test it under all circumstances lol, and yes the tranny fluid was done. This is a mystery to me.... if its a 5 spd really thats cool, cause I drive other 4 spd auto and know how they shift into final gear fast or slow

Seems a bit high to me.
I'm going over to the dealer now and if I remember I will ask my tech this question

[i roll]

I took my xc to the dealer today (Weidner Motors, Mansfield, 0hio) to see if they could shed any light on the thud.
The mechanic (Mike) hopped in and we went for a drive. After 3 attempts at creating the thud noise, my car finally thudded.
At the garage, Mike hooked it up to the computer to see if it needed a tcm upgrade. He discovered that this upgrade had already been done. He thought that a previous owner had the thud and tried to fix it without success.
He drained the transmission fluid which looked dirty and replaced it with 5 liters of Volvo transmission oil ($16.00/liter).
I asked Mike about flushing it and he said he recommended against it since it had 85,000 miles. He said the pressure from the flushing could cause problems.
Mike then test drove it (without me) and said the problem wasn't fixed, my car still thudded and that it has internal damage.
On the way home from the dealer (about 20 miles), I tried to create the thud and couldn't do it.
I remembered that some of you said for me to drive it 50-100 miles so that the fluid would circulate.
I'm going to drive it drive it more this weekend and see what happens.

ATTENTION JRL: When Mike punched my vin into the computer, it said my xc was a Asian-Werner 55-50 -- a 4 speed with a 5th. gear overdrive so he used the Volvo transmission oil intended for 5-speed automatic gear boxes.
This adds to the mystery.

[BillAileo]

FWIW: Volvo does recommend using the JWS-3309 fluid in certain 4 speeds showing problems.

Bill

[srs]

i roll
Could you ask Mike at the dealership to elaborate on the part about "pressure from flushing causing problems"? I am curious to know how pressure occurs. Is it from an external machine that pumps fluid through?
Thanks!

[i roll]

Hi Steven,

Yes the pressure is caused by the machine that flushes it through the transmission.
Mike said he would recommend against flushing because it has 85,000 miles. He said the pressure could damage the pressure plates and also could cause the transmission to slip. Mike said a few additional things that were way too advanced for me to understand.
So he drained and refilled it.
Since I don't know squat about cars, I didn't argue with him.

[i roll]

Thanks to the help of some of you, i roll is now rolling without THE THUD.
I've driven about 300 miles since my xc got a transmission fluid "transfusion" and it's been healed -- for now anyway.
Thanks again for your advice.