Rear end fluid
 

My son has a 1991 Volvo 240. It has 190.000 miles on it. We don't know if the rear end fluid has ever been changed. I would like to get it changed and wanted to know what you guys think. Also should I do a fluid and filter change for the trans? Thanks in advance.

I asked the same question regarding the differential years ago and the general consensus was to leave it alone if you didn't have any problems. Maybe opinions have changed since then. On most RWD cars and trucks you should change it every 60,000-90,000 miles depending on the manufactures recommendation.

For the transmission I would just do a drain and refill every 30,000 miles which most people don't do anyways. The transmissions on our cars are made by Aisin which is basically Toyota and they are very reliable and durable. On transmissions over 100,000 miles it is best to not do a flush or even open them up to change the filter. It can stir up a lot of impurities causing problems that you did not have to begin with. I would only open the transmission if you have a problem with it. If its fine just do a drain and refill like I already mentioned.

the 'filter' on these is a metal screen. if you drop the pan, you inspect it, to see if there's junk on it, otherwise it goes back in.

ATF drain-and-flushes, I do every 60K miles or so. if the tranny fails after doing a flush, it was already broken, you just didn't know it yet.

oh, and changing the rear end gear oil every 100 or 200k is not a bad idea. good time to check the level, anyways, and its not hard to drain, just do it when the rear end is nice and warm from a long drive so its all stirred up.

Change those fluids! Old wives tale that new fluid will damage trannies with old fluid, started by shops trying to avoid responsibility in case a tranny fails after a change! Watch that rear end plug--it's very soft! Use a 6pt socket.

I do a flush on our 89 740 every 50K miles along with the timing belt change. Car has 355K on it now . Oh never changed the rear yet but will do that when I replace the speedometer pick up.

I did this a few years back on my old Audi Quattro - changed out both the gear oil in the rear differential and the manual transmission for some Redline synthetic (they have products to match all OEM specs). Made a huge difference on cold days...

Thanks for the input.