ZF 4HP22 tranmission servicing recommendations
 

My Volvo came with a large collection of service records and repair slips but in reviewing the large folder I cannot determine when the transmission was last serviced.Knowing this I think it prudent to drain the fluid and replace the filter. I do not have a green book for this information so naturally I do have a few questions:

1. Is the filter similar in appearance to the one in this picture? http://www.google.com/imgres?client=...1&tx=134&ty=90
2. When shopping for filters I've seem some come with and without a filling tube, can I re-use the old one on the new filter? If so, do I need a new o-ring or seal for the tube on the new filter?
3. What fluid should I use?
4. If I'm dropping the pan to replace the filter I plan to replace the same amount of fluid I removed. I reckon this is a decent method?

Thank you for the replies.

This is a little embarrassing, but I usually replace the whole trans.there is some point to pulling a cooler line, and running the engine to pull clean form one bucket while exhausting dirty into another. you only get 1/3 of the fluid out dropping the pan.
DexronIII or better

I wouldn't replace the filter. Should be good to go with a visual inspection. There was a later Volvo tech bulletin that stated not to replace the filter. Reverse blow w/ shop air (messy!).

Clean well the pan and magnets. Note the clamps are different for the corners. Don't overtorque.

745 TurboGreasel reminded me of a method I have used in the past to flush all the ATF, which worked well.

Not wanting to admit it, but I used Supertech Dexron III from Walmart. And 1/2 to 2/3 bottle of Lucas Trans Fix, to atone.
http://www.lucasoil.com/products/dis...iid=29&catid=2

Why wouldn't you replace the filter?

Does the torque convertor hold the remaining 2/3rd's of the fluid?

The filter is just a mesh screen, not a filter per se. I don't see a reason necessarily to *not* replace it though. Wonder why Volvo would have recommended blowing it out instead?

You can find a kit that includes a filter, O-ring, and pan gasket as a set, this is the easiest way IMO. Tranny service is worth doing, I like to know what it looks like inside the pan anyway. I have used the "transfusion" method as well. Never tried putting an "in" hose in a clean bucket as well as the "out" hose in the dirty bucket to receive old fluid -- I'm not sure it works that way, haven't ever looked at the tranny diagrams but I have always just done it by letting it pump old fluid out a cooler line and adding new through the dipstick tube. I don't know if the trans will "suck" from the other side of the cooler or if it just returns from the cooler circuit back into the sump under pressure from the feed side.

The times when I have wanted to really thoroughly refresh one, I usually start by doing a pan/filter service, drain all fluid out from that point, clean pan and magnets, make sure everything looks cool in there, reseal with new gasket, and fill with new fluid, *then* begin the transfusion process after that. This way you start the job already halfway done and don't waste as much new fluid mixing it in and pumping it out with the old. Good to do this part with the rear wheels off the ground and trans in neutral since ZF doesn't like prolonged idling or revving in P or N when the output shaft is stopped. This way you can just let the rear wheels spin if they want without having to worry.

Seems like most wisdom about these is that synthetic fluid is not worth the money, better to use DexII+ fluid as cheap as you like, and drain/fill often to keep it clean.

297k on the original unit in my DD, still does what it's supposed to, though the 1-2 shift is a little firm at part throttle. They can last a long time if cared for. :)

Kit
 

Search part # 24341ZF4KIT

E.g.: http://www.gowestyautoparts.com/OEM/...+34+1+ZF+4+KIT

Just so I have this right I would disconnect a line going from the transmission to the radiator and place into a bucket. Then start the car with the rear wheels raised and in gear. At this point transmission fluid will start draining into the bucket, presumably a "dirty" color. As it drains I replace with fresh fluid via the dipstick hole?

Do I keep this up until the fluid exiting the transmission is a new/clean color?

How will I know how much fluid to add during the process?

No need to put in gear, it charges the torque convertor regardless of selected range.
I'd do the pan n filter first, then do this for about 2/3 of total capacity.

Yep. I forget whether the ZF feeds the fluid in at the bottom or the top cooler connection. I would unscrew the upper line connection and run hoses from both the cooler line and the cooler barb on the rad into your bucket -- that way whichever one it comes out of you will be covered. I guessed wrong once and it makes a big mess...

Transparent nylon hose is nice to use for this so you can see when flow starts and get a better read on the color of what is coming out. In the bucket it always looks dark even when it's clean.

What 745 said, leave it in neutral, doesn't need to be in gear, just a good idea to have the rear wheels free to turn while it's idling in N. ZF autobox can burn itself up by partially applying the forward clutches when in neutral with wheels stopped if left to idle a long time that way (or worse, revved).

In WA State lots of ZF transmissions got blown up back in the day due to this syndrome during emissions testing, where an operator would have to hold ~2500 rpm in neutral for a few minutes. Legend is that many of those cars (Jags, BMW's etc in addition to Volvos) never drove out of the test station and the state had to buy a lot of transmission rebuilds, until they eventually made cars known to have ZF transmissions exempt from that part of the test!

Just idling rarely hurts them, but keeping wheels off the ground lets them spin if they want to, which saves the tranny from eating itself if it is trying to make friction.

You can make a rough guess. Some people like to use some kind of graduated container (e.g. oil or coolant jug) so you can get a read on how much it is pushing out, or you can eyeball it. I usually run the engine for a minute or so, stop, add a quart or two in thru the dipstick tube, repeat, until the fluid is coming out the hose looking clean and new. Usually takes a few gallons to do the whole thing. As long as you don't overfill it during this process, once you're done and have everything buttoned back up you can check and top off the tranny fluid level in the normal way. You just want to try to pour in pretty much the same amount that is coming out, or maybe a little less, but not too much less. If you start seeing air bubbles or foam coming out the hose at any point while flushing it that means you let it get too low, shut it off and add more.

Usually you get a nice noticeable improvement in shift quality after doing this. I notice it especially in TC lockup engagement -- much smoother. :)

It's also confusing because fluid reverses direction during TC lockup.