Automatic Transmission... Lurch?

[turbozutek]

I did the air-box mod today, I went out and it was +20'c and the flap was set to 'full hot'!

I decided to modify the procedure a little though and instead of adding dowels between the spring and thermostat, I did it by installing a fat o-ring around the thermostat body, so that the thermostat still works, but defers to ALL COLD at a much cooler temperature.



See the little black ring here? Take it off and stick a big o-ring in here, or two if they are thinner. Slide the black ring back over the thermostat and re-install. If it's almost there but not quite, another smaller o-ring can be installed around the recessed 'neck' of the thermostat where the pin comes out. Notice how it's shut to cold now!

Throwing it in the freezer, the flap moved over for partial hot at around +1'c and quickly moved back to all cold after five minutes of being out and at room temperature. Much better I'm sure!!

Test drive - this has made an instant +2mpg efficiency difference and it has also as predicted helped in gear changes. This may be the final part of the puzzle as I really think changes may be about as smooth as they are ever going to get now; keeping in mind this is a 16 year old box which has covered 130K Miles and has only just recently had the fluid changed!

I could go insane now and start renewing engine mounts in the quest for a perfect gear-change, but I really think it's 'good enough' at this stage.

The other job I did today (and I'm not sure this will have a bearing, but mention for completeness) was swap out the manifold to exhaust gasket, which was a complete buttock of a job made all the worse by the crappy nuts and bolts Volvo supply for this now!

Chris...

[jblackburn]

Interesting mod to the airbox thermostat - I don't know that anyone's ever done that! I'll have to copy that post to the airbox thermostat mod post.

With this particular transmission, you'll never get a "smooth as butter" gear change like you find on some new 5 and 6-speed autos. Part of that is in the software programming - they change up to the next gear quickly instead of "gingerly" (have you ever seen how slowly a BMW auto changes gear?!) and are more performance-tuned, and part of that is it's a relatively simple design compared to most newer ones. That also means the things are about as close to bulletproof as you're going to get from an auto transmission as well

Though if you haven't changed the transmission buckle and/or lower engine mount, they made a HUGE improvement in shifting smoothness for me. Mobil-1 synthetic ATF also helped a small amount with the rough change between 2 and 3 for me.

[turbozutek]

Interesting mod to the airbox thermostat - I don't know that anyone's ever done that! I'll have to copy that post to the airbox thermostat mod post.

I think it'll work more or less well depending on the health of the thermostat. Mine still works as it should partially (it's sunk in too much and it's lazy to respond) but I think if the thermostat was totally knackered then this mod would probably just get you permanent cold air. Nothing to loose in trying and worst case you get the cold air you want!

Though if you haven't changed the transmission buckle and/or lower engine mount, they made a HUGE improvement in shifting smoothness for me.

Yeah I wondered about that - when I first got the car the top mount was humped (aren't they all!?) and that probably put a lot of strain on the lower buckle... It looks OK, but I'm willing to bet it's probably less than perfect. If I see one cheap I'll maybe snag it!

Chris...