Transmission swap aftermath -- lower fuel eco

[Reuben Lim]

Hi all, blew the autotranny on my 89 525i US version a while back, replaced with a surplus tranny from Japan and been using almost two weeks now. Am happy with performance, shifts are smooth enough with a bit of slight jerk from 1st to 2nd, something I had more of in the old tranny. Aside from this, perhaps some delays in upshift which makes for higher revs, but not too much of a diff to make an issue of.

My problem though is that fuel consumption is definitely up. Fully topped off, till the 3/4s tick, used to get 50 to 55 miles, now am down to 45 or even less. Used to get close to 150 miles till the 1/4 tick, now that's down to 110 or so.

Anything I should watch out for after a surplus tranny replacement? My indie mech who also supplied the tranny says I have six months to play around with it, info'd him re lower fuel mileage, he said to just observe for a while.

What adjustments if any can be made on the tranny, like to the valve body, to improve eco? Btw, when he put the tranny in, he didn't replace the old fluid as he said it was still quite clean. Should I insist on a tranny fluid and filter change? Also, are there any running in thingies to observe after a surplus tranny change?

[632 Regal]

do the reboot procedure if you havent so everything gets used to each other. Is the transmission the same as came out of it?

[Kalevera]

If the car is like the US M20 525s, the trans is hydraulic and doing a reset wouldn't change any adaptations.

Where did the torque converter come from? I'd be watching what the tach does, comparing that info to what it did with the last trans (ie - same rpms at cruising speed?)

Maybe they filled the trans with seawater instead of ATF!?! Just a thought ;)

best, whit

[Reuben Lim]

Actually I did ask him about the torque converter, he said the whole change covered this presumably from the same car as the replacement tranny, this is a whole assembly right? Noticed the whining sound I heard at back with my old tranny abated somewhat, understand this is because of the torque converter, so I took that as a sign this was indeed replaced. And yes, Jeff, this is supposedly the same tranny as my old one. Also did the reboot thing. About the seawater, oh no, I hope not! They could have put maple syrup and I wouldn't have known. So, should I insist on new ATF fluid and filter? Should I wear the leather pants I just got from ebay when I go over there and insist on new fluid? :p That post was a gas, btw...

Yup, there is a definite change in RPM-shifting pattern, can this be adjusted?

I was also thinking when they removed/replaced the tranny, they could have moved some stuff around that could have affected fuel economy. I still have this persistent problem with rough idle, which causes me to swap the old idle control valve with a newer one I got from the stealer whenever either gets fouled with this oily gunk. But that wouldn't have an appreciable effect on fuel mileage, just the idle right?

Incidentally, the plastic elbow thingy connecting to the idle control valve is cracked, they just put some silicon on this, but am going to the shop now and see if they can scrounge up a replacement. Cheers!

[Kalevera]

Actually, the kickdown cable could be misadjusted/messed up; winfred or bill probably have more to say on that -- beyond moving them around, I've never touched a 4hp hydraulic.


best, whit