2-1 hard downshift when warm

[fmugur]

Time to report back.
Some of you already know what I have been through with the transmission rebuilt but just to summarize the facts for a better understanding and hopefully it will help somebody with this undefined 2-1 downshift problem.

So, the transmission (5hp24) on my car got to a point a while back where coming to a complete stop it would jerk and feel like a big hit from behind. This was happening only when the car was running at the operating temperature and not while cold. Everything was perfect until the ATF was reaching getting closer to 90-100C. I tried rebuilding the trasmission following the DIY and help from great people on this forum (Phil, TriX5, CivDiv...) Although I did pretty much the same thing and follow the manual as close I as could after putting everything together I still had the same problem although I have to admit it was a little bit softer hit but not huge difference.

I just want to highlight that driving with this hard downshift for about a year damaged a few components in the driveline. The axels upper part got a play. The rear shaft also got a big play as well as the from driveshaft with extended splined that was replaced not long before that. I assume the chain in the transfer case was compromised as well and I replaced the transfer case all together with new shafts. So, my advice would be if you experience this 2-1 hard downshift fix it asap.

Now, it looks like what is causing this problem is not easy to pin point. Some claim that they only rebuilt the valve body, some only by increasing the rpms, some rebuilding the entire tranny and so on. In my case the VB was rebuilt along with the transmission but no luck.

Using the INPA I concluded that if I drop the transmission temperature below 80C I should be ok. Thanks to civdiv's DIY I was able to install the exact same transmission cooler on my car and it's been about month since and I have a smooth transmission. These days the outside temperature is lower and the ATF runs cooler than in the summer when I still had a very soft hold before was switching to 1st gear. Not noticeable by a normal driver it was just me because I am looking for a perfect tranny after spending time and money on it. I can say that for only $50 the 2-1 problem went away.

So, if you only have this problem on your transmission and you notice that it only happens when it is warm then instead of rebuilding the transmission you can try this trick. civdiv has been running this tranny cooler for a while and he hasn't reported any issues.

cheers

[SlickGT1]

Which cooler do you have, and where did you mount it? Did you do braided lines?

[fmugur]

Here is the thread. Although I had new lines installed last year I had to cut the return line to insert the cooler.
http://www.xoutpost.com/bmw-sav-foru...-cooler-2.html