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Date:         Wed, 3 Jan 2007 15:14:36 -0800
Reply-To:     Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>
Subject:      Re: Auto tranny with hard downshift into 1
In-Reply-To:  <20070103224537.62530.qmail@web33508.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1


The synthetic you are using may be too "slippery"- or maybe not "slippery" enough. The bands and clutch packs all require a certain amount of "grab" in the fluid. That is one of the big differences in Dexron/Mercon vs. Ford Type F and such. The friction modifiers are different, and can cause hard shifts, or mushy shifts, if the wrong one is used. Ford formulations are generally less "slippery", and give more positive shifts. A trick that is used in GM-based street/strip racing trannies is to add a pint of so of Ford-type to the trans fluid. It firms the shifts right up! Dedicated racers usually use a seperate additive blend, not included in the regular fluids.


  Look closely at the type of fluid you used. Maybe it wasn't the right one...?


  Another possibility is a hanging shuttle valve. Manual shift use a different fluid path, so the trans will behave differently.


  Or, maybe it is just a stubborn air pocket. Been known to happen...


  Try something else, maybe. Go to somewhere relatively deserted, and try this. Slow down to just rolling - not stoppped. Then, floor it. Just for long enough to get the trans to try to down shist. It should only be a second or maybe two. If the trans was still in second, it SHOULD kick back into first now. Was the full throttle downshift hard? It should be noticable, but not a slam. Valve body issues if it still slams, most likely.


Zoran Mladen <zmaninco@YAHOO.COM> wrote:
  Hey folks,


Our automatic has developed a strange symptom. Accelerating is no problem, starts off fine, upshifts no problem, everything is great. When you slow down, if you only slow down to 5 mphs or so, everything is still fine. Hard to tell if it goes all the way down to 1st, but there are no problems.


If you come to a stop, then you have a problem. As you slow down, you can feel the tranny downshift. As you come to a complete stop, and I think this is as it shifts into 1st, there is a bit of a slam when it does it.


I experimented by manually downshifting it to a stop. When you do that, no slamming. BUT...when you stop and then manually shifts back up to 2, THEN you get the slam.


Tranny fluid is synthetic and recently replaced...appropriate level, right at the top marker.


Any ideas? Could this be related to the 2nd gear brake band???


Z


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