Transmission Shifting

[KenBourque]

Under moderate accelleration, the automatic transmission in my 1970 280SL shifts from 2nd to 4th bypassing 3rd gear.  I've checked the vacuum level and keep the engine well tuned but this occurs almost always when the speed at which the normal 2-3 shift point (at light throtle) would occur if the vehicle remains in 2nd beyond this shift point at greater accelleration.  What could be the possible problem?

[thelews]

I don't think it is a problem.  The 280 SL I was detailing did the same thing.  Surprised me at first, but then I learned how to throttle it so it doesn't happen (pretty much just a steady foot until the shift from 2-3, then lighten up if desired).  I also quite often used the gearshift to downshift to third through turns where it would usually stay in fourth.

[Mike Hughes]

Mine has done this on occasion, too.  Usually when starting out briskly and then lifting off the accelerator even the slightest amount while still in 2nd gear will almost always guarantee shifting straight to 4th.  So I've just taken to starting from rest in 3 and then shifting to 4 when up to speed.  The "backwards" autobox shift quadrant makes this 3-4 manual shift seem almost natural, just like the 3-4 shift on a manual transmission.

[thelews]

quote:Originally posted by Mike Hughes

Mine has done this on occasion, too.  Usually when starting out briskly and then lifting off the accelerator even the slightest amount while still in 2nd gear will almost always guarantee shifting straight to 4th.  So I've just taken to starting from rest in 3 and then shifting to 4 when up to speed.  The "backwards" autobox shift quadrant makes this 3-4 manual shift seem almost natural, just like the 3-4 shift on a manual transmission.

Start in 3?  Mike Phelps would beat you for the first 50 yards in a pool!

[Mike Hughes]

Regardless of whether the selector is in 3 or 4 the car still starts off in 2nd gear like always.  Starting in 3 is the same as starting in 4 except that the transmission is prevented from making a direct 2-4 shift - it can only make a 2-3 shift because 4th is blocked off. Then I manually shift it into 4th when I'm ready.

Michael Phelps could beat me to the end of the pool and trade in his goggles for a new pair before I even made it 50 yards!

[thelews]

quote:Originally posted by Mike Hughes

regardless of whether the selsctor is in 3 or 4 the car still starts off in 2nd gear like always.  Starting in 3 is the same as starting in 4 except that the transmission is prevented from making a direct 2-4 shift - it can only make a 2-3 shift because 4th is blocked off. Then I manually shift it into 4th when I'm ready.

Michael Phelps could beat me to the end of the pool and trade in his goggles for a new pair before I even made it 50 yards!

Oh, I should have realized that.  I have a manual.  Good solution to the issue.  So, you mean Phelps could beat you even starting in 2nd gear?  They are a bit ponderous off the line, unless you hit the kickdown to first, in which case you'll be disqualified for a false start!

[Chuck]

Hi All,
My 1964 230SL automatic shifts really hard, in that it stays in gear until the RPMs are quite high, then slams into the next gear. Is it a vacuum problem?
Also, since I had the top end replaced (new valves, keepers, springs, tensioner, followers, etc) the engine will start, but when warmed up will die, and barely run. The mechanic says he doesn't know what is wrong - typical!
Any suggestions?

Chuck