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75 Eldorado - Replaced Carb- won't shift

Started by pplaut, June 20, 2018, 06:07:33 PM

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pplaut

I replaced the carburetor on my 1975 Cadillac Eldorado. The engine runs much better. However, the car will no longer shift out of first gear. I checked the transmission fluid- levels appear fine.
Thoughts?
Thanks!
~P
Peer L. Plaut
Head Baldie
Baldmen.Com

bcroe

Perhaps your kickdown switch on the throttle side of the carb is stuck
in WOT kickdown mode.  Try pulling off the electrical plug and see if
it shifts normally.  If so the switch needs some adjustment or more. 
Bruce Roe

chrisntam

Or a disconnected vacuum line to the vacuum modulator?
1970 Deville Convertible 
Dallas, Texas

35-709

That will do it.  Check that line from the back of the carb all the way to the modulator.  There will be a rubber hose at each end and a steel line in between (if it is anything like RWD).  Also check the modulator itself, if you pull the hose off the modulator and get trans. fluid dripping out of the modulator or the hose, replace the modulator.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

bcroe

The missing modulator vacuum hose might be the most likely, but I
suspect the trouble is close to the carb since it was just replaced.

Bruce Roe

pplaut

Thanks guys. I will check the kickdown switch as it is pretty easy to get to. I did replace the vacuum line from the carb to the steel line to the modulator. I did not confirm that the steel line was unplugged on the other side!
Testing now!
Thanks again!!
~P.
Peer L. Plaut
Head Baldie
Baldmen.Com

Scot Minesinger

It is for sure the vacuum modulator not hooked up.  Trace the line up from modulator and verify it receives vacuum.  Then test vacuum modulator to make sure it is good. 

The kick down switch shifts the car from either 3rd to 2nd or 2nd to 1st under heavy throttle, so for this to be a problem you need to be in 3rd gear driving about 50mph, and floor it with no down shift.  Often the kick down switch is not understood and damaged by mechanics during carb work, but the car would still shift out of first gear.  However if the vacuum modulator gets no vacuum (it is connected to carb), it will not shift out of first gear.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

pplaut

Well, the easy thing was the kick down switch. I unplugged, no shift love. Now to the modulator and vacuum, etc.
I don't doubt the kick down switch has problems, but I can always move the lever by hand if necessary. But I need to get the thing out of first gear first!! LOL 8)
Peer L. Plaut
Head Baldie
Baldmen.Com

cadillacmike68

Reminds me of the little nash rambler song.

"how do i get this thing out of second gear?"
Regards,
"Cadillac" Mike

pplaut

Replaced the vacuum lines- still not shift. On an interesting note. Is it possible transmission fluid could be coming up through the fill stick?  There appears to be leakage up top spilling down onto the manifold.

I have done nothing with the transmission at all except put the thing in drive. One thing I noticed is, before putting on the new carb is the car would not always go into park. The shift lever would go all the way over, but the car would still roll. Moving it between Drive and Park it would go in. Why do I have a feeling the tranny is shot on this beast? I am going to order a new modulator just for the hell of it. 66K miles and will check the vacuum at the carb... not sure what the vacuum pressure should be. Any ideas?
Thanks!
~P.
Peer L. Plaut
Head Baldie
Baldmen.Com

bcroe

Now the thought is a bad trans.  Do be sure the speedo is working,
if not the plastic governor gear is probably stripped, replacements
on Evil Bay.

There are rubber seals on the clutch
pistons and other parts, I would not run the originals more than 2
decades. A $30 soft kit will replace them and save your trans from
serious damage before long.  Of course the labor cost is nearly the
same an an overhaul if you don't do it yourself.  If you saw parts
this age I have removed, you would understand. 

Try a filter replacement, check fluid level.  If you DO get a trans
refresh by a shop I would ask to retain as many of the original
hard parts as possible, esp the torque converter and steels.  I
have had too much trouble with "NEW" but inferior replacements. 
Replace the Torrington thrust bearings.  Bruce Roe

TJ Hopland

I wasn't going to say bad till you said fluid coming up the stick.  That's never a good sign.  I'm with Bruce, 43 year old seals and clutches.   

Its fairly common in this era Eldo to have significant wear in the shift linkage so the not going into park thing isn't that unusual.   There were a couple different designs of the 'crank' arm and bushings so GM apparently knew it was sometimes a problem.   Neither design seemed better than the other one.   I think they just wore if the car wasn't parked on a perfectly level surface and it takes a slight amount of force to shift.   I was able to fix mine with some slight fabracobbling using bushings from a universal door hinge repair kit.

Fluid coming out the dipstick isn't a good sign.  It should never be anywhere near that high.   

If you unplug the electrical connector from the side of the transmission that will eliminate the 'kickdown' switch and circuit.   That gets a +12 voltage to engage so no wire no voltage which means the trans runs in normal mode.

The vacuum modulator is the load sensor so to speak.  Idle and light load cruise vacuum is high typically in the teens.  Wide open or heavy load vacuum drops to zero or single digits.    So when the transmission modulator is seeing teens its normal mode.   When the signal drops it assumes you are wide open and or heavily loaded so it goes into that mode which delays and firms up shifts.     

If you had that +12 signal and no vacuum I think it would eventually upshift but no sane person would ever push it that far so it would appear to most people its stuck in first.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

pplaut

Thanks to ALL- New modulator- did the trick - of course, there is the while you are at it syndrome that catches up with most of us. I pulled the pan, cleaned it up very well. Replaced the filter. If there was fluid coming out from up the dipstick it has stopped.
Again- thanks to ALL!!!
When my new exhaust comes in I think she will be running like a scalded dog.
Peer L. Plaut
Head Baldie
Baldmen.Com