defiant1

Ok, I changed my carburetor and throttle linkage and now my shifting pattern is upshifting "all in" by 45mph.

Current setup: Speed Demon 750DP mechanical secondaries with Lokar throttle linkage.
Old setup: Qjet with repop throttle linkage.

Under old setup I could "load up" RPM between each upshift. New setup has initial load up but instead of allowing more RPM at each shift point it continues through all upshifts before I reach 45 mph.

Thoughts?

d1

P.S.: I am not looking for any carb advice, I have invested over $1000 in Qjets (tuned by "experts") over the years and they all had problems. I used the Speed Demon as I had it on hand and was tired of trying to make Qjets work at this junction. Maybe I will try to make a Qjet work later on, but as of right now I can at least drive my car which I couldn't for the last 4 months due to incorrectly working Qjet.

ach1992880

Make sure your "kickdown cable" is still installed on the car. On my '71 it was actually attached to the throttle pedal inside the car, but I know a lot of these were replaced by generic carb-linkage cables over the years. If the transmission doesn't receive a pull on this cable during accelleration it doesn't know to increase pressure or increase shift points.

defiant1

I did ensure I hooked it up. As I removed the pedal to make installing the Lokar clevis pin easier. Not much too it, plastic grommet the cable slides into.

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droldsmorland

Does the modulator line run off the carb or the intake? Should be on the intake. Is the modulator line intact down at the mod. You may have disturbed it. You've changed 3 things so the problem en lies there somewhere, the linkage or the carb/vacuum.

defiant1

I have it hooked to the intake manifold. I will have to follow it down to the modulator to make sure nothing was disturbed.

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joe_padavano

Well, first of all, I suspect that your "shift pattern" is still PRNDSL, so I don't think your shift pattern has changed. What may have changed is how you have connected the vacuum modulator. The modulator must see straight manifold vacuum to operate properly. It sounds like you have it connected to venturi vacuum that is high at large throttle openings. Vacuum must be low at large throttle openings for the trans to delay upshifts (which is what I think you are trying to say you want).

defiant1

Thanks for patronizing comment. I used the term "pattern" to describe how the TH350 allowed the SBO operate in a range of speeds while providing a wide range of output.

As I mentioned in a previous post in this thread, I do have the modulator connected to the intake manifold for its vacuum source.

I verified the lines are connected correctly, so I am back to my original concern.

Back to your advice, is it possible the carb is affecting the vacuum the intake manifold is supplying to the modulator (transmission)?

If not, then I am looking for additional troubleshooting advice.

d1

MDchanic

Which is fine, so long as you understand that nobody else uses it that way.

I believe that what you want to say, in the conventional idiom, is that your upshift points have moved lower since you changed the carburetor.

Things that could cause this include a vacuum modulator receiving too much vacuum, or being stuck in its "retracted" position, a governor not opening properly, and (if it's a full-throttle problem) a kickdown cable not connected or adjusted properly.

You could check the modulator by disconnecting the vacuum line for it and driving around the block - the car should shift high.
You should be able to rig a piece of string or fishing line to the end of the kickdown cable and driving down the street. If you pull the cable out, the transmission should drop one gear (the TH400 can drop two gears on kickdown, which is one of the ways it is different from the TH350).

- Eric

defiant1

Can you elaborate on the adjustment for the kickdown cable? I found it in the CSM but I am not clear on my reference point on where I am measuring to establish the tolerance. I have the 1970 kickdown cable with the "metal clip" at the pedal end.

Trying to figure out how the kickdown and throttle cables work in conjunction with one another. If the kickdown cable has limited impact on upshifts, then I need to find out what is affecting the vacuum going to the modulator.

d1

MDchanic

Not effectively, as I've never actually done it myself.

Essentially, though, there is a certain point at which the cable triggers the transmission to kick down, and the cable should be adjusted so that that point is just before the gas pedal gets to the floor.

- Eric

defiant1

Adding one more post to see if anyone has any more advice before I attempt to adjust the kickdown (downshift) cable. I appreciate Eric's advice above, just looking for a detailed (pictures, etc.) explanation before I tear into it tonight.

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oldcutlass

This thread will help:

https://classicoldsmobile.com/forums...cutlass-s.html

defiant1

I had reviewed this thread once before, but it doesn't address my setup. The kickdown cable doesn't have the long black plastic tube as described in the link you posted. All it has is the metal clip at the end of cable. I need to figure out how/where that it adjusted when pedal is at WOT or exactly where I am starting at for the initial adjustment as indicated in attachment.

ach1992880

The important thing is that at wide open throttle the kickdown cable is pulled to the limit of its travel. My original was frayed and had the end pulled off (hence not operational) when I bought the car. Bought a new cap to crimp onto the wire and with the help of a friend located the position that the crimp needed to be to pull the kickdown tight at WOT. worked great until I decided to ditch the engine/trans for a different setup (which I won't mention)

oldcutlass

I know some members have crimped a lead fishing weight on the cable to get their adjustment right. Some have gotten the clip from other members on here.

defiant1

Well, it wasn't as bad as I thought is was going to be. The metal clip at the end of the cable is actually a spring clip, which makes it a whole lot easier to adjust versus being crimped on (like I originally thought it was).

Car shifts notably better now after adjustment. After installing the Lokar cable the downshift cable had about 3/4" play in it that needed to be removed to operate correctly at WOT.

Thanks for the advice everyone.

d1