Hello all! I recently put an Edelbrock 1406 in my 65 (327/300). Everything seemed to bolt up OK and linkage went back together with no strain. Now however, the transmission holds in 1st gear til about 30 mph. Downshifts at about 5-10mph about like it used to. I've tried the modulator vacuum line on the left front port and on the rear center port (1/4" IP fitting) of the carb. Edelbrock indicates it should go on the rear port. Seems to work about the same on either source. Haven't tried the timed vacuum port on the passenger front side of the carb yet. Anyone famliar with this problem? Is this a linkage or vacuum problem? Carb seems to work fine. Car now starts pretty much "on the key". Hope ya'll can help. As always, your help is most appreciated.

Thanks!

 

There is an adjustable rod that runs from the transmission to the carb. Just remove the part between the carb and the rod that leads down to the tranny. There is a clip that holds the two rods together at a linkage point. Remove this clip and now you can adjust the nut that will change your shift point.

Turn the adjustable nut counterclockwise several turns and your shift should occur earlier. If you don't like it, clockwise for later, counterclockwise for sooner.




[Modified by 67435animal, 5:51 AM 1/4/2002]

 

Your modulator line should always be connected to a full manifold vacuum source so it can sense engine load.

 

John's right. My PG car was connected to a full vacuum port in the intake manifold to the rear of the carb. The carb did not provide vacuum for the modulator valve.

Bob

 

Bob is correct.
This is caused by improper adustment of the transmission kick down..
This controls the preasure in the trans and shift point.

 

Kickdown is controlled by the linkage. If you adjust the nut as I described above, that may solve your kickdown problem. Would I be correct in assuming that your upshift happens a little earlier than you like? Also, do you know that your modulator is working as it should? Did your car ever kick down?

If you want a later shift and (we hope) kickdown, you have to undo the clip and turn that nut clockwise. But, watch that you do not end up adjusting it such that kickdown takes your tach above 5500RPM.

Bob

PS-as I recall the chassis manual describes this adjustment also

 

Do you have the A.I.M.? The adjustment procedure is in Section M35, Sheet 9. Essentially, it says that with the throttle linkage at wide-open position (lever touching the dash panel), you pull the kickdown linkage rod forward until it bottoms out in the transmission, and then adjust the swivel at the carb end so it drops into the hole at the bottom of the carb lever. This should take care of your linkage adjustment, assuming the hole at the bottom of the carb lever for the kickdown rod is the same distance from the throttle shaft as it was on the original carb.


[Modified by JohnZ, 11:20 AM 1/5/2002]

 

Thanks John Z, Bob and everyone else! I appreciate your help! Weather is supposed to be good here tomorrow so I will give the linkage adjustment a try. Thanks to Magicmachines (Dave W) also for the help outside the Forum earlier this week. Also have to reconfigure some of the vacuum connections to get the modulator back onto the manifold vacuum. This car's not just a job it's an adventure! Glad to have so many excellent "guides" out there to call on! I was looking at that section of th AIM last nite John, Thanks!

Thanks!
Dave Z

 

Your modulator is probably OK. You can test it by changing the source of vacuum to one of the side ports on your carb (the one on the metering plate wilkl do fine). If your shift pattern changes, your modualtor is probably OK. Inexpensive to replace anyway.

You might e-mail Dave who started this thread since he had his vacuum to the modulator connected incorrectly.

Try the linkage adjustment first and see whether you get a change in upshift and kickdown.

 

What speed should the Powerglide shift at?

 

The shift point should vary based on throttle. When you give it full throttle from a stop, it probably won't shift until 55 or 60MPH (check tach fot < 5500 is the trick).

At lighter throttle it should shift earlier, say bewteen 15 and 25 MPH ususally.

 

Hi everyone! Thought I'd update you on the Powerglide. I followed John Z's, MagicMachine's, Bob's and other's tips on adjusting the kickdown linkage. On my car the lower rod (threaded at rear) spins in the swivel at the linkage juncture toward the dash panel once you lift the clip holding them together. I disconnected the linkage to the throttle lever on the carb and then pulled the transmisssion linkage forward as far as it would go (could hear and feel movement in the trans). I think the accelerator linkage may have been hitting the battery cable running across the firewall over to the starter and maybe not allowing the accelerator linkage to travel as far back as well. With the carb wide open (helpful spouse assisting), I had to bring the rod about 1/2" forward to get smooth insertion into the carb lever. Hooked everything back together and went for a ride. Car is now shifting up at about 20-22 mph under mild throttle. Feels much better than hanging in there til 30 under normal acceleration. I still have the modulator vacuum attached to the carb but will change that when I get a replacement intake manifold fitting to accomodate it. Mine only has the single-outlet fitting connected to the PB booster. Also changed the fuel sending unit yesterday and have a functional guage again. Thanks to Mike LaFevre (Grand Sport II) and others for pointers on that job. I believe someone said in a post on the thread about buying an early Corvette or the 65 GTO that if you buy the Vette yet get hooked into a worldwide community of fellow owners. Ya'll are proof of that! No doubt I'll be back for more help! Thanks everyone! Dave Z