[george w]

The throttle pressure cable is adjustable. There's a black plastic collar at the base of the cable where it attaches to the trans. There is a built in latch in the center top section of this this collar. The service manual refers to this latch as the "Cross-Lock". This center section can be popped up with a screwdriver which will allow the cable to be adjusted.
Exerpted from the shop manual, edited by me:

1.Engine should be at normal operating temp.
2. Loosen cable bracket lock screw that secures the bracket to the trans, case.
3. Position the bracket so that both bracket alignment tabs are touching the trans. surface.
4. Tighten the screw
5. Pop up the Cross Lock latch with a flat bladed screwdriver.
6. Let the trans. cable slide all the way toward the engine until it hits against it's stop.
7. Rotate the trans throttle lever fully clockwise against it's internal stop.
8. Press the Cross Lock latch back in.
9. Check the throttle lever range of motion by rotating it fully counterclockwise and release it slowly to confirm that it will return back to fully clockwise.
Small changes in this cable setting have a major effect on the transmissions upshift and downshift points.

 

[mopar56]

thankyou I will try it!

 

[ImperialCrown]

The adjustment may not be the problem and shouldn't really change once set (unless an internal wear problem needs to be compensated for).
This cable and bell-crank could bind at the throttle lever slot at the throttle body and at the transaxle kickdown lever underneath the battery tray. Battery acid wash and misting had a likelyhood of corroding the metal around it, especially underneath it with dissimilar steel of the kickdown/shift lever shafts and aluminum case. Make sure that the kickdown cable lever moves freely and springs back to the closed throttle (idle) position.

 

[Bob Lincoln]

I'm betting that your air intake modifications are snagging on either the kickdown cable or some part of the throttle body assembly.

FWIW, all cars have cold air intakes from the factory.

 

[mopar56]

the cable seemed free on the throttle lever but I will check again, as far as the cold mod goes, there is nothing interfering with the cable, its very clean and simple with nothing at all around the linkage

 

[Bob Lincoln]

Is the custom airbox touching anything?

 

[mopar56]

no, it all sits to the passenger side of the engine, where as before with the stock box the throttle and shift kick down cables were covered, all I was thinking with the modification was the air/fuel mixture would be denser possibly causing it to effect the shift but that seems like a stretch, I just performed the adjustment listed above, it was actually quite simple to do, I also checked for the kick down cable moving freely on the throttle lever and it was and I sprayed a small amount of wd40 on it as well, also I checked the bell crank on the trans when I did the adjustment and it was also free, so my son is taking the car to work this afternoon and I will find out when he gets back if it made a difference or not and report back, thanks

 

[mopar56]

FIXED!, thanks George W and all who helped, the trans adjustment I did yesterday as per the guidelines listed above did the trick, you were right the smallest adjustment made a huge difference!

 

[george w]

Glad to hear it's fixed. Been there and done that several times. It doesn't take much of a mis-adjustment to throw the upshift points off.