I have a 1993 Chevy suburban show truck and it wants to red line at 40 to 45 miles a hour .It shifts out of 1 st but in 2 ND it goes to 45 are so then it jumps in to redline ..

This may sound simple, but start with the linkage issue first as this is the easiest and simplest item to do. Usually, when transmissions issues arise, it is with synchronizers or bearings. A very rare case would be a clutch not fully disengaging can cause shifting problems as well.

Kickdown cable unhooked, attaches next to accelerator petal cable.

Yes you should because it was not what truly evaluated with the concern that you have

Hi : ) Sounds like the third and fourth gear clutch pack has burnt out or there is some valves in the bottom of the transmission not working properly time for a mister transmission to look at it. If the fluid is up on the stick when it is warmed up that good but if it has brown colour in it that not good it should be bright red and see throught.Here is a Diagnosis Chart

sound's like u need to check the tranny fluid? how many kilomiter's on the truck and the tranny?

That should be the L60-4 truck version
Have the sedan version, 93 Caprice.
That was the first year of the new electronic shifting transmission.
Especialy when cold she will shift hard, but it's normal.
But that depends on what you call normal.
I have gotten used to it over the last 17 years.

check fluid level AND condition...should a red color...if its discolored, in any way, flush it and change the filter too...then perhaps there is a band that is out of adjustment allowing the flare up, and it suddenly grabs getting the hard shift....or else trans is worn out....check the fluid

Try and adjust the down shift cable..Sounds like either it is broke or out of adjustment..

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

Is your driving primarily city?
You may want to check to see if the clutch master cylinder reservoir is full. If it is not full you may have a leak or the clutch friction disk is worn. If the fluid is at the correct level, you might consider having the fluid flushed and refilled.

rebuild the original, a 95 wont and cant work, and it a 2 wheel drive if the shaft is too long... www.TransmissionGarage.com