89 K5 Transmission Harsh Shifting Issue

[Lov-2-Rev]

Hey everyone,
I recently had a transmission issue crop up in my Blazer and was hoping to find a little help here.
It's an 89 with a 350 and OD automatic (700r4). Bone stock with the exception of long tube headers, full 3" exhaust and adjustable FPR.
I was out on a 40-50 mile run on local 2-lane roads and out of the blue, the tranny started hang-shifting on the upshift...1-2 and 2-3.
Truck doesn't get a lot of use. Only during inclement weather and summertime beach 'wheeling.

I've been chasing a rough running issue (running rich) for a while and finally got it smoothed out a few weeks ago.

Recent work I've done:
Rebuilt TB
New coolant temp sensor
New EGR
New MAP sensor
All vacuum lines inspected

Specs and Symtoms:
-Trans is a Jasper rebuild installed by a PO.
-Has a minor leak at front of trans and was noted as being 1 qt. low when problem started. Has since been topped off.
-Fluid is clean and not burnt.
-Shifts are crisp...no slipping.
-Won't up-shift without hitting WOT and then a slight deceleration.
-Won't shift properly in OD, D, or manually. P, R, and N all function properly.
-Once in 3rd, converter goes into and out of lockup properly.
-TPS appears to function fine as engine acceleration is smooth across entire RPM range.
-TV cable appears to move smoothly. (no recent adjustments)
-Issue happened for about 5 miles. Then I stopped for gas. After leaving, it worked properly for the last 20 miles of the trip.
-Next day it started off hang-shifting and hasn't cleared up again.

Any insight from the transmission guru's here would be greatly appreciated!

Thanks,
J.D.

 

[76k5blazerr]

@Greg Ducato

 

[Blue85]

Could be the throttle valve hanging up. This problem does tend to go away as the trans warms. Might be cured by giving the TV cable some quick tugs, or by tapping the gas pedal with the engine off. Could also be a stripped governor gear, making the transmission think you're still going slow. Seems less likely, but it's easy to pull the governor out to have a look.

The piece on the right is the heart of the throttle valve and it has no spring to return it (hydraulic pressure pushes it left), so a bit of junk can make it hang up. This makes the transmission behave like you're giving it more throttle than you really are.

 

[tRustyK5]

I'd say TV cable related, but obviously @Greg Ducato is the real expert here.

 

[Greg Ducato]

I'm guessing hung tv valve or misadjusted tv cable, Blue85's advice is excellent

 

[Lov-2-Rev]

Thank you gents for the replies and info. I will further investigate the TV cable and throttle valve. The fact that it won't shift gears manually kinda had me stumped. I didn't think that would be TV related.

 

[Lov-2-Rev]

Thanks again for the insight guys. Looks like the throttle valve was hanging up. Gave the cable a couple of tugs as suggested and it freed right up.

 

[Lov-2-Rev]

Now I just need to find a 73-75 thats being parted out. There are a few odds and ends I need to complete my full top conversion.