th350 trans...what can it be?

[kurtwas]

I've got an 86 Silverado 4x4 with a older driveline. The tag on the transfer case 1979, so I'm assuming that's the model year or motor, trans also.

Here's my issue, the trans is a th350. It will shift R, 1,2. It's not a firm shift 1-2, but it will shift, but won't hit 3 while on throttle. While driving if you bring it up to speed in 2nd, where it should shift to 3rd and then let off the gas, it will shift 3rd. As soon as you hit the gas slightly it'll "kick down" back to 2nd. I verified this by running up to 50 mph in D, letting off the gas and then manually down shifting to 2nd. I can manually down shift 3,2,1.

The kick down was be my 1st thought...but, I pulled the pan today replaced filter and fluid and vac mod. I wanted to look at he kick down cable in the trans, The kick cable is too long and not actuating the plunger in the trans. What else could be causing the trans to not stay in 3rd? Thanks!

 

[foamypirate]

Could be a stuck governor, perhaps.

Our local transmission/engine guru should have more input. @HotRodPC

 

[HotRodPC]

If it was a stuck governor, then it would be a late **** to 2nd also. I'd ask if it's shifting late to 2nd too, but pretty sure he's more deeper issues than that. As I was reading I was thinking kinked Detent cable holding the detent plunger. And I think it still might be that even though you've checked it. So here's the deal and what I'm thinking. The reason you THINK the detent cable isn't long enough and it's not actuating the detent plunger... is because the detent plunger is stuck IN and activated. Kinda like if your throttle on your carb was stuck hung open, you'd think your gas pedal cable was to long.

That's best case scenario. If it's not that, then my next guess is, when you THINK it's acatually in 3rd gear, it's not and you're actually just free wheeling in 2nd gear, the second you hit the gas, you're going back into 2nd. If that's the case, you've got broken hard parts in the transmisison. 2nd is offering NO engine braking and you're not getting into 3rd, making me think you might have a broken roller clutch gear that activates the intermediate clutch pack. Can't say for sure without looking at a diagnostic flow chart.

 

[kurtwas]

When I took the pan off I could see the plunger to actuate the trans kick down was not depressed. I took the filter off actuated the plunger manually and did get some trans fluid running out of a port. With the trans pan off I had my son press the gas pedal and the cable is at least .250 from actuating the plunger.

As for shifting to 3rd, when you let off the gas in D, at 50-55 mph, the tach drops and sounds like it "slid" into 3rd. If you lightly hit the gas on a flat surface the truck holds mph, rpm stays low. Also if you hit 50-55 and let it coast, in D, manually shift to 2nd, you can feel it down shift. it'll down shift manually to 1st also.

There is no slipping in R. with 35" tires in low/lock with no front drive shaft it'll smoke the tires. I know Low helps...a lot but the is no slipping?