Turbo 350 passing gear or more accurately wont pass...

[cmcclean]

So, Chevy 350 with quadrajet and turbo 350 combo. Will not engage passing gear.

Kickdown cable is set at end of throw at wide open throttle after choke has come off. Cable will retract about half the length of the groove at the carb connection if manually pulled and released.

I believe I have the cable adjusted correctly. The trans shifts perfectly in all other respects. Any thoughts? Is there a seperate adjustment? If the cable was disconnected in the trans body would it still retract? I do not know when the last time this was working properly as the PO did not have the kickdown hooked up.

[MusicMan70]

Do you feel tension on it when you release it? Maybe it became unhooked down where it bolts to the tranny.

[cmcclean]

Yes, I can feel some spring tension and when I let go it springs back about half way.
Posted via Mobile Device

[cmcclean]

I just went out to take a look (feel) that sounds wrong also, whatever. The connection to the carb is slotted, pulling on the cable it is free for the first 1/2 of the travel then spring loaded for the second half. Should it have spring tension for the full travel?
Posted via Mobile Device

[MusicMan70]

Post a pic if you can.
Is the transmission connected to full manifold vacuum and not off the carb? I would follow the cable down to where it bolts to the trans. It's only one bolt to loosen, and lift it slowly to see if it's properly threaded/hooked.

[cmcclean]

Yes, full manifold pressure.

I haven't figured out how to post pictures. It looks almost identical to the images posted by Rougheup72 in this thread http://67-72chevytrucks.com/vboard/s....php?p=1788409 except that it's a Quadrajet.

I think maybe the cable is disconnected in the trans but the return spring is still engaged. Is that possible? How is it hooked up in the trans?

[clinebarger]

Is the Detent cable tight at WOT?
The only time its pulled is near WOT, The slot, & not returning all the way is normal.
To be sure, Drop the pan & make sure the Detent Valve is pushed all the way while someone holds the throttle open. Seen alot of messed up Detent linkages.


At what RPM does WOT shifts happen? If below 3800 RPM.....It will NEVER Detent because the Governor pressure is to high from a worn or mismatched governor.

Remove governor, Measure the "Lands".....If below .797" Replace governor, New spec is .800". If that's OK, carry-on with some spring changes to get WOT shifts closer to 4500 RPM. http://www.tciauto.com/tc/gm-governo...ation-kit.html

[MusicMan70]

Here is the cable connection to the trans. When you unbolt it, the end should have an eyelet. I just used a bent paperclip to give you an idea what to look for. hope this helps.

[cmcclean]

Thanks guys,
Cable is tight at WOT.
I do not know the RPM for WOT shift points (no tach). I did run it through the gears today at WOT and it did seem to shift a little early but thats just a guess.

I did unbolt the cable housing and make sure it was connected inside and it was. Thanks for the pics.

It sounds like I need to drop the pan and make sure the detent valve is pushed all the way in. I'll do a search and see what it looks like from the pan side (unless somebody has a picture...).
If that looks correct I'll move onto the Governor.

This is what weekends are for right.

[Stepside Jim]

I don't know if this helps, but once the linkage is hooked to the cable as shown in the last picture, it goes in and connects to a pivoting bracket.

[cmcclean]

thanks,
I'm going to guess the detent valve is the plunger on the right hand side (in your picture) that looks like it would be pushed in when the linkage is pulled.

[Stepside Jim]

Yes, the picture is upside down. When you pull on your cable, you should feel like a two stage spring. I'm referring to as you pull the slotted end of the cable, you will feel a slight resistance, then as you pull the last 3/4", the spring tension may have a stiffer spring resistance.

If you feel both stages, you're pretty well working the full motion of the detent valve.

One item that could also give a problem is the modulator valve. If the transmission is shifting fine this may not be a problem.

On the other hand, the modulator valve reads the manifold using the vacuum line off the intake. As you push down the throttle which inturn pulls the detent cable, the manifold vacuum drops. The manifold vacuum loss is read by the vacuum modulator, this loss of vacuum tells the transmission that the engine is working under a load, meaning, it maybe time to down shift.

As you go under the vehicle, pull the vacuum line off the modulator valve, sometimes as it goes bad, the diaphram leaks and you'll have transmission fluid drip out of the vacuum line. This could be a quick check to see if the modulator valve might be giving you problems also.

Hope this helps... Jim

[clinebarger]

The Modulator doesnt effect WOT upshifts or downshifts, It effects Part Throttle upshifts & downshifts along with the Governor.

If the Detent cable is hooked up correctly, At WOT the Detent Valve blocks Modulator pressure from reaching the Shift Valves & allows Detent fluid to flow to the shift valves & try to put the Shift Valves in the "Downshift" state with more pressure than the Modulator. If Governor pressure is to high for the Detent pressure to overcome.....No Detent.

At WOT the Detent pressure effects all 3 downshift modes....2-1, 3-2 & 3-1.

Testing TH350 Detent...
From a standing start at steady very light throttle..........As Soon as it does a 2-3 shift........Floor it.......It should go back to 1st (3-1 detent).

[cmcclean]

I can't really feel any difference or detent when I pull but maybe I just don't have the touch.

I will try the light throttle into 3rd then WOT. I don't have much hope though as I have never had it downshift with throttle application.

I'll check it all but my gut tells me it is the governor. I'll keep you guys posted thanks for the help and suggestions. My knowledge of auto transmissions is pretty limited.
Posted via Mobile Device

[cableguy0]

Pull the pan and make sure the detent bracket that pushed the plunger in the valve body isnt in there backward. Also pop the side and yank the governor. It should move freely and the gear intact.

[cmcclean]

I have had other chore's so have not been able to pull the pan yet. I have been able to run the WOT test from light throttle.
From light throttle it changes to 3rd at about 20 mph. If i mash the throttle it will shift down to second gear only. It will downshift to second only between 20 to 30 mph. anything above that is does not downshift at all.
With that in mind could it be a bad modulator in conjunction with a governor that is mismatched or worn?

[clinebarger]

Originally Posted by cmcclean

Could it be a bad modulator in conjunction with a governor that is mismatched or worn?

Governor. If the Part Throttle shift are OK, Then so is the Modulator.

[cmcclean]

Thanks Clinebarger. I think I will get a new governor and the TCIkit and see if I can't get it dialed in.
Posted via Mobile Device