Turbo 350 only shifts by hand? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

YourBuddy'sTruck · 05-26-2013, 07:15 PM

I managed to get my '70 C20 running and with lights and brakes and all the other fun stuff.
Maiden voyage had it not shifting gears at all unless I manually put it in 1st, then 2nd, and then Drive.
Fluid is full up to the mark?

I have to mention that the truck has not been run in 4-5 years.
Hot Rod guy sold it to Computor Guy, who then sold it to me in Non-Running condition.
In the process of shifting ownership, the C20 was very poorly painted a fancy bright yellow and the rear bumper removed. Then the entire interior was stripped for ?paint?
Totally a basket case in the cab. Wires everywhere with more splices that I care for, etc.
With all that, I've been questioniing everything that I come accross. (and my sanity too at times.)

Anway....any clues on the Turbo 350 would be appreciated.
So far, one guy said something about a shift kit that makes it need to be manually shifted? What's that about?
Only about 2-3 hours of run time on it so far and it is NOT a rebuild.
Thanks for any knowledge that comes my way.
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**TBONE1964** · 05-26-2013, 07:29 PM

Do you have vacuum to the vacuum modulator? It should be to manifold vacuum source usually behind the carb, then a steel line that runs down the passenger side of the trans to the modulator. You need this hooked up for correct shift points.

BTW, there is such a thing as a fully manual valve body which means what it says, no auto shift. It will only shift the trans manually. These are usually used in a drag race type of environment. If you have one in your trans then you will need to shift it manually or remove it for a stock valve body.

Check your vacuum to the modulator first.

YourBuddy'sTruck · 05-26-2013, 08:00 PM

Yes. Have great vacuum off manifold behind carb & right by HEI (switched out Distributor).

How would I identify this drag race mod?
Guessing not from the outside.

Seams to require manual downshift also.
Not upset if this is what I have, more worried if its a tranny on
the way out.
I bought the truck to HAUL for my bizz.

(And my hauling bizz is delivering LIQUOR to bars! Pallets Full Of The Stuff!)

So....I do Not want a breakdown on the road with $25-30K of "cargo" in the back!
Yep...she's my Rum Runner Truck. Cheers!
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HotRod C/10 · 05-26-2013, 08:04 PM

you sure its not the oil pressure port your in by the disributor?

luvbowties · 05-26-2013, 08:10 PM

Quote:

Originally Posted by YourBuddy'sTruck

Yes. Have great vacuum off manifold behind carb & right by HEI (switched out Distributor).

How would I identify this drag race mod?
Guessing not from the outside.

Seams to require manual downshift also.
Not upset if this is what I have, more worried if its a tranny on
the way out.
I bought the truck to HAUL for my bizz.

(And my hauling bizz is delivering LIQUOR to bars! Pallets Full Of The Stuff!)

So....I do Not want a breakdown on the road with $25-30K of "cargo" in the back!
Yep...she's my Rum Runner Truck. Cheers!
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You need to check for vacuum AT THE MODULATOR--not at the manifold/carb.
Sam

**TBONE1964** · 05-26-2013, 08:13 PM

Quote:

Originally Posted by YourBuddy'sTruck

Yes. Have great vacuum off manifold behind carb & right by HEI (switched out Distributor).

How would I identify this drag race mod?
Guessing not from the outside.

Seams to require manual downshift also.
Not upset if this is what I have, more worried if its a tranny on
the way out.
I bought the truck to HAUL for my bizz.

(And my hauling bizz is delivering LIQUOR to bars! Pallets Full Of The Stuff!)

So....I do Not want a breakdown on the road with $25-30K of "cargo" in the back!
Yep...she's my Rum Runner Truck. Cheers!
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If the person who built the trans, set it up for a manual valve body then they would have (should have) left the vacuum modulator out and put a plug in it's place. Do you have a vacuum modulator? It will be on the passenger side of the trans and have a vacuum hose connected to it from manifold vacuum source.

When you manually shift it, does it kick like a mule or is it a softer more user friendly shift? If it shifts OK manually and you are good with it, then use it as is. What does the trans fluid look like? Nice and pink and smell good?

YourBuddy'sTruck · 05-26-2013, 08:17 PM

Vacuum source is brass fitting with two nipples. One lined to Tranny, the other to a bolt tightly in to block the line.
The second line (blocked one) is so close to my HEI that I wish it was not there.

Who would put a "Race Mod Tranny" in a C20 with a stock 350?
(My engine is not original and I see where this may be headed!)
= (]
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**TBONE1964** · 05-26-2013, 08:24 PM

Quote:

Originally Posted by YourBuddy'sTruck

Vacuum source is brass fitting with two nipples. One lined to Tranny, the other to a bolt tightly in to block the line.
The second line (blocked one) is so close to my HEI that I wish it was not there.

Who would put a "Race Mod Tranny" in a C20 with a stock 350?
(My engine is not original and I see where this may be headed!)
= (]
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Can you post some photos and show area near distributor and one near vacuum modulator on trans. I want to see exactly what you are working with here.

**mr48chev** · 05-26-2013, 09:03 PM

The short hose that goes between the steel vacuum line and the modulator fails on a regular basis too. That happens even more on rigs with leaks like my daily had as seen in this photo.

Make sure that hose is in good shape and connected tightly on both ends. The diaphragm in the modulator may have failed too and you would usually have fluid leaking out of the vacuum tube on the modulator if that happens.

That's a smaller size aftermarket modulator, Most of the original ones were the larger size like this one that you can see on the right side of the extension housing on the original trans from the truck.

I had a governor fail on my trans once but I don't think that the truck went at all that time let alone shift manually.

If you aren't using the second leg of the vacuum T off the manifold you can remove that T and put in a 90 with the correct size tube to connect to the modulator line and get a bit more clearance.

YourBuddy'sTruck · 05-26-2013, 09:08 PM

oooh...this is good stuff!
I'll dig in more tomorrow if time permits.
Thanks!

PS. How do you post pics here? I've iStuff, pad, phone...hmmm. Much to learn...Much to learn.
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YourBuddy'sTruck · 05-26-2013, 09:10 PM

Quote:

Originally Posted by HotRod C/10

you sure its not the oil pressure port your in by the disributor?

Yes...Oil pressure and MPH are the only gauges that I actually have working!
Ha!
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YourBuddy'sTruck · 05-27-2013, 10:24 AM

Totally the vacuum line at the Modulator!
Must have pulled out when I was locking it and the dip stick down through tranny mounting bolt.
Thanks for the help!
I'm a moron with transmissions (among other kinds) and I really appreciate the knowledge base of you forum members.
You guys really know your stuff!
Posted via Mobile Device

05-26-2013, 07:15 PM	#1
YourBuddy'sTruck Registered User Join Date: May 2013 Location: Catawba Island, OH Posts: 203	Turbo 350 only shifts by hand? I managed to get my '70 C20 running and with lights and brakes and all the other fun stuff. Maiden voyage had it not shifting gears at all unless I manually put it in 1st, then 2nd, and then Drive. Fluid is full up to the mark? I have to mention that the truck has not been run in 4-5 years. Hot Rod guy sold it to Computor Guy, who then sold it to me in Non-Running condition. In the process of shifting ownership, the C20 was very poorly painted a fancy bright yellow and the rear bumper removed. Then the entire interior was stripped for ?paint? Totally a basket case in the cab. Wires everywhere with more splices that I care for, etc. With all that, I've been questioniing everything that I come accross. (and my sanity too at times.) Anway....any clues on the Turbo 350 would be appreciated. So far, one guy said something about a shift kit that makes it need to be manually shifted? What's that about? Only about 2-3 hours of run time on it so far and it is NOT a rebuild. Thanks for any knowledge that comes my way. Posted via Mobile Device Posted via Mobile Device

05-26-2013, 07:29 PM	#2
TBONE1964 Cluster King Join Date: Nov 2012 Location: Junction City, OR Posts: 5,263	Re: Turbo 350 only shifts by hand? Do you have vacuum to the vacuum modulator? It should be to manifold vacuum source usually behind the carb, then a steel line that runs down the passenger side of the trans to the modulator. You need this hooked up for correct shift points. BTW, there is such a thing as a fully manual valve body which means what it says, no auto shift. It will only shift the trans manually. These are usually used in a drag race type of environment. If you have one in your trans then you will need to shift it manually or remove it for a stock valve body. Check your vacuum to the modulator first.

05-26-2013, 08:00 PM	#3
YourBuddy'sTruck Registered User Join Date: May 2013 Location: Catawba Island, OH Posts: 203	Re: Turbo 350 only shifts by hand? Yes. Have great vacuum off manifold behind carb & right by HEI (switched out Distributor). How would I identify this drag race mod? Guessing not from the outside. Seams to require manual downshift also. Not upset if this is what I have, more worried if its a tranny on the way out. I bought the truck to HAUL for my bizz. (And my hauling bizz is delivering LIQUOR to bars! Pallets Full Of The Stuff!) So....I do Not want a breakdown on the road with $25-30K of "cargo" in the back! Yep...she's my Rum Runner Truck. Cheers! Posted via Mobile Device Posted via Mobile Device Posted via Mobile Device Posted via Mobile Device

05-26-2013, 08:04 PM	#4
HotRod C/10 Registered User Join Date: Feb 2012 Location: Albuquerque NM Posts: 3,053	Re: Turbo 350 only shifts by hand? you sure its not the oil pressure port your in by the disributor? __________________ SOLD -77 CHEYENNE SWB, LS SWAPPED -1976 SILVERADO YUBA GOLD/NEUTRAL (2-TONE)

05-26-2013, 08:17 PM	#7
YourBuddy'sTruck Registered User Join Date: May 2013 Location: Catawba Island, OH Posts: 203	Re: Turbo 350 only shifts by hand? Vacuum source is brass fitting with two nipples. One lined to Tranny, the other to a bolt tightly in to block the line. The second line (blocked one) is so close to my HEI that I wish it was not there. Who would put a "Race Mod Tranny" in a C20 with a stock 350? (My engine is not original and I see where this may be headed!) = (] Posted via Mobile Device

05-26-2013, 09:03 PM	#9
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,640	Re: Turbo 350 only shifts by hand? The short hose that goes between the steel vacuum line and the modulator fails on a regular basis too. That happens even more on rigs with leaks like my daily had as seen in this photo. Make sure that hose is in good shape and connected tightly on both ends. The diaphragm in the modulator may have failed too and you would usually have fluid leaking out of the vacuum tube on the modulator if that happens. That's a smaller size aftermarket modulator, Most of the original ones were the larger size like this one that you can see on the right side of the extension housing on the original trans from the truck. I had a governor fail on my trans once but I don't think that the truck went at all that time let alone shift manually. If you aren't using the second leg of the vacuum T off the manifold you can remove that T and put in a 90 with the correct size tube to connect to the modulator line and get a bit more clearance. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

05-26-2013, 09:08 PM	#10
YourBuddy'sTruck Registered User Join Date: May 2013 Location: Catawba Island, OH Posts: 203	Re: Turbo 350 only shifts by hand? oooh...this is good stuff! I'll dig in more tomorrow if time permits. Thanks! PS. How do you post pics here? I've iStuff, pad, phone...hmmm. Much to learn...Much to learn. Posted via Mobile Device

05-27-2013, 10:24 AM	#12
YourBuddy'sTruck Registered User Join Date: May 2013 Location: Catawba Island, OH Posts: 203	Re: Turbo 350 only shifts by hand? Totally the vacuum line at the Modulator! Must have pulled out when I was locking it and the dip stick down through tranny mounting bolt. Thanks for the help! I'm a moron with transmissions (among other kinds) and I really appreciate the knowledge base of you forum members. You guys really know your stuff! Posted via Mobile Device



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