Need help with tranny education - The 1947 - Present Chevrolet & GMC Truck Message Board Network

8door · 01-27-2005, 08:48 PM

I crawled under my truck today and dicovered a tube sticking out of bell housing on top passenger side.
Nothing hooked to it. Looks like a vacum hose should be connede as there is a loose one hanging down net to the tube.
What is it??????
The trans is a 350turbo tha engine is a 350 bilt in mid 1970.
I attached two pictures to help see what I asking.
Also I read you guys talking about TV throttle valve connection from carb. Mine has nothing other than the shift linkage.

What is missing??

Dean23 · 01-27-2005, 09:17 PM

Its just a vent hole. you can put a short piece of rubber hose on it to let it hang down slightly farther. I think its 5/16 hose will work

da-burb · 01-27-2005, 09:27 PM

I think you have a TH400 there. The vacuum modulator on a th350 is at the back of the trans.

And that is just a vent. You don't need to worry about it. It doesn't make a mess or cause any problems unless you over fill the trans.

Further identification is to look at the tranny pan. If it looks like the state of Illinois it is a th400. If it is a square with one corner clipped you have a th350.

krue · 01-27-2005, 09:37 PM

Quote:

Originally Posted by da-burb

I think you have a TH400 there. The vacuum modulator on a th350 is at the back of the trans.

And that is just a vent. You don't need to worry about it. It doesn't make a mess or cause any problems unless you over fill the trans.

Further identification is to look at the tranny pan. If it looks like the state of Illinois it is a th400. If it is a square with one corner clipped you have a th350.

Not to mention I don't see the kick down cable that goes right in front of the dipstick tube. Doesn't look like my TH350.

8door · 01-27-2005, 11:43 PM

Thanks guys, but the pan on mine is square with a corner clipped. The modulater is on the side next to dip stick tube( see pic) No cable anywere. I did notice a small hole with what looks like a threaded hole for a set screw.But the hole is about 1/2 "in diameter.
Hummmmm!!

Tx Firefighter · 01-28-2005, 08:10 AM

I'm with these guys on this deal. That modulator up on the side, by the cooler lines suggests a TH400.

The TH350 modulator is further back and points towards the rear of the truck rather than straight out the right side like yours does.

68w/sbc406 · 01-28-2005, 10:23 AM

.........

8door · 01-28-2005, 01:31 PM

Well here is proof this board really works. It got me out in the rain, yes it rains in Southern California,and looked at trans pan again.
It is a TH400.thanks 68W for the Tannyguide.Pictures are worth a thousand words.
Da Burb said the pan looks like Illinois, well I was getting ready to get out the USA map, but I thought no I saw the clipped edge.........well know I know.
So what next where and how should the kick down TV hook up go?
I only drove this truck a little and runs fine, but did not push it untill know more.

Bob Moore · 01-28-2005, 02:57 PM

The T400 has an electric kickdown. On the 67-70 cabs it is mounted on the carb with a pink wire from the fuse block(hot in run) and an orange wire to the trans connector on the drivers side toward the back. The switch is a plunger with a rubber boot. There is an ear that mounts on the carb throttle shaft arm that activates the kickdown when you punch it. The 71/72 models with throttle cable mount the switch in the cab by the gas petal. The wires are the same color.

The 67/70 switch and mounting bracket are quite common.
The factory wires often get very brittle from heat over the engine and oily running down to the trans.
The carb mounted ear is VERY hard to find.

The 71/72 switch carried over to 73 and is readily available.
The bracket it mounts to is hard to find.
The same problems exist for the orange wire in 71/72.

Hope this helps - Bob

8door · 01-28-2005, 03:18 PM

Bob Moore. Thanks for reply. I have read alot of articles since I found it is TH400.
My truck is a 68 with a later 350 engine and a Qjet carb, so I will be adding the kick down devices.
I am assuming this trans not stock for the 68 unless the original engine was a BB. so it may not have the correct wiring. I'll let you all know how it turns out.I don't have the build sheet nor glove box door sheet so not sure what truck came with.

Tx Firefighter · 01-28-2005, 06:01 PM

If you're not concerned with stockness and don't feel like scouring the world for correct parts, Lokar makes a real nice kickdown kit. It uses a cable that mounts to the carb and an electric box that connects to the transmission.

I used it on my last TH400 truck and was very pleased with the results and quality.

01-27-2005, 08:48 PM	#1
8door Not too old to learn Join Date: Mar 2004 Location: SoCal Posts: 617	Need help with tranny education I crawled under my truck today and dicovered a tube sticking out of bell housing on top passenger side. Nothing hooked to it. Looks like a vacum hose should be connede as there is a loose one hanging down net to the tube. What is it?????? The trans is a 350turbo tha engine is a 350 bilt in mid 1970. I attached two pictures to help see what I asking. Also I read you guys talking about TV throttle valve connection from carb. Mine has nothing other than the shift linkage. What is missing?? Attached Images __________________ 1968 C10 a way to long restoration.

01-27-2005, 09:17 PM	#2
Dean23 68cst_ss490 Join Date: May 2001 Location: edmonton,canada Posts: 1,363	Its just a vent hole. you can put a short piece of rubber hose on it to let it hang down slightly farther. I think its 5/16 hose will work __________________ Dean edmonton,canada a winter wonderland 2005 Chevrolet Avalanche LT cold air intake, performance exhaust, Comp cams cam, jba shorty ceramic headers. http://www.cardomain.com/ride/3090973

01-27-2005, 09:27 PM	#3
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	I think you have a TH400 there. The vacuum modulator on a th350 is at the back of the trans. And that is just a vent. You don't need to worry about it. It doesn't make a mess or cause any problems unless you over fill the trans. Further identification is to look at the tranny pan. If it looks like the state of Illinois it is a th400. If it is a square with one corner clipped you have a th350. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087 Last edited by da-burb; 01-27-2005 at 09:29 PM.

01-27-2005, 11:43 PM	#5
8door Not too old to learn Join Date: Mar 2004 Location: SoCal Posts: 617	Thanks guys, but the pan on mine is square with a corner clipped. The modulater is on the side next to dip stick tube( see pic) No cable anywere. I did notice a small hole with what looks like a threaded hole for a set screw.But the hole is about 1/2 "in diameter. Hummmmm!! __________________ 1968 C10 a way to long restoration.

01-28-2005, 08:10 AM	#6
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	I'm with these guys on this deal. That modulator up on the side, by the cooler lines suggests a TH400. The TH350 modulator is further back and points towards the rear of the truck rather than straight out the right side like yours does. __________________ I'm on the Instagram- @Gearhead_Kevin

01-28-2005, 01:31 PM	#8
8door Not too old to learn Join Date: Mar 2004 Location: SoCal Posts: 617	Well here is proof this board really works. It got me out in the rain, yes it rains in Southern California,and looked at trans pan again. It is a TH400.thanks 68W for the Tannyguide.Pictures are worth a thousand words. Da Burb said the pan looks like Illinois, well I was getting ready to get out the USA map, but I thought no I saw the clipped edge.........well know I know. So what next where and how should the kick down TV hook up go? I only drove this truck a little and runs fine, but did not push it untill know more. __________________ 1968 C10 a way to long restoration.

01-28-2005, 02:57 PM	#9
Bob Moore Registered User Join Date: Feb 2004 Location: Tacoma WA Posts: 1,365	Kick down The T400 has an electric kickdown. On the 67-70 cabs it is mounted on the carb with a pink wire from the fuse block(hot in run) and an orange wire to the trans connector on the drivers side toward the back. The switch is a plunger with a rubber boot. There is an ear that mounts on the carb throttle shaft arm that activates the kickdown when you punch it. The 71/72 models with throttle cable mount the switch in the cab by the gas petal. The wires are the same color. The 67/70 switch and mounting bracket are quite common. The factory wires often get very brittle from heat over the engine and oily running down to the trans. The carb mounted ear is VERY hard to find. The 71/72 switch carried over to 73 and is readily available. The bracket it mounts to is hard to find. The same problems exist for the orange wire in 71/72. Hope this helps - Bob __________________ 67 C-20 LWB, tilt, speed alert, vac, 454, T400 67 C-10 SWB, factory air with more to follow

01-28-2005, 03:18 PM	#10
8door Not too old to learn Join Date: Mar 2004 Location: SoCal Posts: 617	Bob Moore. Thanks for reply. I have read alot of articles since I found it is TH400. My truck is a 68 with a later 350 engine and a Qjet carb, so I will be adding the kick down devices. I am assuming this trans not stock for the 68 unless the original engine was a BB. so it may not have the correct wiring. I'll let you all know how it turns out.I don't have the build sheet nor glove box door sheet so not sure what truck came with. __________________ 1968 C10 a way to long restoration.

01-28-2005, 06:01 PM	#11
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	If you're not concerned with stockness and don't feel like scouring the world for correct parts, Lokar makes a real nice kickdown kit. It uses a cable that mounts to the carb and an electric box that connects to the transmission. I used it on my last TH400 truck and was very pleased with the results and quality. __________________ I'm on the Instagram- @Gearhead_Kevin



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