Tranny problems.. I think. Please help! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

71GeneralMotorsCorp · 05-31-2013, 08:49 PM

Hey guys well here is the story.. Today I was driving my truck home from work and I ran through a puddle. shortly after that I noticed my truck was acting up so I took a couple laps around the block to see.. The transmission would get to the top of 1st and would not shift into 2nd unless i let off and then got back on it and it would act like a "neutral drop".. and It refuses to shift into 3rd gear.. Now here is the weird part, the truck has a loud hissing noise coming from right under the cab, almost like a huge vacuum leak. ALSO, If I manually go from 1st to second using the column it will shift into second after a small delay, but when I put it into drive it does not shift into 3rd. Truck has a mild 350 with a turbo 350.

**68350** · 05-31-2013, 08:51 PM

Did the vacuum line come off the tranny? I may be wrong in thinking th350s have the vacuum line running from the intake to the tranny but I know th400s have one.
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67 chevelle · 05-31-2013, 09:07 PM

you ripped the rubber hose off of the vacuum modulator

**TBONE1964** · 05-31-2013, 10:33 PM

I agree with all of the above. Simple fix.

Toxic Orange · 05-31-2013, 11:13 PM

Yep, yep, yep. I took mine out of a drive tonight after doing some vacuum line rerouting recently and it was doing the same thing. I had accidentally knocked off the rubber line at the modulator. Plugged it back on and it was good as new.

71GeneralMotorsCorp · 06-01-2013, 12:04 AM

okay, I'm gonna mess with it tomorrow.. would that vacuum line also cause some major misfiring?

Toxic Orange · 06-01-2013, 12:21 AM

It would cause a vacuum leak so it could cause less than desirable running conditions. Hook up the line, test drive and go from there.

tmc1986 · 06-01-2013, 12:49 AM

I had a turbo400/350ci in a jeep one time. I ripped a hose on the tranny and ended up taking on a ton of water in and burned it up. As long as you didn't submerge that thing you shouldn't have done any kind of serious damage. Good luck
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Henry50 · 06-01-2013, 12:58 AM

Quote:

Originally Posted by 71GeneralMotorsCorp

okay, I'm gonna mess with it tomorrow.. would that vacuum line also cause some major misfiring?

Yep, It will run pretty bad with the vacuum line to trans pulled off, and it won't shift.

05-31-2013, 08:49 PM	#1
71GeneralMotorsCorp Registered User Join Date: Jul 2011 Location: Kansas Posts: 266	Tranny problems.. I think. Please help! Hey guys well here is the story.. Today I was driving my truck home from work and I ran through a puddle. shortly after that I noticed my truck was acting up so I took a couple laps around the block to see.. The transmission would get to the top of 1st and would not shift into 2nd unless i let off and then got back on it and it would act like a "neutral drop".. and It refuses to shift into 3rd gear.. Now here is the weird part, the truck has a loud hissing noise coming from right under the cab, almost like a huge vacuum leak. ALSO, If I manually go from 1st to second using the column it will shift into second after a small delay, but when I put it into drive it does not shift into 3rd. Truck has a mild 350 with a turbo 350. __________________ "Repetition penetrates even the dullest of minds"

05-31-2013, 08:51 PM	#2
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Re: Tranny problems.. I think. Please help! Did the vacuum line come off the tranny? I may be wrong in thinking th350s have the vacuum line running from the intake to the tranny but I know th400s have one. Posted via Mobile Device __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

05-31-2013, 09:07 PM	#3
67 chevelle Registered User Join Date: May 2013 Location: WEST PALM FLORIDA Posts: 1,174	Re: Tranny problems.. I think. Please help! you ripped the rubber hose off of the vacuum modulator

05-31-2013, 10:33 PM	#4
TBONE1964 Cluster King Join Date: Nov 2012 Location: Junction City, OR Posts: 5,263	Re: Tranny problems.. I think. Please help! I agree with all of the above. Simple fix.

05-31-2013, 11:13 PM	#5
Toxic Orange Registered User Join Date: Apr 2013 Location: Flower Mound TX Posts: 173	Re: Tranny problems.. I think. Please help! Yep, yep, yep. I took mine out of a drive tonight after doing some vacuum line rerouting recently and it was doing the same thing. I had accidentally knocked off the rubber line at the modulator. Plugged it back on and it was good as new.

06-01-2013, 12:04 AM	#6
71GeneralMotorsCorp Registered User Join Date: Jul 2011 Location: Kansas Posts: 266	Re: Tranny problems.. I think. Please help! okay, I'm gonna mess with it tomorrow.. would that vacuum line also cause some major misfiring? __________________ "Repetition penetrates even the dullest of minds"

06-01-2013, 12:21 AM	#7
Toxic Orange Registered User Join Date: Apr 2013 Location: Flower Mound TX Posts: 173	Re: Tranny problems.. I think. Please help! It would cause a vacuum leak so it could cause less than desirable running conditions. Hook up the line, test drive and go from there.

06-01-2013, 12:49 AM	#8
tmc1986 Registered User Join Date: Apr 2013 Location: enumclaw, wa Posts: 143	Re: Tranny problems.. I think. Please help! I had a turbo400/350ci in a jeep one time. I ripped a hose on the tranny and ended up taking on a ton of water in and burned it up. As long as you didn't submerge that thing you shouldn't have done any kind of serious damage. Good luck Posted via Mobile Device __________________ '67 2wd LWB 350/4speed.



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