What I learned last week - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tynee · 04-24-2006, 05:20 PM

So, I was complaining to a guy at work about how I was driving my buddy's Jimmy when the 307 started running rough, then while I was trying to trouble-shoot that, the th350 quit shifting. Without even hesitating, he said, "You've got a vacuum line to the modulator valve leaking."

The more I thought about it, the more sense it made. It explained the miss-fire, the transmission issue, and the power brake issue that I hadn't even thought about yet all in one fell swoop.

I was reminded of a couple of things:
1) There is really no substitute for experience. I've never had a vacuum leak cause a transmission to quit shifting, I didn't even know anything about a modulator valve, much less how it worked.
2) Sometimes, it just takes sombody else who is removed from the situation to look at it objectively.
3) A '71 Jimmy is a REALLY fun truck to drive.

I went home, fired it up and followed my ear to the GAPING vacuum leak (it was hard to hear over the exhaust unless you were listening for a vacuum leak), and cured all the problems in two minutes with a grand total of zero dollars invested in the repair.

*Medicanman71* · 04-24-2006, 06:52 PM

awsome!

LUV2XCLR8 · 04-24-2006, 07:00 PM

vtblazer · 04-24-2006, 07:07 PM

Heh heh, go figure.

chevy_fatman · 04-24-2006, 07:36 PM

Pop's72 · 04-24-2006, 09:33 PM

_Dick_ · 04-24-2006, 10:23 PM

Great Story There are some awsome minds on this board

krue · 04-24-2006, 10:56 PM

That one has bitten me a few times. If the tranny quits shifting, but you can shift it manually that's the first thing to check. I thought my tranny was toast 'cuz I was snatching some logs around in my woods when it quit shifting. I finally decided to look under the hood and found the vacuum line off.

k-nuts · 04-25-2006, 11:04 PM

Good job on that one.

My grandfather's car had been sitting for a year or so. When he passed away we moved it out of the garage and it wouldn't shift out of low even manually. I decided take it to my place to get it going again. I stopped off at the first gas station filled the trans fluid to the hot mark (it was HOT driving in low!)

Problem fixed.

Anyone need a clean '93 New Yorker????? Shifts great!

04-24-2006, 05:20 PM	#1
Tynee I miss this truck. Join Date: Dec 2001 Location: Lexington, KY U.S.A. Posts: 2,863	What I learned last week So, I was complaining to a guy at work about how I was driving my buddy's Jimmy when the 307 started running rough, then while I was trying to trouble-shoot that, the th350 quit shifting. Without even hesitating, he said, "You've got a vacuum line to the modulator valve leaking." The more I thought about it, the more sense it made. It explained the miss-fire, the transmission issue, and the power brake issue that I hadn't even thought about yet all in one fell swoop. I was reminded of a couple of things: 1) There is really no substitute for experience. I've never had a vacuum leak cause a transmission to quit shifting, I didn't even know anything about a modulator valve, much less how it worked. 2) Sometimes, it just takes sombody else who is removed from the situation to look at it objectively. 3) A '71 Jimmy is a REALLY fun truck to drive. I went home, fired it up and followed my ear to the GAPING vacuum leak (it was hard to hear over the exhaust unless you were listening for a vacuum leak), and cured all the problems in two minutes with a grand total of zero dollars invested in the repair. __________________ '07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT.

04-24-2006, 06:52 PM	#2
Medicanman71 Account Suspended Join Date: May 2005 Location: Where the Wild Things Are Posts: 696	Re: What I learned last week awsome!

04-24-2006, 07:00 PM	#3
LUV2XCLR8 The LuvShack Garage Join Date: Jan 2004 Location: Maple Grove, TN (West Side) Posts: 30,475	Re: What I learned last week __________________ Owner/Op: "TN Classic Transport Carriers" The Toy: "Square Vette" 72 Hybrid Blazer Toy Barn: "LuvShack" 40 x 60 x 20 Shop Big Piggy: "Goliath" 07 Kodiak C4500 Lil Piggy:"Maddy" 88 Silverado 3500 Hauler: "Feathers" 14 Aluma 8218T

04-24-2006, 07:07 PM	#4
vtblazer Registered User Join Date: Oct 2003 Location: Central Vermont Posts: 8,538	Re: What I learned last week Heh heh, go figure.

04-24-2006, 07:36 PM	#5
chevy_fatman Where's my beer? Join Date: Aug 2002 Location: I live in the state of denial.... Posts: 5,621	Re: What I learned last week __________________ Paul How do you make the invisible, visible?.........You take it away.

04-24-2006, 09:33 PM	#6
Pop's72 It's ok to stare... Join Date: Dec 2004 Location: San Jose, CA Posts: 669	Re: What I learned last week __________________ -Matt 1971 Blazer/Jimmy : Factory 2WD, Factory AC, Crate 350

04-24-2006, 10:23 PM	#7
_Dick_ PROUD TO BE A MEMBER Join Date: Sep 2005 Location: Jax Florida Posts: 234	Re: What I learned last week Great Story There are some awsome minds on this board

04-24-2006, 10:56 PM	#8
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: What I learned last week That one has bitten me a few times. If the tranny quits shifting, but you can shift it manually that's the first thing to check. I thought my tranny was toast 'cuz I was snatching some logs around in my woods when it quit shifting. I finally decided to look under the hood and found the vacuum line off. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

04-25-2006, 11:04 PM	#9
k-nuts Registered User Join Date: Feb 2006 Location: TX Posts: 252	Re: What I learned last week Good job on that one. My grandfather's car had been sitting for a year or so. When he passed away we moved it out of the garage and it wouldn't shift out of low even manually. I decided take it to my place to get it going again. I stopped off at the first gas station filled the trans fluid to the hot mark (it was HOT driving in low!) Problem fixed. Anyone need a clean '93 New Yorker????? Shifts great! Last edited by k-nuts; 04-25-2006 at 11:07 PM.



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