won't go into Drive? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

purple gas · 05-21-2006, 09:39 AM

Like it says. I can shift the lever into D, but the tranny won't shift. T-350, it is. Should I swap it out for another one? Could it be a simple thing? Should I hit it with a hammer? Are any carb linkage or vacume lines involved? Could it be a pull the pan and check / change something simple? Does it have anything to do with the fact for 1 revolution of a tire, the drive shaft rotates not quite exactly 2 times? Any advice would be greatly appreciated. FINALLY bombing around in my truck is fun, but avoiding the freeways sucks!

Karl Hoh · 05-21-2006, 10:50 AM

Have you checked oil level, linkage connections. Does it go into reverse? If yes then the clutch pac seal failed. If no, then the pump may have failed. Either way it needs to come out and rebuilt/replaced.

woodridge · 05-21-2006, 12:06 PM

Probably will have to come out, what does it do if you pull the shifter to low? If it pulls out and then will shift up you may have a bad low roller clutch, if it still won't move there is a problem with the forward clutch.

**pound41** · 05-21-2006, 01:13 PM

Be you start yanking out the tranny. If it worked fine before you need to check your modulator valve its on the the back and has a vacuum line on it. My 70 wouldn't go into drive. It had been sitting for a while I drove it. The next day no Drive. My Dad said change the modulator valve first. Cost less than $ 20. Switched it haven't had a problem since. Start simple

Longhorn Man · 05-21-2006, 01:20 PM

That doesn't make any sence..the mod valve only controls the RPM at which to upshift... nothing else. It'll go through all 3 gear (shifting at a MUCH higher RPM) with a bad mod valve.

purple gas · 05-22-2006, 09:06 AM

Thanks for the tips... Oil level is ok. It goes in reverse fine. You can shift manually from 1st to 2nd, but won't go into drive when the shifter goes there. Talked to guy who sold me the van I got the motor & trany from yesturday. He said it shifted fine, but it had sat for long time before I got it. When I first drove it ( and I still haven't driven it much ) it would rev pretty high before shifting out of 1st, and my liscenced mechanic buddy tweeked some linkage or something at the back of the motor and that helped the 1st-2nd thing. I'm thinkin I'll be yarding it out for a re-build anyways.

woodridge · 05-22-2006, 10:00 AM

Now with more info try this.
1. Make sure you have vacume at modulator valve.
The mod valve uses engine vacume to control shift timing and quality
2. Make sure T.V. (passing gear) cable is not hung in the pulled out position.
3. If #1 and #2 are not in spec and trans will not shift after they are corrected problem is most likely internal.

da-burb · 05-22-2006, 05:06 PM

Modulator valve...the fact that you have 1rst and 2nd gears but doesn't shift into 3rd is a bad modulator or the vacuum hose is off.

Longhorn Man · 05-22-2006, 05:50 PM

With the added info here, I will say mod valve.
You should be able to get 3rd amnually too. Get it up to about 50 in second (onless that's spinnin the snot out of it then do this at 40 - 45) and manually go from 2nd to 3rd... it'll probably go.
Check all the connections on the line going from the carb (or intake) to the modulator. There should be a hard line with short rubber hoses on either end.

05-21-2006, 12:06 PM	#3
woodridge Senior Member Join Date: Feb 2005 Location: Maynardville, Tn Posts: 3,030	Re: won't go into Drive? Probably will have to come out, what does it do if you pull the shifter to low? If it pulls out and then will shift up you may have a bad low roller clutch, if it still won't move there is a problem with the forward clutch. __________________ SEMA Network- Protect our Hobby! 71 C30 in pieces, starting to come together. Click here for A Place For Tennessee Truck Enthusiest To Meet

05-21-2006, 01:13 PM	#4
pound41 Registered User Join Date: Dec 2002 Location: Northern Virginia Posts: 1,269	Re: won't go into Drive? Be you start yanking out the tranny. If it worked fine before you need to check your modulator valve its on the the back and has a vacuum line on it. My 70 wouldn't go into drive. It had been sitting for a while I drove it. The next day no Drive. My Dad said change the modulator valve first. Cost less than $ 20. Switched it haven't had a problem since. Start simple

05-21-2006, 01:20 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: won't go into Drive? That doesn't make any sence..the mod valve only controls the RPM at which to upshift... nothing else. It'll go through all 3 gear (shifting at a MUCH higher RPM) with a bad mod valve.

05-22-2006, 09:06 AM	#6
purple gas Registered User Join Date: Oct 2004 Location: saskatoon, planet earth Posts: 686	Re: won't go into Drive? Thanks for the tips... Oil level is ok. It goes in reverse fine. You can shift manually from 1st to 2nd, but won't go into drive when the shifter goes there. Talked to guy who sold me the van I got the motor & trany from yesturday. He said it shifted fine, but it had sat for long time before I got it. When I first drove it ( and I still haven't driven it much ) it would rev pretty high before shifting out of 1st, and my liscenced mechanic buddy tweeked some linkage or something at the back of the motor and that helped the 1st-2nd thing. I'm thinkin I'll be yarding it out for a re-build anyways. __________________ I got a bench seat baby, you don't have to sit over there.

05-22-2006, 10:00 AM	#7
woodridge Senior Member Join Date: Feb 2005 Location: Maynardville, Tn Posts: 3,030	Re: won't go into Drive? Now with more info try this. 1. Make sure you have vacume at modulator valve. The mod valve uses engine vacume to control shift timing and quality 2. Make sure T.V. (passing gear) cable is not hung in the pulled out position. 3. If #1 and #2 are not in spec and trans will not shift after they are corrected problem is most likely internal. __________________ SEMA Network- Protect our Hobby! 71 C30 in pieces, starting to come together. Click here for A Place For Tennessee Truck Enthusiest To Meet

05-21-2006, 09:39 AM	#1
purple gas Registered User Join Date: Oct 2004 Location: saskatoon, planet earth Posts: 686	won't go into Drive? Like it says. I can shift the lever into D, but the tranny won't shift. T-350, it is. Should I swap it out for another one? Could it be a simple thing? Should I hit it with a hammer? Are any carb linkage or vacume lines involved? Could it be a pull the pan and check / change something simple? Does it have anything to do with the fact for 1 revolution of a tire, the drive shaft rotates not quite exactly 2 times? Any advice would be greatly appreciated. FINALLY bombing around in my truck is fun, but avoiding the freeways sucks! __________________ I got a bench seat baby, you don't have to sit over there.

05-21-2006, 10:50 AM	#2
Karl Hoh A little east of nowhere Join Date: Feb 2006 Location: LaBroquerie,Manitoba Canada Posts: 168	Re: won't go into Drive? Have you checked oil level, linkage connections. Does it go into reverse? If yes then the clutch pac seal failed. If no, then the pump may have failed. Either way it needs to come out and rebuilt/replaced. __________________ 68 C10 250 4spd 69 C20 327 4spd 69 910 250 3spd 80 K10 350 4spd 76 C60 366 5spd school bus "THERE'S NOTHING YOU CAN BREAK THAT SOMEONE CAN'T BE PAID TO REPAIR"

05-22-2006, 05:06 PM	#8
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	Re: won't go into Drive? Modulator valve...the fact that you have 1rst and 2nd gears but doesn't shift into 3rd is a bad modulator or the vacuum hose is off. __________________ 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

05-22-2006, 05:50 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: won't go into Drive? With the added info here, I will say mod valve. You should be able to get 3rd amnually too. Get it up to about 50 in second (onless that's spinnin the snot out of it then do this at 40 - 45) and manually go from 2nd to 3rd... it'll probably go. Check all the connections on the line going from the carb (or intake) to the modulator. There should be a hard line with short rubber hoses on either end.



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