Clutch problem: gears clash when I down shift to first - The 1947 - Present Chevrolet & GMC Truck Message Board Network

grandpastruck · 02-21-2003, 01:39 AM

The gears clash badly on my 67 chevy inline 6 if I try to downshift from second to first without coming pretty much to a dead stop.

I trimmed the clutch pedal stop bumper and adjusted the clutch pedal free play to 3/4 of an inch, to no effect.

What would you suggest I try next?

Hooter · 02-21-2003, 01:45 AM

ydo u have a 4 speed with granny gear?
those tranny dont have synchros in first gear, so it wont go into gear unless you come to a complete stop, nothing is broken or wrong, thats just the way it is

mikep · 02-21-2003, 01:46 AM

I assume you have a 3 speed. I'm not too hip on those but I know on the truck 4 speeds I have had that 1st gear was non syncronized and shifting into first while moving wasnt an option. Somebody with more knowledge of 3 speeds might be more able to help but I think your trying to do something thats not really possible.

Hooter · 02-21-2003, 01:47 AM

hey what kind of truck do you have and where are you from?
and welcome from British Columbia

crazy longhorn · 02-21-2003, 01:57 AM

some of the 3spds werent full syncro either. The saginaw 3 spd was a full syncro(identified by a 7 bolt side cover), but the old muncie 3spd was not syncro in 1st gear. If memory is with me that one had 4 bolts on the side cover, & that may be what you have in the 67. You can shift em down tho......put it in neutral & let the clutch up, then rev the eng a couple times, then push the clutch down & shift it down......be careful tho, if you miss on the rpms, it will make a mess out of that box! crazyL

grandpastruck · 02-21-2003, 02:04 AM

Thanks for the quick answers!

So, no synchro? I need to practice my rolling stops from second gear then.

It's a c10 step-side with 3 on the tree. It belonged to my late grandfather and I'm trying to fix it up. Since I've never worked on a truck (or car) before, I spend a lot of time reading the shop manual.

I've managed to get it past emissions and to free up the doors and windows and get the lights working. Next up:

leaking brake fluid
6 miles to the gallon
a hissing at the front of the engine (blown gasket?)

Still, it's a great truck.

rusty ol' 69' · 02-21-2003, 02:16 AM

Sounds like you need to double clutch it. In other words, put the clutch in take it out of 2nd, and take the clutch off, depress the clutch again and throw it in 1st. If this don't work nothing will.

sneakysnake · 02-21-2003, 01:59 PM

you might pull the side plate off and look in there. I had one that
would grind if you didnt shift real slow, took it apart the brass syncromesh gears were eat up!

Blazer1970 · 02-21-2003, 02:15 PM

As others have said, if your tranny ever had 1st gear synchro (it probably didn't), it is worn out. If that is the case, it could be fixed. Otherwise, learn to double clutch. On a downshift, do it like crazy longhorn says:

release clutch
shift to neutral
engage clutch
blip the throttle to speed up the tranny input shaft a little
release the clutch again
shift to 1st

You will have to practice a little to learn how much throttle to give it to get the gears to mesh smoothly, but once you master it, it will become 2nd nature. It's cool because anyone riding with you will wonder what the hell you are doing. Before they invented synchromesh trannies, everyone had to know how to double clutch, or they were grindin' gears all the time. I would bet that tranny shops did a good business replacing gears in those days.

When I got my Blazer, it had a 3 speed with a bad 3rd gear synchro. I had to learn to double clutch to upshift into 3rd, and it took me a while to get out of the habit of doing it after I replaced the tranny.

crazy longhorn · 02-21-2003, 04:11 PM

Blazer 70.....cool

....another member of the double "clutch club"! if you play long enough , you can shift em up or down without the clutch(I would probably crash the hell out of the box now!)......been driving autos too long

basically what you are doing is matching speed on gears.......rev it to downshift

02-21-2003, 01:39 AM	#1
grandpastruck Registered User Join Date: Feb 2003 Posts: 4	Clutch problem: gears clash when I down shift to first The gears clash badly on my 67 chevy inline 6 if I try to downshift from second to first without coming pretty much to a dead stop. I trimmed the clutch pedal stop bumper and adjusted the clutch pedal free play to 3/4 of an inch, to no effect. What would you suggest I try next? __________________ Carlos

02-21-2003, 01:45 AM	#2
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	ydo u have a 4 speed with granny gear? those tranny dont have synchros in first gear, so it wont go into gear unless you come to a complete stop, nothing is broken or wrong, thats just the way it is __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

02-21-2003, 01:46 AM	#3
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	I assume you have a 3 speed. I'm not too hip on those but I know on the truck 4 speeds I have had that 1st gear was non syncronized and shifting into first while moving wasnt an option. Somebody with more knowledge of 3 speeds might be more able to help but I think your trying to do something thats not really possible. __________________ No truck :-(

02-21-2003, 01:47 AM	#4
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	hey what kind of truck do you have and where are you from? and welcome from British Columbia __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

02-21-2003, 01:57 AM	#5
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	some of the 3spds werent full syncro either. The saginaw 3 spd was a full syncro(identified by a 7 bolt side cover), but the old muncie 3spd was not syncro in 1st gear. If memory is with me that one had 4 bolts on the side cover, & that may be what you have in the 67. You can shift em down tho......put it in neutral & let the clutch up, then rev the eng a couple times, then push the clutch down & shift it down......be careful tho, if you miss on the rpms, it will make a mess out of that box! crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

02-21-2003, 02:04 AM	#6
grandpastruck Registered User Join Date: Feb 2003 Posts: 4	Thanks for the quick answers! So, no synchro? I need to practice my rolling stops from second gear then. It's a c10 step-side with 3 on the tree. It belonged to my late grandfather and I'm trying to fix it up. Since I've never worked on a truck (or car) before, I spend a lot of time reading the shop manual. I've managed to get it past emissions and to free up the doors and windows and get the lights working. Next up: leaking brake fluid 6 miles to the gallon a hissing at the front of the engine (blown gasket?) Still, it's a great truck. __________________ Carlos

02-21-2003, 02:16 AM	#7
rusty ol' 69' Grubbin' Join Date: Aug 2002 Location: Chico, CA Posts: 293	Double da clutch mang Sounds like you need to double clutch it. In other words, put the clutch in take it out of 2nd, and take the clutch off, depress the clutch again and throw it in 1st. If this don't work nothing will. __________________ project rust attack 1969 Chevrolet LWB w/ 307. I got power steering now woohooooo!!!!!!!

02-21-2003, 01:59 PM	#8
sneakysnake It's a catastrophic success. Join Date: Jan 2003 Location: Oklahoma Posts: 2,077	you might pull the side plate off and look in there. I had one that would grind if you didnt shift real slow, took it apart the brass syncromesh gears were eat up!

02-21-2003, 02:15 PM	#9
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	As others have said, if your tranny ever had 1st gear synchro (it probably didn't), it is worn out. If that is the case, it could be fixed. Otherwise, learn to double clutch. On a downshift, do it like crazy longhorn says: release clutch shift to neutral engage clutch blip the throttle to speed up the tranny input shaft a little release the clutch again shift to 1st You will have to practice a little to learn how much throttle to give it to get the gears to mesh smoothly, but once you master it, it will become 2nd nature. It's cool because anyone riding with you will wonder what the hell you are doing. Before they invented synchromesh trannies, everyone had to know how to double clutch, or they were grindin' gears all the time. I would bet that tranny shops did a good business replacing gears in those days. When I got my Blazer, it had a 3 speed with a bad 3rd gear synchro. I had to learn to double clutch to upshift into 3rd, and it took me a while to get out of the habit of doing it after I replaced the tranny. __________________ Tim

02-21-2003, 04:11 PM	#10
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Blazer 70.....cool ....another member of the double "clutch club"! if you play long enough , you can shift em up or down without the clutch(I would probably crash the hell out of the box now!)......been driving autos too long basically what you are doing is matching speed on gears.......rev it to downshift __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....



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