clutch won't disengage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HelpMyZ · 01-13-2007, 07:50 PM

ok, I've got an 87 gmc 1ton with the 4speed sm465 tranny and np205 t-case... I just put a smallblock 350 in it, and can't get the clutch to disengage... anyone have any clues what my problem may be? or what I should try?

jeffspower · 01-13-2007, 07:59 PM

What happens when you start it in gear with the clutch pedal all the way down? Does it creep, or lunge with no slippage?

I can't remember- is this '87 mech. clutch or hydraulic?

HelpMyZ · 01-13-2007, 08:00 PM

it's a hyd clutch.. I'm afraid to try and start it in gear... the battery is shot, so it's gotta be jump started... could get messy if it jumps.. haha

HelpMyZ · 01-13-2007, 08:36 PM

ok, it was in 1st, I just tapped the starter and it lunged forward

**68 Stepside** · 01-13-2007, 08:40 PM

Come on already Brady....get that thing going!

I would try to bleed the clutch again and see what happens, but I'm not as well schooled in manual trannies as some of these guys.

jeffspower · 01-13-2007, 09:33 PM

If the air is all bled out & you don't have a spongy pedal, watch the pushrod/ fork while someone else pushes the pedal down an inch or so. You should see movement. If not, you still have air in the system or a bad master cylinder. Is the clutch slave cylinder mounted so the bleeder is on top? I seen a guy install one once so the bleeder wasn't on top- makes it impossible to get all the air out. If all this checks out, I'd suspect a bad pressure plate (seen new ones bad before, rebuilts are terrible) or the clutch disc is in backwards. The disc has a flush hub on one side & a raised hub on the other. The flush side MUST go to the flywheel side.

HelpMyZ · 01-13-2007, 09:52 PM

the air is all bled out... I've bled it about 20 times at all positions.. the bleeder is on top. the pushrod moves, just not quite far enough it seems.

what I don't get is that if ya push the pedal in it stops halfway to the floor, then when ya loosen a line it creeps to the floor as the fluid comes out.. is that normal?

jeffspower · 01-13-2007, 10:08 PM

Are you saying that the pedal won't go past 1/2 way down at all? like it "hits" something? If so, pull the pushrod boot off the slave & see if the piston is bottoming out on the snap ring that holds it from popping out (at least I think there is a snap ring). If this is what it is doing, It would have to be the wrong throwout brg. or something strange goig on

HelpMyZ · 01-13-2007, 10:13 PM

yeah, thats whats going on... almost like it's hitting something.

HelpMyZ · 01-13-2007, 10:18 PM

is it possible I put the T.O. bearing in backwards or will it only go on one way?

I'm wanting to make sure that it's something in there before I go trying to get the tranny/t-case back outta there

jeffspower · 01-13-2007, 10:22 PM

That's possible. You can pull the fork boot off & shine a light in to see it & if it is in right- if it even moves the pressure plate fingers at all.

jeffspower · 01-21-2007, 03:16 PM

What did ya figure out?

cobinder · 01-22-2007, 12:59 AM

What was the former motor? Flywheel?

01-13-2007, 07:50 PM	#1
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	clutch won't disengage ok, I've got an 87 gmc 1ton with the 4speed sm465 tranny and np205 t-case... I just put a smallblock 350 in it, and can't get the clutch to disengage... anyone have any clues what my problem may be? or what I should try?

01-13-2007, 07:59 PM	#2
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: clutch won't disengage What happens when you start it in gear with the clutch pedal all the way down? Does it creep, or lunge with no slippage? I can't remember- is this '87 mech. clutch or hydraulic? __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

01-13-2007, 08:00 PM	#3
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	Re: clutch won't disengage it's a hyd clutch.. I'm afraid to try and start it in gear... the battery is shot, so it's gotta be jump started... could get messy if it jumps.. haha

01-13-2007, 08:36 PM	#4
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	Re: clutch won't disengage ok, it was in 1st, I just tapped the starter and it lunged forward

01-13-2007, 08:40 PM	#5
68 Stepside huh? Join Date: May 2000 Location: Washington, Illinois Posts: 5,690	Re: clutch won't disengage Come on already Brady....get that thing going! I would try to bleed the clutch again and see what happens, but I'm not as well schooled in manual trannies as some of these guys. __________________ Someday when I'm lonely, Wishing you weren't so far away, Then I will remember Things we said today. RIP El Jay

01-13-2007, 09:33 PM	#6
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: clutch won't disengage If the air is all bled out & you don't have a spongy pedal, watch the pushrod/ fork while someone else pushes the pedal down an inch or so. You should see movement. If not, you still have air in the system or a bad master cylinder. Is the clutch slave cylinder mounted so the bleeder is on top? I seen a guy install one once so the bleeder wasn't on top- makes it impossible to get all the air out. If all this checks out, I'd suspect a bad pressure plate (seen new ones bad before, rebuilts are terrible) or the clutch disc is in backwards. The disc has a flush hub on one side & a raised hub on the other. The flush side MUST go to the flywheel side. __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

01-13-2007, 09:52 PM	#7
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	Re: clutch won't disengage the air is all bled out... I've bled it about 20 times at all positions.. the bleeder is on top. the pushrod moves, just not quite far enough it seems. what I don't get is that if ya push the pedal in it stops halfway to the floor, then when ya loosen a line it creeps to the floor as the fluid comes out.. is that normal? Last edited by HelpMyZ; 01-13-2007 at 10:11 PM.

01-13-2007, 10:08 PM	#8
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: clutch won't disengage Are you saying that the pedal won't go past 1/2 way down at all? like it "hits" something? If so, pull the pushrod boot off the slave & see if the piston is bottoming out on the snap ring that holds it from popping out (at least I think there is a snap ring). If this is what it is doing, It would have to be the wrong throwout brg. or something strange goig on __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

01-13-2007, 10:13 PM	#9
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	Re: clutch won't disengage yeah, thats whats going on... almost like it's hitting something.

01-13-2007, 10:18 PM	#10
HelpMyZ Registered User Join Date: Aug 2006 Location: Virginia Posts: 9	Re: clutch won't disengage is it possible I put the T.O. bearing in backwards or will it only go on one way? I'm wanting to make sure that it's something in there before I go trying to get the tranny/t-case back outta there

01-13-2007, 10:22 PM	#11
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: clutch won't disengage That's possible. You can pull the fork boot off & shine a light in to see it & if it is in right- if it even moves the pressure plate fingers at all. __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

01-21-2007, 03:16 PM	#12
jeffspower Well, Whoop-dee-do! Join Date: Mar 2003 Location: Easton, Mo. pop.- me & scarcely a few others Posts: 2,302	Re: clutch won't disengage What did ya figure out? __________________ '68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD '72 K20 500 Cad/TH400/NP205 SOLD '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car

01-22-2007, 12:59 AM	#13
cobinder Everything is work in progress Join Date: Apr 2006 Location: Denver Colorado Posts: 326	Re: clutch won't disengage What was the former motor? Flywheel? __________________ Good luck with your truck! How much?! It's just an old truck part!! 49 International on a 80 GMC 3/4ton 4x4 chassis 48 International KB-5 2 ton dump bed 04 Honda CRF "500" 09 Honda CRF450 fuel injected rocket 03 Suzuki hayabusa carbonfiber wheeled monster. 02 Ford diesel stretch van (toy hauler) 01 38' Monaco diesel pusher motorhome



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