Transmission or Clutch Problem??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cowboy13 · 10-01-2019, 11:47 PM

Driving down the road in my 1970 K20 Chev and all of the sudden it feels like it pops out of gear. Truck lurches and loses acceleration. I can still freely shift it using the stick but the truck has no forward momentum, just revvs up when i step on the gas. Pull over to the side of the road, shut the truck off and start it back up again and it works and runs fine. Any ideas whats going on? Thanks for any help.

**jocko** · 10-02-2019, 12:10 AM

What type of manual trans?

Check trans fluid level and shifter linkage. If all good, may be time for new trans synchros.

Cowboy13 · 10-02-2019, 12:30 AM

As far as i can tell from the stampings its a Muncie SM465 with a NP205 transfer case.

BigBird05 · 10-02-2019, 03:24 AM

You didn't say how the clutch peddle felt. Could it be a clutch problem.

Bigdav160 · 10-02-2019, 03:47 PM

Sounds like a clutch. Does it seem to work ok in low gear? Start out slowly, upshift and try to accelerate hard. If the clutch is bad it will slip then.

Cowboy13 · 10-02-2019, 11:06 PM

BigBird,
BigDav,
I was leaning more towards it being a clutch problem to. Clutch does feel like it could use some adjusting. It is ok in the lower gears. I know there is a cover underneath that i can remove as well to inspect the clutch plate, but not to sure what i would be looking for.

I appreciate all the help and info guys!!

My Baby:
70' K20 Flat Black

71gmcC15 · 10-03-2019, 01:50 PM

Some times my sm465 likes to fall out of 3rd. It make a grinding sound and it slips out. Have to put in N then back into 3rd. Is that what is happing to you?

10-01-2019, 11:47 PM	#1
Cowboy13 Registered User Join Date: Mar 2016 Location: Portland OR Posts: 14	Transmission or Clutch Problem??? Driving down the road in my 1970 K20 Chev and all of the sudden it feels like it pops out of gear. Truck lurches and loses acceleration. I can still freely shift it using the stick but the truck has no forward momentum, just revvs up when i step on the gas. Pull over to the side of the road, shut the truck off and start it back up again and it works and runs fine. Any ideas whats going on? Thanks for any help.

10-02-2019, 12:10 AM	#2
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,954	Re: Transmission or Clutch Problem??? What type of manual trans? Check trans fluid level and shifter linkage. If all good, may be time for new trans synchros.

10-02-2019, 12:30 AM	#3
Cowboy13 Registered User Join Date: Mar 2016 Location: Portland OR Posts: 14	Re: Transmission or Clutch Problem??? As far as i can tell from the stampings its a Muncie SM465 with a NP205 transfer case.

10-02-2019, 03:24 AM	#4
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,305	Re: Transmission or Clutch Problem??? You didn't say how the clutch peddle felt. Could it be a clutch problem.

10-02-2019, 03:47 PM	#5
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: Transmission or Clutch Problem??? Sounds like a clutch. Does it seem to work ok in low gear? Start out slowly, upshift and try to accelerate hard. If the clutch is bad it will slip then. __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

10-02-2019, 11:06 PM	#6
Cowboy13 Registered User Join Date: Mar 2016 Location: Portland OR Posts: 14	Re: Transmission or Clutch Problem??? BigBird, BigDav, I was leaning more towards it being a clutch problem to. Clutch does feel like it could use some adjusting. It is ok in the lower gears. I know there is a cover underneath that i can remove as well to inspect the clutch plate, but not to sure what i would be looking for. I appreciate all the help and info guys!! My Baby: 70' K20 Flat Black Last edited by Cowboy13; 10-02-2019 at 11:14 PM.

10-03-2019, 01:50 PM	#7
71gmcC15 Registered User Join Date: Feb 2018 Location: Doland SD Posts: 836	Re: Transmission or Clutch Problem??? Some times my sm465 likes to fall out of 3rd. It make a grinding sound and it slips out. Have to put in N then back into 3rd. Is that what is happing to you? __________________ ( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original ) 94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless 07 gmc sierra classic rcsb 4.3 lt 5 speed w/t 04 chevy Silverado 1500 ext cab 5.3 4l60e. 81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)



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