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Old 10-01-2019, 11:47 PM   #1
Cowboy13
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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.
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Old 10-02-2019, 12:10 AM   #2
jocko
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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.
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Old 10-02-2019, 12:30 AM   #3
Cowboy13
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Re: Transmission or Clutch Problem???

As far as i can tell from the stampings its a Muncie SM465 with a NP205 transfer case.
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Old 10-02-2019, 03:24 AM   #4
BigBird05
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Re: Transmission or Clutch Problem???

You didn't say how the clutch peddle felt. Could it be a clutch problem.
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Old 10-02-2019, 03:47 PM   #5
Bigdav160
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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.
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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
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Old 10-02-2019, 11:06 PM   #6
Cowboy13
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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.
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Old 10-03-2019, 01:50 PM   #7
71gmcC15
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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?
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( 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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