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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: dallas.leavitt on July 04, 2016, 12:27:14 am

Title: 78 chevy C30 camper special
Post by: dallas.leavitt on July 04, 2016, 12:27:14 am

So I bought a "new" truck. 78 c30 with a 454 back by the trusty 4 speed. Only problem is it doesnt stay in second (or third depending on your perspective) gear. If i drive along riding the clutch it doesnt kick out. But as soon as i give it a full load it kicks out of gear. Even if i try and hold it in gear it doesnt stay. What little reading ive done. The only culprit i have found has mentioned issues with snap rings. Im not sure but that doesnt sound right.

All input is greatly appreciated. I havnt started the transmssion tear down yet but in the future i need to.

Title: Re: 78 chevy C30 camper special
Post by: VileZambonie on July 04, 2016, 09:03:12 am

Check the preliminaries: trans mating/bellhousing, engine/trans mounts, linkage, fluids.

Title: Re: 78 chevy C30 camper special
Post by: dallas.leavitt on September 19, 2016, 11:32:20 pm

So its been an awful long time. But I got the transmission out. Not apart thoough, so im on the hunt for a good rebuild kit.

There are no linkages in this 4 speed I think. Unless you count the shift forks. What would be a good kit for my money. I saw a kit by synchro king that seemed nice. Plus I have been eyeing novak adapters web page for awhile. I like the set up. It will let me easily order the kit. (And what i think maybe my problem) Third gear relatively easy.

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Title: Re: 78 chevy C30 camper special
Post by: dallas.leavitt on September 22, 2016, 09:44:32 pm

Got into it today. Pulled off the top cover. Input bearing cover and shaft out. Had to buy a socket for the output yoke.
Nothing seems to be sticking out to me why it was kicking out of 3rd gear.

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Title: Re: 78 chevy C30 camper special
Post by: Jason S on September 23, 2016, 08:45:03 am

You might take a look at this:  http://www.fourwheeler.com/vehicle-reviews/131-0208-sm465-transmission-rebuild/ (http://www.fourwheeler.com/vehicle-reviews/131-0208-sm465-transmission-rebuild/)

In the link, it gives some specs on the SM-465 and describes why third gear jumps out and what they did to remedy the problem.

You might want to do a search for "SM-465 third gear fix" or similar. There are sleeves, collars, synchros and other items that are used for this.  Don't know anything about it, but on ebay there is a "GM SM465 Updated 3rd Gear and 3-4 Slider Torque-Lock" that is supposed to eliminate the problem.

Title: Re: 78 chevy C30 camper special
Post by: dallas.leavitt on September 24, 2016, 09:29:56 pm

Thanks I took a look at anahiem gears stock. They don't have a kit in stock it looks like that includes synchros. I get my transmission apart and my synchros don't look too bad. My big problem comes from what the diagram I am using 3rd gear speed blocker ring.

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