I recently bought '66 Chevy C10 longbed. I'm new to the mechanical side of things and I'm learning as I go, so I could use some help. The problem is that it feels like it needs another gear and on the highway it sounds like my engine is going to explode. It originally had a 283 but now it has a 305 with the stock 4-speed tranny. The engine runs great so there are no problems there. Is it just a bad engine/transmission combo? Any suggestions?
Go to a transmission shop. Ask them to tell you what gear ratio is in it. You might want to run a set of 3:05's or 3:25s
Could just be really deep rear gears. There shouldn't be any difference between engines unless you swapped exhaust with the 305 and it's just more noticeable now.
Longbed tells you its a Heavyer Duty so it'll have bigger payload gears to haul, it'll scream on the freeway. Get an overdrive or change the rearend gears or whole rearend with something 3:50 or lower. You could count the driveshaft rotations per one tire rotation to see what gears are in there. You probally have 4:11s or 4:56 (4 to 4.5 driveshaft rotations) You could also get bigger diameter tires to bring down the revs.
Buy ear plugs! When them things were new we ran them at 65-70 no problem,SBC will cruise at 3500 RPM all day and not care.
If you have the old HD 4-speed, the rears gear rations in those could be very steep, like a 4.11 or better. I had a C30 truck with either a 5.13 or 5.38 rear and it was wound up by 55 MPH. Just make sure you have it in 4th gear before doing anything else. Bob
Thanks for the replies. I think I'll take it to a transmission shop when I get a chance. Maybe I'm just not used to how it sounds yet.
OOps... I spoke before reading properly. Make sure it's shifting into 4th. If it is, I suspect there are quite a few 66 compatible C10 bolt in rears that already have taller gears out there for cheap if you keep your eyes on Craigslist and the junk yards. That truck arm rear suspension was used for a long time in Chevy trucks.
Been down the same road with a '65 C-10 at 70 MPH your are probably turning about 3600-3700 RPM I swapped in a 700R4 overdrive that dropped it down to a nicer 2400-2500 RPM also gained about 3-4 MPG. With your 305 a 200R4 is also a nice swap look for a 1988-91 donor with either transmission those have the latest lubrication upgrades and are non-computer for EZ hookup.
mine had 3.73s. at 60 it was turning 3,000 rpm. at 70 and above, your really humming. Lower aspect ratio tires make it turn more rpms. If you are not used to an older truck, it'll sound like its going to grenade. I ran mine for years, then put a set of 3.08s in it. An O.D. trans will lower the rpms to the low/mid 2,000's rpm ange at 60. If you are not used to non O.D. trucks, this was the norm.