Anybody good with auto transmissions

[VTJUNK]

I'm posting here because this will get more attention and quicker answers I bet. I have a 70 GMC 1/2 ton truck with a 66 Buick Skylark GS motor and trans. The truck was parked for the winter and when I started it this year, it had drive and reverse, moved once, then only had reverse. No hint of engagement in any gear except a good solid reverse, and of course park. Pulled the pan, fluid was normal, no abnormal amounts of material in the pan, linkage was hooked up and working. I'm not against pulling the engine and trans and putting in a 350/350 combo, but what could be wrong with this all of a sudden?

[CTX-SLPR]

Re: Anybody good with auto transmissions

Thats a 401 Nailhead and ST300 combo right?

[VTJUNK]

Re: Anybody good with auto transmissions

Well, you got the 300 part right. I believe it's a 300 anyway. The trans is a 3 speed auto, whatever they called it. I don't know much about it actually, I just kind of inherited it.

[CTX-SLPR]

Re: Anybody good with auto transmissions

If its a stock A-body GS drivetrain it would be a 2spd switch pitch ST300, if its 3 speed and no switch pitch but shifts like an AOD, ie hold 2nd by shifting into D then back into L, its a '64 ST400, if its a switch pitch its a '65-66 fullsized car SP400. If its a plain 3spd with a normal shift pattern its a converted version of one of the fullsized 64-66 ST/SP400's. The SP400 didn't show up till '67 in the A-body.

[IndyShiftman]

Re: Anybody good with auto transmissions

For whatever reason you have no forward clutch. Trans has internal problem. You would have to disassemble to find the problem.
Basically, trans is old, who knows how many miles is on it. Needs rebuilt.

[whiplash]

Re: Anybody good with auto transmissions

For whatever reason you have no forward clutch. Trans has internal problem. You would have to disassemble to find the problem.
Basically, trans is old, who knows how many miles is on it. Needs rebuilt.

That is a focking beautitul car ,,,,,howie shitttttttttttttttttt, ooops exuse my language, but Ma Ma has a weakness for 67 Camaro's......wooooo ahhhhhhh

[VTJUNK]

Re: Anybody good with auto transmissions

I disassembled the valvebody and cleaned it, removing all the valves, checking for any debris, none found, reassembled, still the same result, but now it engages drive, but still doesn't move. Time for a rebuild alright, a rebuilt th350. The truck belonged to my Dad who gave it to me when he bought a nice one owner '72 Chevy C-10. I plan to fix the GMC to be my tow rig, as I am without a truck right now. Will look sweet towing my 70 C-10 to the track. ;D

[IndyShiftman]

Re: Anybody good with auto transmissions

For whatever reason you have no forward clutch. Trans has internal problem. You would have to disassemble to find the problem.
Basically, trans is old, who knows how many miles is on it. Needs rebuilt.

That is a focking beautitul car ,,,,,howie shitttttttttttttttttt, ooops exuse my language, but Ma Ma has a weakness for 67 Camaro's......wooooo ahhhhhhh

LOL, Thanks Whiplash. ;D

[CTX-SLPR]

Re: Anybody good with auto transmissions

What engine is this attached to? There are no Nailhead pattern TH350s and probably cheaper to rebuild this than to by one of the GOOD adapter kits.

[VTJUNK]

Re: Anybody good with auto transmissions

I will put a SBC in it. I don't know why anyone thought the Buick engine was a good idea. Nothing wrong with it I suppose, probably what the person had laying around. Seems a 350 would have been easier to put in it, or another th350, which ever went bad first. The trans in question is a 3 speed auto, must be later than I was told. The air cleaner said Buick 340, so that should be a good clue as to what this is exactly. The engine ran good, so I don't know what I'll do with it.

[CTX-SLPR]

Re: Anybody good with auto transmissions

Here's a quick way to tell what it is, is the distributor in the back or the front? Back its a nailhead, front its a later engine and probably a 66-67 340 with a BOP-C bellhousing. If it really is a nailhead, its worth quite a bit as that rear sump oil pan and exhaust manifolds are 65-66 GS only items.

[VTJUNK]

Re: Anybody good with auto transmissions

I knew it wasn't a Nailhead. The dist. is in the front. Buick 340, is that CID or torque rating?

[CTX-SLPR]

Re: Anybody good with auto transmissions

CID, unusual motor used as a stand in for the larger cars till the '68 350 came out. A 355 is a 4bbl 300 64-65 after which the 340 took over as the higher motor in both 2bbl and 4bbl form and the 300 was just a 2bbl base motor making the '65 iron 4bbl for the 300 a bit of a hot comodity since the '64 aluminum one doesn't fit the later iron heads very well.

[VTJUNK]

Re: Anybody good with auto transmissions

Wow, there's definitely an education to be had there. Thanks for the info!

[squirrel]

Re: Anybody good with auto transmissions

340 ci engine had 340 ft lbs torque, so it's probably a 340 engine.

If the trans is the one that was usually used behind that engine, then it's a 2 speed ST300, kind of like a powerglide inside, but looks kind of like a TH350, and a Buick-Olds-Pontiac TH350 would bolt right in place if it, although you'd have to add a kickdown cable.