shamusj

My '68 442 has been sitting since 1986, car stopped running due to blown head gasket. I'm assuming the trans was fine at time of head gasket blow. Motor is getting rebuilt and should be done early next year.

My question is- is it smarter to spend a large wad of cash 4800-1100 on a transmission rebuild now or is there a decent chance the transmission will work ok after all this time with a simple filter, fluid and exterior seal change.

I've heard the internal seals turn rock hard after a long sit....I'm guessing is no bueno for smooth shifts, etc.

Thanks for any suggestions/ ideas.

I'm leaning towards a rebuild due to the fact that I have almost no free time to play on the car.

Olds64

You could always pull off the pan and see what the valve body and filter look like. It would be cheap to change the filter and fluid and see if it works. FWIW, I had my TH400 rebuilt recently for about $500. The gent included a deep pan from a GM truck. It was a stock rebuild otherwise.

oldcutlass

X2 on dropping the pan and doing an inspection. If the fluid looks nasty or discolored, and there is a bunch of stuff in the pan, then you may want to consider the rebuild while it's out or easy to get out.

billmerbach

Idk but if it was me I would rebuild it now to save trouble later

Killian_Mörder

Is the engine seized, due to the blown gasket?If not and the engine runs but overheats, I'd take it for a short spin, to see what the trannie does. If it doesn't act up, just change the oil and filter, unless there are excessive friction material deposits collected at the pan's magnet and filter

olds3442

I had a extra race trans sit for 10 years ,put in in sons race car it worked perfect, my transmission guy says turbo 350 and 400 are fine sitting as long as they are in dry environment and you change filter and front and rear seals, providing of coarse it was good when you parked it, its worked for me more than once

Professur

Sitting 'shouldn't' have caused it any harm. My first thought was, how many miles did it have on it when you parked it. If it was already long in the tooth, then a rebuild only makes sense. Likewise .. you're having the engine rebuilt ... to original output, or are your taking the opportunity to add a few more ponies?

My humble opinion is that pulling a tranny isn't all that long or involved a process that it must be done while the engine is out. Pressure checks can be done with it in. If it fails those tests, the rebuild itself shouldn't take a pro more than half a day ... it's not going to cost you half a season the way an engine rebuild does. The flip side being ... stuffing an old worn trans behind a freshly rebuild engine is like reusing brake pads after a disk swap. It's a shame you don't have the time to pull it apart yourself ... a trans rebuild is one of those real pinnacle events for a gear head. For so many, it's a black box .. you just don't go there. Once inside tho .... it's like the haunted house at the carnival ... you spend half your time wondering what everyone's so freaked out about.

shamusj

Thanks for all the input- greatly appreciated.

Unfortunately the blown head gasket was left unattended since 1986...water in #1 cylinder didn't do any favors and locked up the engine good...not sure block is saveable...waiting for word from machine shop early next year.

I will drop the tranny pan and filter and give it a once over. Car has less than 90k original miles so theres a chance it will do fine. Will let you know the details.

Two local shops filled my head with lots of talk about internal seals drying/hardening over time...also some mention of the bands...cant remember what they said.

Professur

The chassis service manual has the full tranny rebuild directions ... lets you see and understand exactly what they're talking about. Gives you the edge when they try and smokescreen you. I haven't had to buy a muffler bearing since I bought mine.

redoldsman

If it is fairly clean, I would change the front pump seal, tailshaft seal and the filter.

Olds64

IMHO, the TH400 is the best automatic built by GM. If it is only $30 to install a new filter and pan gasket then you might as well try it. The worst that could happen is it doesn't run and you have to get it rebuilt.

tru-blue 442

x2.

455man

My tranny went out and i didnt have the money for a rebuild so I grabbed a TH400 that had been sitting for 15 yrs. I did a mild DIY shift kit and put a new filter and fluid in it. It's been working fine for 6k miles and barks the tire at WOT. I'd give it a try. Also my 455 had water in a cyclinder and it only required a .020 bore to fix.

Killian_Mörder

27 years is a long time. However, it's only one cylinder and not the entire engine, I would unbolt the rod bearing and move the crank out of the way, in case you were fortunate enough to not have that frozen piston end up at the very bottom of its stroke. Once the crank is out of the way and you thoroughly soaked the piston with brake fluid or any other corrosion penetrator, get out a chunk of wood and a sizable hammer and try forcing the piston downwards. Once there, you could hone away all the rust and get your piston back out. Since these blocks are no longer made, I'd only go as much oversize as necessary, when rebuilding that particular cylinder. If the engine ran properly before the gasket failure, I'd leave the rest of it alone and simply assemble it with a new head gasket, before placing it back into service

shamusj

I like your thinking on the motor- I have the cylinder filled with wd-40 and will do the initial tear down of the motor. It looks extremely clean inside….maybe I will do minimal work and get it running.

Regarding Transmission- thanks to the group I have changed course. I'll drop the pan….if it's clean I'll redo the gaskets/filter and see what happens.