I am putting together my 32 Ford roadster hiboy... I have an old 327 small block that I'm using in it- and probably doesn't have more than 350 horsepower. The chassis and drive shafter set up for a turbohydramatic 350 with a 6-in tail shaft. A guy on Facebook marketplace is selling one for cheap that looks good, but it came from behind a 250 6 cylinder out of a early '70s Nova. I understand the potential for this transmission to have less clutch discs and maybe a higher stall converter, but do you think there'd be any problems running this behind it that engine in a light 32 roadster? Is it worth a try? Thanks
In my experience, every used TH350 that I've taken apart needed something inside it replaced....so I treat them all as cores that need to be rebuilt. The 6 cylinder transmission, when it's in like new condition, will probably last for quite a while behind the 327 in a light car. If you want to just put it in as is, it might last long enough to pull out of the driveway, or it might last years. You'll probably want to reseal it no matter what, so getting it overhauled while it's out would be a good idea. Or just leave it as is as you build the car, and plan on replacing or rebuilding it before you get the car done, and on the road. If the shop that overhauls it has some spare parts laying around, they should be able to add the extra clutches.
Interesting fact: Back in the late 1977's when GM downsized the big car line (B-bodies) the straight 6 was the base Chevy engine. If you opted for the V8 (305) you got a THM 200 transmission. If the straight 6 was chosen then you got a THM 350. Maybe the 250-6 made too much torque for the new THM 200?
I went to a GM transmission school when the THM200 first came out. At the time is was in one of the small pickup trucks. I was amazed when they started putting it in their big cars. Everything was stamped and cheaply made compared to previous GM transmissions.
Any of you guys have a good idea of what a fair price is to pay a reputable transmission shop to overhaul the transmission?
Couple of hours labor(rate for your area) and rebuild kit. To get an idea, look up Summit or similar places for parts kit. Have a shop within walking distance of my place, and they'll do bench work for cash deals.
If it is just a tired 350 and not a fried 350 you can often find a mechanic who "benches" automatics that does it for a reasonable price. I used to send mine to a guy who told you what kit to buy and where to buy it and he did them for 100 then and that would be about 250 today in his garage at home at night and usually did one a night most of the time. Shop rates are going to be according to what the going rate in your area is. Jim hit a point in post 2. Treat every used turbo 350 that didn't come out of a rig that you actually drove as a core transmission. One of my friends who owns a wrecking yard got so tired of guys bringing back Turbo 350's that didn't work right that he quit selling them to individuals and pulled and sold them all to a guy who picked up transmissions for a rebuilder for 75.00 each. The guy rolled in about once a month and loaded every one he had in the pile, paid him and they were gone.
Well, I went ahead and bought the transmission - got the guy down to $120 so I figured it was worth a try. The fluid looked and smelled good - I pulled the dipstick to about and I stuck a wooden dowel in there and I scraped a whole bunch of the bottom of the pan (which looked like it hadn't been removed in a while) there was very very little gray matter on the end of the wooden dowel when I pulled it out. I'll update this thread in a couple of years when I get the thing out on the road Thanks for the input from everyone!
The TH350 is the first transmission I ever rebuilt. I did it from a book. That one had 60k on it when I sold it, still going strong. I can do one now in about an hour. You can do it too!
Lucky you...I got to start on a cast iron powerglide, age 16, and no facilities at all aside from some cinder blocks and long boards, to remove the thing. I agree that a TH350 is something that you can rebuild yourself. It looks like rocket surgery, but it isn't really.
I am a big TH350 fan.I use them in almost everything.They aren't as tough as a TH400 but are lighter,smaller,and take less HP to drive.I can't rebuild one in an hour,more like 5 hours.There are a lot of good used out there guys swapped for 700R4,$120 is a good price and it probably will work fine.And will outlast the 700.I used them in a drag car in the old days,with a B+M shift kit they worked really well.We tried them in my stepson's street stock and found a powerglide was a better choice.I still build most of my street cars with the 350.I am not saying the 700 is junk,I just put one in my 67 Panel with 4:11 gears,and a 292 6 cylinder,and it made a world of difference over the stock powerglide.I can actually drive it down the highway now.
Need advice on the Modulator situation - keeping in mind that this was on a 6 cyl., is the modulator different from what would be on a 327? The one it came with looks pretty sad, so I want to replace it - not sure what to get... Here's a few pics of the 6 cyl one Here's the one from the 350 long shaft that's going in my truck It's shorter and has an orange band painted around it Are all TH350 modulator valves essentially the same, or are there differences? Any help anyone can provide is well appreciated. Thanks!
The bigger modulator is just an original, the smaller one is a replacement. They only sell one replacement, that I know of. And the replacement has an adjusting screw inside the hole, to fine adjust the vacuum response.
Temporarily removed for cleaning purposes... Thanks for double-checking though, sometimes you guys catch stuff that I overlook
For the life of me, I can't find any numbers on either one of my TH350 transmissions... I've looked in the typical spots, but found nothing. If I could at least figure out a range for the years it was manufactured, then I could get the right transmission filter and pan gasket. The cases on both these transmissions look pretty different, one has a single casting seam down the center, the other has two casting scenes that are parallel to each other in about 10 inches apart to the right and left of center line. The one with two seams came out of a 1974 six-cylinder Nova (but I have no idea if it was original to that car). Anybody have any ideas on how to identify these?
Check the accumulator or governor cover . Codes 1969/1972 I believe are on the accumulator. I lost my mind years ago , so recollection is foggy at best
The accumulator and governor on both transmissions have no markings whatsoever. If you look closely at the two transmissions, aside from the difference ii casting seam lines, the case has some rather different small details.
Unless your 327 is built with at least 10.5 to 1, 202-160 valves and at least an L79 cam you don’t have 350 hp. The highest standard issue was a 300 hp and there were a lot less of those than 250 and 275 hp’s. I’d remove the trans pan clean it and install a new filter and run it. If you’re using an unboltable trans mount taking it out at a later time easily and like others have said upgrade it then.
I believe TH350's take the same gasket-same filter no matter what year. Different suppliers make different styles. I prefer the nylon mesh style that is like the originals. I also prefer the cork style gasket, its softer and conforms better to pans that are slightly bent.
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