SBC 350 / TH350 ?

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Jun 23, 2002
Looks like I've changed my mind......TH350 is the way im leaning now. The chevy 350 I bought was from an automatic so I dont have the bellhousing/flywheel/clutch/fork ect. I was given a TH350 that I can use as a core,and I like the convienience of the automatic transmission for daily driving, the gear ratio is almost the same as the L/C 3spd and then there is the added benifit of the torque conv. multipling the crawl ratio ?....although the lack of engine braking for downhill is a problem. I was thinking that a lockup converter would be the way to go to compensate for that. The A/A kit provides the propper tail shaft and the motor is going to be moving forward anyway. I was told to figure on some drive shaft work with either the 3spd or the thats the same. The cost of adaptors is within about 150-200 bucks when the additional parts I would need for the manual trans. So what do you guys I making a mistake ? seems like the same set up as the stock 3 spd (gear wise) The only other auto trans would be the 700R..but nobody has given me one of those latley.
Since you asked for it... The gearing on the 3 spd blows. To me that would be a big negative. If it was me I would put on either an SM420 for serious gearing, or an SM465 for better road manners and good gearing. But I'm biased cause all autos suck as far as I'm concerned, I have no problem with driving a manual day to day, I already do and its about as bad of a tranny for street driveability there is. (LC 3 spd). Just my opinion.
Well my opinion if your using the th350 is go with a 203 doubler or a toybox. The 203 doubler will only have you buy one adapter for the back. you can put the 3spd, 4spd, split case behind the 203.. But you only get 2 to 1 in the doubler. The toybox with the Downey adapter will net you as low as you want to go but it's pricier.. Then again.. you get what you pay for in the gear dept.
You might be able to leave your tcase in it's proper location and still get a doubler if your careful about placement of the engine.
I dig it. I'm running a SBC350/TH-350 to stock 3 Speed in my 40 using a Downey adapter. I wont be going back to a manual any time soon. Never thought I would want an auto, but it crawls with out ultra low gears. Its like cheating! I can use my brakes at the same time as the gas... no rolling, popping the clutch or using the handbrake on hills. The adapter is only about 1.5" long and its pretty cheap. Lets me use stock rear driveshafts. Yes, using your brakes instead gearing sucks on the downhills. Lower gears wont help too much with this. Get disc brakes. :G
schlaker: Thanks for the input..the couple of 40 owners that Ive talked to have had the same experience with the auto...thats why im going to go that way. I was leaning towards the Downey adaptor...but how did you handle the front driveshaft clearance ? they have the output shaft kit that is supposed to clear the transmission, did you use that ? Which shifter did you use ?

Thanks Jeff
I, like Bailey was a manual tranny only driver for years and wouldn't touch an auto, but now that age is catching up with me plus very bad back etc, an auto is the only way to go. If you use a lock-up torque converter and opperate it off of a togggle switch it may give some engine braking since it's basically 1 to 1. Schlaker had the key when he said disc, front and rear, and even a driveline disc brake could be mounted and hand opperated.
I've seen Downey's drive shaft flange/joint kit in thier catalog and it looks like the ticket. Unfortunatly I had already put together a custom drive shaft using similar parts. (Spicer 1210 u-joint and a nissan yolk). Its a really close fit; had to grind off the lip that hangs down at the edge of the tranny oil pan. But it seems to work fine - survived 3 Rubicon runs and a Fordyce trip last summer. As for the linkage - I built an aluminum bracket that I had welded to the passenger side of the TH 350 (basically just a flat plate with a hole in it). If you locate it right you can bolt on the stock FJ40 shift pivot pin and use all the stock 40 linkage in original locaton with out any modification. I didnt even have to cut up the tranny cover.

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