Technical Turbo 350 variations

I'm looking to install a T.H. 350.
I've never understood the reason for the difference lengths in the T.H.
6", 9" or 12" tail variations are available.
Why wasn't one sized 350 used with various drive shaft lengths ?

 

Drive shaft length gets critical. For instance a new F150 has a one piece shaft for a 6' bed but 2 piece for 8' bed.

 

good question...I think the longer ones were used to minimize driveshaft length. Usually found in long bed trucks, wagons, bigger cars like Cadillacs (although that's the th400, not the 350).

 

Small world, I recently moved from Ellijay GA to Hendersonville, N.C.

 

don't forget there is also the th350C trans, which is the converter lockup version, they have a electrical connector on the case

 

...and the almost versions, the TH250 and TH250C, which have a band adjuster on the front of the case....

 

Should I be looking SPECIFICALLY for a 6" or 9" or does it not make any difference ?
Reading here and there, I see the 12" 350 is not a common unit.
Is one more desirable than another ?

 

The 12" tail shaft is not common.I found that out recently when my 350 TH needed work.

 

I had a 350 in 75 Chev G10 van. It had a boss on driver side pan rail to mount neutral safety switch and back-up light switch. Might be a problem solver for some.

 

The short transmission is good if you are replacing a manual trans or powerglide, and don't want to cut the driveshaft. The longer one (9" tail) is good if you are planning to someday upgrade to a 700R4, since the overall length is the same (the mount is 2" forward). then again, a the short TH350 can be easily replaced later by a 200-4R, if you can move the crossmember back far enough.

It really doesn't make much difference...

 

This is helpful to me, knowing that I'm going from stick to auto. My current 3 speed "stick" is a 1959 3 speed stick with overdrive though, am wondering if this version of stick tranny is the same length as a regular 3 speed stick WITHOUT overdrive.

 

Some of the 3 speed transmissions in the late 50s-mid 60s were shorter, but the long ones, and all of the 3 speed with overdrives, are all the normal 28" overall length (including bellhousing).

 

Thank you !

 

Chevrolet version, and BOP version.....Buick-Oldsmobile-Pontiac bolt pattern.
In my modified I have a universal version.....the dual bolt patterns fits all four engines

 

Still preparing for the conversion of the stick 3 speed / overdrive to a TH 350.
After installing the TH 350, I want to use a kickdown cable.
Being that this engine (see avatar) has a FENTON dual carb intake, is there a specific place where the TH 350 kickdown bracket should be located ?
Has anyone out there used a TH 350, with a dual carb setup, on a 235 " ?

 

I don't know about the carb setup you have...should be fun to figure out. The cable needs to be pulled tight at full throttle, it only does something in the last little bit of travel. So it's not that hard to get it working. The original 6 cylinder applications used a kind of long cable, and brackets to mount it are probably hard to find. But you can also connect the cable to the throttle linkage somewhere besides the carb, if that would make it easier. Some of them even had it go through the firewall, and connect to the top of the pedal arm. Although this trick only works if you have a cable for the throttle linkage.

 

If you are going from a 3 spd/ overdrive to a turbo 350 , how will that affect your engine rpms on the road with that engine?I know it will increase the rpm , but would it be better to go to an auto with overdrive instead of the Turbo's 1-1 final gear?

 

As a side note, there is one more "variation" in terms of length; There is a shorty kit available that eliminates the tailshaft altogether. Good for dragsters/altereds/anything with limited space.

Don't have time to find the link, but it's out there.

 

He's a chart and a friends blue flame with triples in his 35 Cheby roadster with T400 behind it via an adapter kit. 60" is roughly the maximum length for a single piece tailshaft. You need to factor in critical speed with length and diameter.

 

Thanks for your comments, Jim.
The carb set up is shown in the avatar, dual Rochester single bbl carbs, with no throttle cable.

 

Very good question.
The engine is a modified 235 (in avatar), the trans is a '59 IMPALA 6 cylinder 3speed / overdrive.
The kicker is here. The rear is a Ford 9" with a 3:50 ratio ....... a tough gear for the overdrive tranny.
My clutch knee is a new knee, not the most comfortable to do clutch work ....... so the 3:50 gear ratio will stay, while the TH 350 will be added.

 

Although I cannot find manual tranny lengths right here and now now, I believe the TH 350 with the 6" ext. will be close in length to the manual.

 

Thanks for those measurements, would like to see a pic, as to how he connected his tranny kickdown cable to the carb linkage.

 

Although this is the drivers side view of an EARLY 235" TRIPOWER CORVETTE linkage, the linkage is basically the same on my '51.
The bellcranks shown (group 3.579) are common to mine.
Of course, on my specific application, there is no linkage rod, going to the powerglide, as shown in this illustration.
http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0303.htm

 

if you can attach the cable to that lower bellcrank it should do what you want. But the cable might be too long for that...unless maybe you get one of those aftermarket street rod type that you can cut to length?

lokar makes them for big bucks, spectre for medium bucks, you might get what you pay for. Or maybe not

 

Thanks !

 

A 6 inch extension housing is the same length as your 3 speed/overdrive manual transmission setup. You will need a different, 27 spline slip yoke however. The kickdown cable on a TH350 really is't needed; both the Summit and Jegs branded TH350 transmission have the cable hole in the transmission plugged as examples. You just don't have a kickdown passing gear; you have to pull the transmission down into a lower gear manually, and then upshift it manually. In drive it shifts fully automatically You should be able to sell your 3 speed/overdrive fairly easily; they are in demand. I am Butch/56sedandelivery.

 

I can't stand driving a car with an auto trans, and kickdown not working....

 

Thanks for verifying the overall tranny lengths, when comparing the two trannys.
Two thoughts here, one regarding the current overdrive tranny, the other regarding the kickdown.
You say these 3 speed stick trannys, with overdrive, are favorable units to own.
I will have two to sell, once this conversion happens .... the one currently in the car, and the extra one I have, as a back up unit.
Any vehicle I owned in the past, had an operational kickdown.
That being said, here is my concern and question.
If the tranny shifts OK without the kickdown cable, how does the tranny shift, under a harder acceleration ?
IF the tranny shifts "too quickly" under harder acceleration, instead of holding back in each gear, that would not be desirable.
Any thoughts on the upshift "shift points" under harder acceleration?
I, myself, don't have that answer.

 

I have not experienced what you say, but would imagine it would feel like something is missing.