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Technical Is someone blowing smoke up my wazoo?

Discussion in 'The Hokey Ass Message Board' started by Joe Romano, Jan 14, 2016.

  1. Make a long story short, I have a TH 350 trans that this rebuilder guy told me was for a 6 cylinder.
    I don't know shit from shinola, so is he blowing smoke?
    I never heard of such a thing as, a 6 or 8 cylinder TH 350.
    To me a Th 350 is a Th 350.
    If he's right can I team it with my 350SBC?
    If I do how long do you think it would last?
    I dont drag or race, but once in awhile I like to hear the 4BBl kick in.
    Joined: Nov 10, 2005
    Posts: 846

    from Holly

    Your trans guy is referring to the internals of the trans. The 6 cylinder trans has less clutches and more light weight components in it. Many years ago I learned not to interchange the front pumps etc.
    loudbang likes this.
  3. Bolt it up and go.

    They made one for trucks that had more clutches and had a bigger clutch drum to handle them but other than that it is the same kit to rebuild a 6 cylinder tranny and an 8 cylinder tranny. You can chuck the clutch drum up in a lathe and clearance it to make the extra steel and friction plate fit by the way.

    They also made a T350 for the HP Corvettes tat was a little beefier, but your standard cars all got the same transmission.

    How much was he going to charge you to convert it to an 8 cylinder transmission? :rolleyes:
    1927graham likes this.
  4. DDDenny
    Joined: Feb 6, 2015
    Posts: 14,852

    from oregon

    As long as it doesn't have a BOP case it will.
    It may have different torque converter values, but based on your description of intended useage, it should work fine.

  5. He didn't say. He took it apart said it was fine except for a bushing.
  6. LOL usually they tell you something won't work just before they try to sell you something that will. A friend that I worked with dropped 12oo dollars on a "truck" transmission for his Silverado when the guy in the transmission shop who could tell just by looking at it that someone had adapted a "car" transmission to his truck. Pretty easy to tell a truck T350 from a car T350 by looking at the outside of the case. :rolleyes:
  7. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,021

    from Quincy, IL

    I know this thread is about TH350.........but just for reference....there were 6 cyl and 8 cyl versions of aluminum case Powerglides. Asides from have air cooled converters with holes in the bellhousing portion of the case, they also had slightly different first gear ratios, 1.76 for 8's and 1.82 for 6's, as I recall.

  8. Going from memory here, there were light duty T350 as used in Vega's and Monza's. These had roller bearings instead of bushings in places, and had planetary shells with holes in them for lightening. All of this to reduce the hp loss from rotating mass and friction, and the extra strength was not required. These trans parts were popular in the stock and super stock racing classes as they were always looking for that fractional benefit advantage.

    Also the old poor man's looser torque converter was to use a Vega converter in your T350 or T400 behind a healthy V8.
    loudbang likes this.
  9. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    Member Emeritus

    The later style sixes, the 194-215-230-250-292 engines, have the same bell-housing, bolt to flange area the V-8's have, so any transmission can be used as long as it has the same pattern. The Vega/Monza TH350's were in reality, TH250's (as were some used in V-6 and small V-8, late 70's/early 80's Malibu's and the like), and had a different bell-housing to fit the 4 cylinder engines they came on. The TH250 also has an externally adjustable band the TH350's do not have. As far as the "V-8" TH350 transmissions go, there's really no difference in the cases, or MOST of the hard parts inside. The difference lies in the thickness of the apply PISTONS, not the drums; thinner pistons allow for more clutch discs and steels, thicker pistons when less are required. The gear ratios are the same. The sun shell on the 4 cylinder (and some lo-perf V-6/V-8) models has 5, 1 1/2 inch lightening holes around it's periphery; it's a racers "trick" to use that lighter weight sun shell to help reduce rotating mass. Some of the lo-perf transmissions were also air cooled, like some models of the aluminum Glide were. I'm not too sure how a mechanic/rebuilder could tell a car VS truck TH350 apart from one another, just by looking at the exterior, unless it was an air cooled unit; he probably made the call on what he found inside of it. There are different overall lengths to the TH350, depending on the output shaft/extension housing length, and that depends on what it was meant for; most TH350's have a 6 inch extension housing, some full size cars and trucks had a 9 inch extension housing, and then there's a really long one used in some Olds/Ponts. As far as using a lo-perf transmission behind a different engine than what the factory assembled it for, no problem, although it won't last as long, particularly if you're hard on it. TH350's never came behind BBC's, they were used in some of the bigger engined B-O-P cars, but a lot of racers have built TH350's to survive behind a BBC. Weakest part in a TH350 is the intermediate over run clutch outer race; they frequently break with hard 2nd gear shifts, so most replace the race with a hardened one, and update the roller clutch along with it. The intermediate clutch accumulator spring also breaks quite often, and most guys never even know it's broken until rebuild time due to other reasons. A couple of companies are making heavy duty intermediate drum/roller/race assemblies, similar to what the TH400 uses, but it involves machine work and they are $$$. There's also a mechanical diode now in use that really steps up the holding power and longevity of the intermediate drum/clutch assembly, and it too is $$$ (I have one I'm going to be trying out). Ron Session's has a good book out on the TH350 transmission, but even it does't have all the latest tricks and modified parts out there now. I am Butch/56sedandelivery.
    loudbang likes this.
  10. Larry Anderson
    Joined: Jul 15, 2013
    Posts: 170

    Larry Anderson

    Correct, correct and correct to all of the above. Had a '76 Vega with the air cooled "TH350" followed by a '79 Malibu with the base 200ci, 90 degree V6 (same bolt pattern as a small block) backed by a TH350 during my initial driving years. My dad thought zero horsepower in a somewhat solid platform was safer for his 16 year old kid than the polar opposite. We did have an issue with the TH350 in the V6 Malibu that was easily cured with his "Warranty" rubber stamp as a Chevrolet Zone Service Rep and a rebuild at Lyman Slack Chevrolet. The inners were a bit weaker in some aspects and applications, but the outside and bolt up is the same.
  11. So I guess I'll put it back in...... I just have to be kind and not hammer it... I don't need the expense... Thanks, Joe

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