1970 Pontiac Laurentian Transmission ID

70Laurentian · Newbie

1970 Pontiac Laurentian Transmission ID

4SPEED427 · A Poncho Legend!

That sure looks like it but the simplest way to tell is if your oil pan is shaped like this:

www.ebay.com/itm/USED-CHEVY-TH-350-OIL-PAN-AFTERMARKET-GM-GOOD-SHAPE-NO-BOLTS-NO-GASKET/254391797687

seventy2plus2 · Canadian Poncho Superstar!

Or look to see if it has a kick-down cable mounted on the carb. If equipped, it'll be on the bottom of the throttle shaft. If it has a kick-down cable, it's a turbo 350.
There was a mid-year change from throttle linkage to cable, and as such the Turbo 400 kick-down switch moved from being mounted on the carb (with throttle linkage) to being mounted under dash (throttle cable).

seventy2plus2 · Canadian Poncho Superstar!

Or where is the modulator valve on the tranny? That's the thing that the vacuum line from the engine goes to.

For a Turbo 350, it's way towards the back by the tailshaft. On a Turbo 400, it's on the forward part of the tranny, kind of near the starter.

seventy2plus2 · Canadian Poncho Superstar!

And now that I look at the photo on my pc instead of my phone, I'd say that's a Turbo 350. It looks to have the small speedo gear housing, and also looks to have a small tranny yoke that uses the clips on the u-joint. A Turbo 400 yoke is larger, and has the different u-joint retainers.

cdnpont · Canadian Poncho Superstar!

350 for sure. A 400 has 6 bolts on the tailhousing, 350 has 4. A 400's speedo cable goes into the case, not the tailhousing.