Hi there. Been around about 10 years here, owned a few third gens. Just picked up a 86 Z28 with a mildly built 350 and th350 trans. First thing I noticed driving it, is that it doesn't downshift when I mash the pedal. Turns out there is no kickdown cable. I know jegs and summit sell them this way and even go so far as to put a block off plate on the trans and state that puncturing that will void the warranty. Why Is this?

It also feels like the rpms build slowly. Is this a function of the gears being taller since it's only a 3 speed? That in mind, any recommendations on a stall and rear end gear combo? I've never driven a car with a th350, so I'm pretty unfamiliar. Any insight is appreciated.

 

Who knows? Sounds kinda like a HUMAN thing. Those weird things are completely unpredictable and weird. Asking "why" any of em did anything is a fool's errand.

That said, all that cable does, is yoink the transmission into 2nd gear when it's in 3rd. Very crude. Definitely handy to have though.

The T-350 1st gear was about 2.5something, don't recall the exact #. Kinda close ratio by 2025 standards. Butt then, the torque converter stalled at about 1600 or so, which pinned the motor down to sub-2000 RPMs most of the time, in yerbasic typical 2.73 or 3.08 (3.08 was an EXTREMELY common gear back then) rear end. If your car has the typical 2.73 that came in those cars with the LG4 auto, that's why it feels like it can't leave a traffic light, and takes about a half mile before it starts to feel like it's getting into motion. Poor cam choice will make that whole scenario even worse; if for example you have the "350 HP 327" POS (part number ending in 151, .447"/.447" 222°/222°), you're doomed. After ALL THESE YEARS, people STILL fall for that "350 HP 327" CRAP, not realizing that the 327 that the cam came in had over 11:1 compression, a 4-speed, and 3.73 gears which people usually changed to 4.56 so it would have some LEAVE. That cam, and many others, are a COMPLETE mismatch to a low-compression engine, auto trans with stock converter, and typical grocery-cart gears.

Try 3.42 rear gears and about a 2800 - 3000 RPM converter. Get one of smaller diameter than the typical stock 11" if you can. You'll need to add a cooler most especially if you put in the converter before the gears, because a low gear will force the "theoretical" engine RPM to be below the converter stall, which means, it will ALWAYS be slipping, even when driving down the road cruising. Whatever power the engine is producing in that situation, that doesn't go to the wheels, ends up in the fluid in the converter. Few things will burn up a transmission faster than that. Personally I'd put the gears in first. You may even find that with halfway decent gears the stock converter isn't near as bad. Then all you have to worry about is whatever bad cam choice the PO made.

 

@sofakingdom. Thanks for the insight. Gears first is a good play, I think. Probably a little less work than putting in a stall converter anyway. I have no idea what cam was put in there. But it definitely sounds like it's got a fair amount of overlap and duration. I have a 350 I built about a decade ago that will eventually go into the car. For now it's just a drivable project. I've got enough to keep me busy on it in the meantime haha. 3.42 was what I was leaning towards. So, good to hear I wasn't out of my mind on that one.

Regarding the trans, it shifts consistently and firmly, downshift as I come to a stop without issue. I'm guessing the modulator is working properly. But I figure it's worth pulling it out and cleaning it up, maybe replacing. Seems easy enough to do. Figure I'll just add a kickdown cable and bracket, rather than use a ratchet shifter or something similar for WOT downshifts.

 

TH350 been around for decades. Had a few. There has to be a kickdown cable installed. Doe the rebuilder want u to downshift each time for a "passing gear"?

 

Definitely isn't one there. I can address that easily enough. I was more curious as to why a major company like summit and jegs would sell them not only without a kickdown;,but a block off plate and a disclaimer that puncturing it to add one will void the warranty.

 

Steve; They expect u to obtain the additional hardware from an old core.

 

Follow up question on the th350. I plan to clean and possibly replace the vacuum modulator. I understand you can turn the screw in them to adjust shift points. Even when I get into the throttle pretty good, it shifts at about 4000 rpm. It feels early to me. I'm not sure how accurate the tach is, as it's aftermarket. Any thoughts?

 

Steve;
yes u can adjust a small screw in the vacuum modulator. I had to do that because the TH350 in my 1972 Buick GS (sold) would not shift from 1st to 2nd without playing with the accelerator pedal. I would live with the 4000 rpm shift.

 

There are 4 common vac mods for 350. Big back can, and 3 small gold cans; each has a stripe, one magenta, one green, and one red. You want the small gold one w red stripe. NOT the big black can, and NOT the magenta or green stripe. RED stripe only. It will be listed in the computers at the stores by application; since they all also fit PG and 400, you can look up ANY 60s/ 70s application, look in the box, and keep trying until you find the right color stripe. Start w, say, 69 Vette w 396.

Then AND ONLY THEN go to work on adjustment. Clockwise makes it shift later and harder . Quarter turn increments should make a noticeable difference.

 

Excellent. Thanks.

 

Need some help here on my 82 z28 it’s leaking bad what do I need to do to fix this please help I’m pretty sure it’s the dipstick tube???

 

Posting that same question and pic in about 75 different threads isn't going to do you any more good than just asking it once.

The leak exists precisely where the fluid is coming from. Once you take the car to the quarter car wash and clean it up, instead of 10,000 years of funk and grunge buildup, you'll be able to see nice fresh fluid coming from the leak. Then you'll know where the leak is.

Although, it looks like the fill tube seal, which is that rubber part you can clearly see in your pic at the place where your fill tube goes into the case and that used to look alot like this https://www.autozone.com/external-en...5113/69023_0_0 except now it's split in pieces and all spread-out looking, is ...split in pieces and all spread-out. Might have something to do with it.

Then change out the fill tube seal and see if it fixes it.