350 transmission

[74 Shortbed]

Sorry for not joining in earlier been a long day at the races.. Man, talk about mass confusion, I'm not even gonna try and figure this **** out, lol, so I'm gonna start with this last post. First off when did this problem start, before or after the Modulator change??, did you get a red stripe?, now after it bogs down does it stay there or does it pick up as rpm goes up??, from your description it seems to me that it just shifts to quick into 3rd(the spread between 2nd and 3rd is way too narrow) and it's the load of 3rd gear pulling the motor down due to lack of rpm and torque, am I close or am I getting this all wrong?.lol. Assuming I'm close here, did you check for vacuum leak to the Modulator?(that can be a cause of early shifts) did you try to adjust it?, did you check the governor to make sure the valve moves smoothly?.. A note on cables, on a 700r it's a TV(throttle valve)cable, it adjusts line pressure from idle to full throttle(low pressure at idle, high pressure open throttle)that's it. On a 350 it is a kick down cable just like a 400 has a kick down switch, they kick down to next lowest gear, if you're in 2nd it kicks down to low, if you're in 3rd it kicks down to 2nd, that is their ONLY function and has nothing to do with anything else, hope that clears it up for those that wonder about it.

 

[HotRodPC]

Uh oh, we have some transmission builder disagreement here. Well handle that in PM.

I don't see him here. But I think I got it all out of him now Art. He had the problem BEFORE he swapped the Vac Mod. Me mentioned he did get some trans fluid out of the vac line too which I don't think had anything to do with this, and couldn't have been much or he'd have noticed burning trans fluid and white smoke.

So yeah, at part and full throttle the transmission works fine. It's only light throttle take offs, it does 1-2 fine then almost immediatly into 3rd and yes, bogs down due to low rpm and torque kinda like skipping a gear would do.

And here I already straightened him out on Ford have kick down cables, let's get terminology right, it's a detent cable, NOT a kickdown cable.

 

[74 Shortbed]

Uh oh, we have some transmission builder disagreement here. Well handle that in PM.

I don't see him here. But I think I got it all out of him now Art. He had the problem BEFORE he swapped the Vac Mod. Me mentioned he did get some trans fluid out of the vac line too which I don't think had anything to do with this, and couldn't have been much or he'd have noticed burning trans fluid and white smoke.

So yeah, at part and full throttle the transmission works fine. It's only light throttle take offs, it does 1-2 fine then almost immediatly into 3rd and yes, bogs down due to low rpm and torque kinda like skipping a gear would do.

And here I already straightened him out on Ford have kick down cables, let's get terminology right, it's a detent cable, NOT a kickdown cable.

Sorry, there's no detent, only detents are on the shift rod, the cable actually works the same principle as the 700, it pushes a plunger in smoothly no detents.. As far as the Ford you need to look at one, it works the same way except they put a lever on the outside that hooks up to a rod, the rod rotates the lever and pushes a plunger inside the tranny, no detents....

 

[HotRodPC]

I get that, but it's name is a detent cable. I promise. I wouldn't make it up or lie. It's been called a detent cable in every GM book I ever looked at in the 80's. You won't be the first I had this disagreement with, and you won't be the 2nd either and I win everytime. I once walked into a Transmission class to take a buddy a trans core for him to work with. Pretty much donated it to the school. I said something about the detent cable being kinked and no good and the instructor immediately turned around and asked if I was a student. I said NO. He said I didn't think so, but noone ever calls that by it's correct name, you're about the 3rd person ever to call it a detent cable and that's exactly what it is.

 

[74 Shortbed]

Still no detent and I will call it what it actually is..... Over and out!!!...

https://www.google.com/search?clien...faAhUQXKwKHV11DDYQ1QIIgwEoAA&biw=1917&bih=923

https://static.summitracing.com/glo...s/LOK-INS0121-TH350-KickdownBracket-Cable.pdf

https://www.autozone.com/transmission-and-drive-train/transmission-kick-down-cable

https://www.summitracing.com/int/se...cable-jacket-material/braided-stainless-steel

http://www.bmracing.com/products/30287-kickdown-throttle-valve-cable-for-gm-th-350-transmission/

 

[HotRodPC]

Alrighty then, call it whatever you wish, but do keep in mind, it does however do more than just kickdown and does more than what a Th400 KICKDOWN Switch does. Without it hooked up, shifts will be very early. I can find just as many links calling it a detent cable as well as instruction manuals.

 

[bucket]

Call it what you want, kickdown, detent, whatever. But I agree, it's adjustment will change kickdown points as well as upshift points, although to a lesser degree.

My first car had a th350 in it and one of the first things I tinkered with was that cable. I'm sure it was right after flipping the air cleaner lid. It had the adjustable slider bracket mounted to the intake. Within the factory adjustability, it would change the upshift points as much as 10 mph or so. I'd imagine if it were unhooked or otherwise faulty, it could really screw with the upshift points.

 

[HotRodPC]

It certainly would. It would shift very early if the cable was disconnected at light or part throttle, and even earlier than you'd like at full throttle. There is such thing called detent pressure which is controlled by the detent valve operated by the detent cable. This can delay upshifts as well as firm up shifts. That's why I love a Th350 over a Th400 all day long. If I don't need brute strength, gimme a Th350 every day. Unlike a Th400 where you have to floor board the throttle to hit the kickdown switch, you can even adjust a detent cable to get downshift at 3/4 throttle if you wish. Granted, that means tightening it up a bit it's likely to delay your shifts as well as make them firm. Just one of the characteristics of a Th350. Powerglide does use a kickdown rod. PG, Th350,T400 and even 700r4 all have different characteristics.

If you ever want to know the nuts and bolts of a Th350, I suggest the Ron Sessions book Th350 handbook. They may be out of print now but they're obvioulsy still available to be bought. I bought one in the last couple months just because I seen what happened to the Th400 Build and Modify by Ron Sesssions. Try to find one of those books new for under $100 these days. I figured it might happen to the Th350 handbook too.

Here's a little of the index to the book with the pages he talks about the detent valve. You can actually view part of the book on Amazon.com using the Look Inside Feature. It's a good one. Probably $18 or so while you can still get them.

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[HotRodPC]

Geez, there' the price to the book right there. It's up to $25 now. Still worthy if you're interested in Th350 transmissions. Seems I got it for $15 just a few months ago. It's probably been longer than I realized. But go ahead, do a search for Ron Sessions Building and Modify Th400 and see the prices if you find it. And they've come down alot in the last year. For awhile it was $150 for a wore out wrinkled up cover one and if it was mint, $200 or more. So if the same happens with the Th350 book, at least you'll have one if you get it soon enough.

 

[bucket]

Speaking of the th400, it will still kickdown without a working kickdown switch, it will just not be as eager to do so. Which reminds me of something else I need to get done on my C10.

 

[rpcraft]

Not picking sides, but these differences of opinion here are why i generally don't trust rebuilders, even if they work in a transmission shop. If it's just a matter of following instructions in a book, vs someones opinion of WTF widget A should be called, I might as well buy the book and do it myself....

 

[bucket]

Not picking sides, but these differences of opinion here are why i generally don't trust rebuilders, even if they work in a transmission shop. If it's just a matter of following instructions in a book, vs someones opinion of WTF widget A should be called, I might as well buy the book and do it myself....

I'm certainly no transmission rebuilder, so you can trust me

Seriously though, I'm no expert on the subject, but what I posted is personal experience.

 

[HotRodPC]

Speaking of the th400, it will still kickdown without a working kickdown switch, it will just not be as eager to do so. Which reminds me of something else I need to get done on my C10.

Not picking sides, but these differences of opinion here are why i generally don't trust rebuilders, even if they work in a transmission shop. If it's just a matter of following instructions in a book, vs someones opinion of WTF widget A should be called, I might as well buy the book and do it myself....

Normally it's healthy for builders to have disagreements and compare notes. But some just won't have it soooo leav'em alone to carry on with what they know. I always keep open minded and have learned some cool tricks, improvisions when needed for like a special tool that you'd need just one or 2 times a year so it's not worth the expense, or mods and upgrades.

 

[HotRodPC]

Back at the ranch.... Something you may also check @Randy Terry is that the cable even has spring tension on it. The detent valve is spring loaded, so you should you be able to pull the cable and feel it spring back. If not, it's either snapped or come disconnected which is rare but I've seen it a couple time for however in the hell it happened because the connecting rod from the cable to the detent valve is hooked nicely on both ends. I have also seen the pin on the lever only be partially on so the lever isn't pushing the valve. Just be sure you feel the spring tension at the carb linkage to verify you're even getting an detent pressure. If not, need to find out if it's a snapped cable, if so and hope it is cuz you don't have to remove the pan to fix it. If the cable isn't snapped but you still don't feel spring pressure pulling on it, then you have to take the pan off to put that assembly back together.

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[Randy Terry]

Thanks, hoping tomorrow I can post what I find out the culprit Maybe.