350 transmission

[WolverineStepside]

Have you verified the tranny fluid level is full while warm and level? Bogging down might actually be slipping out of gear which would happen more at low RPMs vs higher. Good luck.

 

[rt66paul]

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/

Can't we call detente over the detent issue? Why can't we all get along?

 

[MikeB]

A couple things: Back in the early nineties, I had a TH350C in an 81 C10 that would shift into 3rd gear and lock-up the T/C immediately, even at very low speeds. With its 2.56 rear end (!) the revs must have dropped to 600 RPM or so, and the entire truck would shudder! So I essentially had to keep it in 2nd gear unless I was on the highway. I don't remember the exact fix, but the trans repair shop set it up so it would lock-up only when I flipped a switch, which I did only at highway speeds.

On another note, my 69 C10 had a TH350 that did the 1-2 and 2-3 shifts very early, even at full throttle. That was cured by an adjustable modulator with the adjuster turned CW a few turns more than as delivered.

 

[Jrgunn5150]

To the OP, what happens if you shift manually?

 

[JON79C10]

Ok professional trans builder here....

Lets cut through the myths here....The detent/kickdown/passing gear cable does not control fluid pressure from throttle position on a TH350. Fluid pressure for engine load and road speed are adjusted/monitored by the Modulator and the Governor. The 700R4 has a cable for fluid pressure which combines both engine load and kickdown because it has no modular, it still has the governor looking at road speed. The cable on a TH350 only controls kicking down to the lower gear at nearly full throttle. Most of the cable is slack right up until the down shift point so it cannot be responsible for partial throttle fluid pressure. My money is with Mike B - adjust the modulator for later shift. And be sure that vacuum for the modulator is taken direct from a good manifold source - not a ported vacuum source on the carb. Make sure all vacuum pipes are strong and air tight. Too soft and they will squidge shut.

 

[Jrgunn5150]

My money is with Mike B - adjust the modulator for later shift.

This is why I asked what happens when manually shifted, I expect modulator isn't adjusted correctly as well.

 

[Randy Terry]

Okay, this is what I found and it helped a lot put on the new module and adjusted screw clockwise and clean governor. Shifts a lot better now . Thanks for everyone's advice and knowledge.

 

[HotRodPC]

Whew !!! We made it through this one !!! And THANK GAWD !!! It had not a damn thing to do with the DETENT cable, Kickdown Cable for those who believe that. That whole argument just makes me miss my Th350's. Now I want one back in one of my trucks.

 

[MikeB]

Whew !!! We made it through this one !!! And THANK GAWD !!! It had not a damn thing to do with the DETENT cable, Kickdown Cable for those who believe that. That whole argument just makes me miss my Th350's. Now I want one back in one of my trucks.

I've had three of them over the years, and they've always served me well. That even goes for the "C" after the lockup problem was resolved. The trans in the 69 pickup I mentioned above was rebuilt sometime around 1990, and then had some seals replaced around 2012, but it's still working perfectly. That one and my current truck's trans have a Trans-Go 350-1 shift kit, which makes shifts a little firmer (not bone-jarring by any means), and I hear it helps with clutch longevity. Jon, is that correct?

 

[Jrgunn5150]

I've had three of them over the years, and they've always served me well. That even goes for the "C" after the lockup problem was resolved. The trans in the 69 pickup I mentioned above was rebuilt sometime around 1990, and then had some seals replaced around 2012, but it's still working perfectly. That one and my current truck's trans have a Trans-Go 350-1 shift kit, which makes shifts a little firmer (not bone-jarring by any means), and I hear it helps with clutch longevity. Jon, is that correct?

They always claim a quicker shift=less wear on the clutches. The logic is sound, but there's really no way to verify it.

My personal favorite, and I won't build a GM without dual feeding the direct. The Transgo kits all dual feed via Valvebody spacers. For the 90% of people 90% of the time they work great.

You can dual feed them all internally with a few modifications, but to the guy his his driveway, they work fine.

 

[HotRodPC]

A stage 1 kit is considered an RV/Towing kit. It does increase clutch longevity by making the shift a bit quicker and firmer. More of what I'd call a positive shift rather than a slow smooth gradual shift. Stage 2 is considered Street/Strip where the shift can be a hard shift at half or wide open throttle take offs. I never got to wear out a Th350. I always broke them and didn't even give a rats ass. When I finally got the dogbone element intermediate sprag, I quit breaking those, then it was input shafts. Got a hardened input shaft and that fixed that for the most part but then the shaft would hold up and it would break out of the drum. Usually at least once a year to year and a half I'd break one. That was after I finally quit breaking driveshafts and rear axles with the Muncie 4 speeds. It cost money to play hard, but I damn sure wasn't doing a Turbo 400. I would now days though, only cuz I'm much older and don't want to be wrenching near as much as I did back in those days.

 

[73c20jim]

Switched carbs from Eddy 1405 to rebuilt Q jet. TH350 kickdown worked fine with Eddy, now not with Q jet. Lots of information to adjust it.

My question is how???

 

[Matt69olds]

As stated previously, the DETENT cable (what GM has called the cable to command a WOt downshift since the TH350’can out in 1971) has zero effect on line pressure or shift firmness. The detent cable should bottom out in its travel at about WOT. If the trans in the 85 truck is original, I’m almost positive it will be a TH350C (lock up torque converter) I bet you will find a 4 pin connector on the drivers side of the case, just above the pan rail.

The vacuum MODULATOR should have a red stripe around the barrel. The modulator with a black strip is for diesel applications I believe. You can adjust shift points a few mph up or down by turning the setscrew inside the neck of the vabuum fitting. About 4-5 is all it will go, any more will damage it.

Lastly, the TH350 will handle 550-600hp properly built. As stated previously, the intermediate sprag is the weak link. Unfortunately, it can’t be upgraded cheaply like the early 400 can. Special drums with sprags from the Ford E4OD are available in the aftermarket, but they are expensive, about 550 bucks. Any 400 trans in good shape with a cheap shift kit will handle much more than a 350. Therr are things that can be done during a overhaul that will improve durability, , but other than valve body modification that’s all that can be done without transmission removal.