hookem horns

New problem just developed. The TH350 in my 69 Cutlass is not shifting into 3rd when in Drive. 1st to 2nd shift seems ok, then revs build and will not go into third. I can move the shift lever down to 2nd (S) and then back to drive a get it to shift. Once in 3rd, drives normally with no slipping. It started right after I did some maintenance and changed the plug wires, so checked to see if I knocked off the modulator hose but it looks fine top & bottom. Not seeing any fuild being sucked up the line either. Fluid level is OK and also made sure the kickdown cable was moving freely.

The previous owner had a supposedly freshly rebuilt TH350 put in a few years ago as a swap for the original jet-away. Have the receipts but that shop is 200 miles away. Maybe 10k on it since then and never had any issues until this popped up. Any ideas? Never done any trans work but suppose I could pull the govenor. May give up and go to a shop after that.

droldsmorland

Do you have the steel line running from the intake down to the modulator? If so check it for obstruction. A bad modulator will cause 2-3 bump slip shift or a rough up shift not a no shift. But the fact that you can force it into 3rd and it runs ok once in 3rd Id start with the modulator and its line(s). Cheap & quick. A vac leak will cause delayed up shifts. Check all this first as it sounds like the problem occurred after you were messing around under the hood.
Next verify the linkage is actually going into drive both at the shifter and in the trans. Verify that with the pan off looking at the manual shift linkage.
Next is a pressure check. This is the only way to check the health of your hydraulic pump(aka Auto trans). Verify all the correct pressures are in spec in all gear selections per the book. This is how you isolate the problem circuit.
Ive seen this same symptom before, it was the 2-3 shift control valve sticking.
The pressure readings will dictate if its time for a tear down. Low pressure readings in 3rd point at the pump hub-direct clutch seals and the direct clutch piston seals. The pressure check will tell you which way to go if that's the case. Hopefully its just modulator trouble.

hookem horns

Thanks and checked that air will flow through the modulator line. A new modulator is pretty easy & cheap, so think it's worth swapping? Could drop the pan but not looking forward to swimming in the fluid, plus not sure if I would know what to check or do beyond the filter. May end up letting a pro do that, as much as I prefer to do my own work.

droldsmorland

Fluid will come out from there too. Jack the car up opposite the direction of fluid flow. It will help somewhat. Just have to swap it out/in quickly. If you drop the pan leave a couple of the front or rear bolts in the pan rail. Leave them lose, support and lower the pan slowly using the left in bolts as a hinge, it reduces the fluid bath. Careful dont bend the pan by letting it drop with the weight of the fluid. Consider instating a drain plug kit in the existing pan or purchasing a new pan with the drain plug. Makes the next trans service much easier.

oldcutlass

If its a T350, make sure your detent cable is not stuck in passing gear. It runs from either the gas pedal or the carburetor linkage to the transmission.

hookem horns

Broke down and took the car to a shop I trust, and it is not pretty. Intermediate sprag broke along with related collateral damge. So much for being something easy/cheap .

Professur

Might be time to upgrade to that 200-r4

coppercutlass

the intermediate sprag is cheap. About 80 bucks or so for an hd one. As long as your clutches are in good shape I would just have them do new seals , the sprag. Clean the case . If you pull the trans it should not be more than 3 hrs. Local shop here charges 250 for labor on a bench job. To remove and install then it gets expensive. Guys have broken the sprags at the track with not much collateral damage . I have a stock sprag and race here if you want it.

Fun71

I am not one of them. When the sprag in my trans went, it took out the drum and clutches.

coppercutlass

Depends how bad it went I guess. Some guys have had it happen and it took out the drum and clutches and some not. I guess its just the way it gives out and use or luck I guess lol. *edit* I meant guys have had the sprag go at the track . Damn auto correct on my phone lol.

droldsmorland

IMO if its apart just do it all. All the consumables. Upgraded "red" frictions, steels, upgraded band, all seals, all bearings, pump etc. Use heavier direct clutch return & pressure relief springs and an HD planetary...etc you get the deal. Planetaries are the weak link in a TH350.
Whats the sense of trying to save a couple hundred bucks verses piece of mind that its all fresh and will be durable for may years.
Now is the time to upgrade as well. Any hard parts as mentioned etc... Other improvements to ponder are... installation of a Trans Go shift improver kit with the Trans Go patented separator/transfer plate. Upgrade the modulator and install a cooler(properly routing the inlet/outlet, ask if in doubt).
Consider a new pan with the drain plug or install a plug kit in the existing pan. It will make fluid changes a pleasure (almost). Also consider running TCI synthetic (clear) trans fluid from the get-go.
IMO A trans does have a break-in period. Change the fluid & filter at about 500-1000mi then every 20-25K for normal driving much sooner if it sees any track duty.

hookem horns

Yes, going this route. A little more on parts is worth it since I'm paying to have the work done and don't want to ever do it again. Wish I had the time & skills to do it myself but never been any deeper into a transmission than a fluid/filter change.

Hindsight is 20/20. Should have dropped the pan myself and would have seen the resulting debris, then could have decided to buy a built 350 or 200-4R instead.

Professur

I'd look at picking up a spare cheap during the summer and taking a stab at it in your free time. They can be had cheap if you're not picky or pressed for time. It being a spare means you can take as long as you like (just not on the dining room table) and the 'special tools' necessary can be home built out of scrap with little more than a grinder and a drill. They're disgustingly simple inside, for all that they're treated as black boxes by most mechanics. Diagnostic tools are as simple as a good runout guage, feelers, and a high pressure guage.

coppercutlass

X2 on rebuilding it yourself. Its no very hard at all. I did some research and many guys in the 11's have ran the th350 with just an upgraded sprag and race , center support from a 700r4 adding more clutches and the trans go shift improver kit. In the 450 hp range these upgrades should be considered. The th350 that's in my cutlass now I built . All I did was add extra clutches in the direct and forward drums and a b&m shift kit . I want to see what it can handle. The th350 I'm currently building is getting the upgraded sprag and race , the 700r4 center support , the trans go shift kit . To build the trans I'm building now is costing me in the 325 range minus converter. Buy the ron sessions book on the th350 best 25 bucks you will spend. As for the clutches the red alto's are great. If you want the best of the best the raybestos blue with kolene steels are the way to go. I have a local trans builder here who gives me advice and he belives based on his experience the borg warner paper clutches are still good up to the 450 hp range. Of course it comes down to prefrence and money use etc etc.