Macadoo

This is the TH350 on my '71 CS. I'm not freaking out about it since I've know for a while it was having trouble. But here's the deal:

The trans runs fine, shifts fine, feels fine, unless I let the car idle in park or neutral for more than, say, 60 seconds. If I do, the trans won't kick into Drive. It will go into reverse, but not drive. I can sit for ten minutes holding the brake with the car in drive and it will run fine. It only happens if I let it idle in park or neutral, and if I do, I have to let it sit (cool?) for about 15 minutes. The fluid has a definite brown tinge but doesn't smell burnt. I did a complete fluid and filter change about 25k miles ago (two years ago) when I pulled the motor. Downshift cable seems to be working fine, not sticking anymore. I've been driving the car like this for weeks (when it isn't friggin' raining) with no problems.
Oh, and yes, the fluid level is right at the "full" mark.
Thoughts?

rjohnson442

If you hit the gas while in drive will it "kick" into drive? whats your idle RPM in drive?

droldsmorland

Read the line pressures when its doing this. Low psi=bad pump. A tell-tale is if it kicks into drive when giving it RPMs, I think thats what rjohnson is eluding to?

Octania

filter and new juice cannot possibly hurt

Macadoo

Hmm, I don't currently have a way to test the line pressure but I can certainly rev it some. Just as a wild guess, at what RPM should it kick in?
It idles high because of the AC; meaning I have it set high. Maybe 800. I'll check.

Macadoo

Okay, well, hmmm. Now it won't do it. Meaning it won't NOT go into drive. I drove it around until it reached operating temp (we have a heat index of 110* today), parked it in the drive, let it idle for about ten minutes, then went right into drive.
If it ever does it again, which I'm sure it will, I'll giver 'er the gas and see what happens.

mfpm7232

I have the exact same problem with my TH350 as well. It behaves perfectly until it gets up to operating temps and more pronounced after a long drive or a very hot day.

If moved to park (gas station) or neutral, it simply won't engage into drive without a 15+ minute cool-down. Also when hot I've noticed that it slips when gently accelerating away from a stop. It takes about a half-second for the rpm's to climb and then it kicks in.

After shifting to park or neutral and back to drive, I have tried to step on the gas just a tiny bit to see if I can coax it into gear - no luck.

It's behaved like this for the past couple of summers so I can only expect it will flat out fail at some point. Earlier on I had the fluid and filter changed with no improvement at all. At this point I've been shopping for a replacement or overhaul.

I'm curious to see how things pan out for you. Good luck!
Mark

Macadoo

Sorry to hear that, Mark, but nice to know I'm not the only one. Although I don't have the slippage problem. At least, not yet.

coppercutlass

Have you tried manually putting in 1 vs. D ? The way fluid is passed through the passages is diffrent when in manual low vs. Drive range.

Macadoo

Yeah Copper, I should have mentioned that. When it was having trouble it was the same in all forward gears; 1st, Super, and Drive.

Like I said, I'm not too worried since I have you to help me with that 200-4r install next summer, lol. (When I can afford it).

coppercutlass

So checking the line pressure is easy. There are 3 pipe plugs that cover the pressure taps
They are on the side of the trans where the cooler lines are. The one furthest to the back is the pressure tap , the middle one is the 1-2 pressure tap and the one closes to the front is the 2-3 tap . Tool is 50 bucks. If line pressure was the issue you should get slippage as fluid pressure is how pressure is applied to the clutches. There are some small filters in the valve body perhaps they are clogged ? Transmission fluid expands when hot. So once it thickens up it probably makes clogs worse.

http://www.autobodytoolmart.com/gear...FQiNaQod1r0Lvw

oldcutlass

If the fluid is turning brown, the trans is starting to have issues. You may want to start thinking about that swap soon.

coppercutlass

Brown transfluid is not always really bad. It could just be really old transfluid which over time will also get thin and protect less and as the trans wears it will change color. Engine oil gets burnt and turns darker in a matter of a few thousand miles and will only get more burnt and protect less as it wears out . The th350 that's in my dads pontiac was the one I pulled from my 72when I first got it. The fluid was brown and smelled burnt. I had a trans shop put in all new seals internal and external and I added all new fluid and she is running great . Ran good when in my car but how old it was was anyones guess . It did have a shift kit so someone was in there before.

Macadoo

Well it won't be that long before I have to park it for the winter so I"m hoping it will get me that far. As for the brown-ish fluid, it's only got about 25k on it so yeah, there's some overheating going on. Now, I didn't empty the TC while I had it out and I'm sure there was some old fluid that remained in the trans when I changed it and the filter.

Again, I'm not necessarily looking for a fix. I was mostly just curious. I do find it interesting that I can drive all day without a problem unless I idle in park/neutral. It does sound like a clog or something sticking when the fluid heats up.

coppercutlass

You know you could put some seafoam in the trans . Anywho once you do your swap which I will be glad to help you with I want your th350 to tear into it. Its hard to come by an untouched trans yours seems original enough lol my reason is I wanna see what the factory did. I have a few cores here and all have had monkeys in them.

Macadoo

I assumed that would be the price of helping me. Gonna' haul that back home on the train, are ya? ;-)