'69 C/10 Stalling Issues - TorqueConverter?

[clarlee]

I've been working on a 1969 Chevy C/10 with a LG 250 engine and a THM350 automatic Trans. I'm having issues with it stalling out while driving. I can hit the gas and go, but when it gets to about 40-45 ish MPH, it starts dragging (almost feels like your downshifting) and will eventually stall if you don't let off the gas and slow down a bit. If you slow down to about 30-35 MPH you can hit the gas again up to the same 40-45 MPH and the same thing happens all over again. Just to get more info, I took it to a nice straight downhill grade and can get it to accelerate to more than 45 when going downhill.

It has also been wanting to stall while slowing/stopping. Note, I can throw it in reverse/neutral/park and haven't been able to get it to stall, I'm only having these issues going forward. It also doesn't matter if I'm in drive or 2nd. This problem is definitely speed related and not engine RPM related.

I am assuming that it's a bad torque converter. I am not noticing any odd sounds, vibrations or other weird things coming from the motor/trans, so I don't think the problem is there, but I'm more of an engine guy, I don't know as much about transmissions.

Any ideas would be greatly appreciated. I've already pulled the trans out. I'm not against buying a new TC, but I don't want to if that's not going to fix the problem.

I first posted about this here:
http://www.hotrodders.com/forum/69-c-10-stalling-issues-torqueconverter-234944.html
It has some discussion already. May help...

Thanks in advance

[Odaroloc]

Im no expert by any means as i am only 16 but I am learning and really want one of these old trucks! Does it have an inline fuel filter? We recently moved from Kansas to Alaska and our RV has a 1983 454 in it and it was doing the same thing. Only got to about 40 then started to die. We replaced the inline fuel filter about 7-9 times and found out that there is a lot of rust in the gas tank and the filter was getting clogged. Once we replaced it, it was fine for a few hundred miles and we could get up to 70-75 and then it would clog up again and we would be back down to 40. Not sure if this helps or not but i figured it couldn't hurt. Hope you find the problem.

Mike

[clarlee]

The filter is good. I replaced the tank and lines not too long ago. The filter itself is also only about two months old.

[Odaroloc]

Well im sorry then, I dont have that much knowledge yet to be able to help you. I hope you get this figured out.

Mike

[Xeen]

You have provided very little information on what you have and haven't done to the engine so here's what I recommend.
You need to check the compression on all cylinders first and foremost.
There is a really good chance that the camshaft and entire valve train is pretty worn at 150k miles, you are probably floating valves left and right.
Have you rebuilt the carburetor since you have owned it.
I would pull out the gas tank and have it hot tanked, don't put the old fuel back in it afterwords.
I would also rebuild or change out the distributor, replace the timing chain and gears and then put a timing light on it and calibrate it properly.
I would also change out the plugs and install NGK G-power platinums.
You also need to completely go through the vacuum system and replace everything.
You also need to buy some spark plug wire seperaters and heat shields and organize them to keep them away from your exhaust manifold.
You need to basically completely go through the entire engine and troubleshoot it and recondition it and bring it back from the dead, it is very old and needs some serious attention.

[clarlee]

Originally Posted by Xeen

You have provided very little information on what you have and haven't done to the engine so here's what I recommend.
You need to check the compression on all cylinders first and foremost.
There is a really good chance that the camshaft and entire valve train is pretty worn at 150k miles, you are probably floating valves left and right.
Have you rebuilt the carburetor since you have owned it.
I would pull out the gas tank and have it hot tanked, don't put the old fuel back in it afterwords.
I would also rebuild or change out the distributor, replace the timing chain and gears and then put a timing light on it and calibrate it properly.
I would also change out the plugs and install NGK G-power platinums.
You also need to completely go through the vacuum system and replace everything.
You also need to buy some spark plug wire seperaters and heat shields and organize them to keep them away from your exhaust manifold.
You need to basically completely go through the entire engine and troubleshoot it and recondition it and bring it back from the dead, it is very old and needs some serious attention.

Just to go through the list:

-I made sure compression was good when I replaced all the engine seals
-I haven't taken a look at the camshaft
-The carb has been rebuilt, I want to say 5-ish years ago (hasn't been driven much so not too many miles on the rebuilt carb)
-Do you think it is necessary to do anything to the gas tank since it's only a couple of years old?
-I haven't done any work on the distributor, but the plugs and wires are fairly new. None of the wires run past the exhaust manifold
-I have gone through the vacuum system and checked for leaks. I didn't find any, but haven't replaces EVERYTHING

When I was resurrecting the engine from total death, I went through a bit to get it running again.

Let me ask this, everything looks/feels/sounds right under the hood. If the problem is indeed engine related, why would everything act normal until I put it in gear and get up to speed. Not trying to sound snarky, I'm seriously asking out of curiosity.

[Xeen]

All this new information is helpfull, this is stuff we needed to know to help you diagnose the problem.
I'm like you I'm not a transmission guy so I really can't tell you if a faulty torque converter can cause the issues you are reporting.
With your description of the work you have done on the engine some of the guys might have more ideas for you.
It is curious that the problem only presents itself at 45 MPH, I am not a expert engine mechanic so I can only offer limited help, however an experienced old school mechanic should have a very good idea what the problem is after a single test drive, like the mechanic Wayne Carini has on Chasing classic cars.

[clarlee]

I also find it weird. I dont know wwhy I never checked, but when I turn the spindles on the trans, it sounds normal, but after I put the tc on and rotate the tc on the trans, it whines a bit. Its not bad, but its there.

[clarlee]

I think I'm going to just replace the TC. If I'm wrong, it can't hurt to have a new one on there. The priciest one I can find is only $350-ish, could be worse.

I've narrowed it down to three that are compatible with my trans:

B & M Torque Converter, Holeshot 2000 Series - 1900 - 2100 rpm

B & M Torque Converter, Tork Master 3000 Series - 2800 - 3200 rpm

B & M Tork Master 2000 Torque Converter - 1900 - 2100 rpm

B & M Torque Converter, Tork Master Series 2400 - 2300 - 2500 rpm


Which one seems logical. I get the concept behind the stall speeds, but don't know which is the best fit for my truck.

[Xeen]

I would Imagine you can get a stock style torque converter for pretty cheap, I don't see any reason to go buy an expensive aftermarket converter because there isn't going to be any advantage to it.
Check this one out.
http://www.ebay.com/itm/Summit-Racin...aec416&vxp=mtr

[clarlee]

I got this one: B & M Torque Converter, Holeshot 2000 Series - 1900 - 2100 rpm

I got everything replaced and now nothing happens. I'll shift into any gear, and either idle or floor it, and I don't move an inch. I've rechecked everything to see if I could have missed something, but everything seems to check out.

I REALLY don't want to take that trans out any more than I have too, but I'm out of ideas on this one.