Transmission causing engine to stop running
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
Transmission causing engine to stop running
Car: 74 Vette 350 with TH400 transmission.
Recently we took the transmission out to replace flexplate and torque converter. Both were stock replacment pieces. We took the car out and it ran great, but after about 20-30 minutes worth of driving, the car wants to die. After letting the transmission and engine completely cool, it starts right up and drives with no problem until the transmission gets hot. Engine coolant temps are normal.
It seems that the transmission is getting hot causing the engine to stall and the car doesn't want to move. There is plenty of fluid in the transmission, all lines are hooked up correctly. So far we have taken the transmission out of the car and was wondering what are some internal findings we should look for and replace? Thank you in advance.
/Lee
Recently we took the transmission out to replace flexplate and torque converter. Both were stock replacment pieces. We took the car out and it ran great, but after about 20-30 minutes worth of driving, the car wants to die. After letting the transmission and engine completely cool, it starts right up and drives with no problem until the transmission gets hot. Engine coolant temps are normal.
It seems that the transmission is getting hot causing the engine to stall and the car doesn't want to move. There is plenty of fluid in the transmission, all lines are hooked up correctly. So far we have taken the transmission out of the car and was wondering what are some internal findings we should look for and replace? Thank you in advance.
/Lee
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,113
From: Crossville TN
Are you certain that you removed the plastic caps from the oil cooler "IN" and "OUT" holes. Sometimes they get shoved into the hole by accident. If they are not removed, the blockage will keep adequate oil from circulating.
Also, can you double-check that you received the correct converter and flex plate for your vehicle/transmission. They look so much alike, that someone could 'pick' the wrong one. Call the supplier to see if their records show you got the right parts. If the converter drive hub is wrong for your tranny, it could be putting a lot of side pressure on the pump gear which would generate a lot of heat...and wear!
Also, can you double-check that you received the correct converter and flex plate for your vehicle/transmission. They look so much alike, that someone could 'pick' the wrong one. Call the supplier to see if their records show you got the right parts. If the converter drive hub is wrong for your tranny, it could be putting a lot of side pressure on the pump gear which would generate a lot of heat...and wear!
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
Are you certain that you removed the plastic caps from the oil cooler "IN" and "OUT" holes. Sometimes they get shoved into the hole by accident. If they are not removed, the blockage will keep adequate oil from circulating.
Also, can you double-check that you received the correct converter and flex plate for your vehicle/transmission. They look so much alike, that someone could 'pick' the wrong one. Call the supplier to see if their records show you got the right parts. If the converter drive hub is wrong for your tranny, it could be putting a lot of side pressure on the pump gear which would generate a lot of heat...and wear!
Also, can you double-check that you received the correct converter and flex plate for your vehicle/transmission. They look so much alike, that someone could 'pick' the wrong one. Call the supplier to see if their records show you got the right parts. If the converter drive hub is wrong for your tranny, it could be putting a lot of side pressure on the pump gear which would generate a lot of heat...and wear!
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
Your in park idling and the car stalls out after a 30 minute drive and your first thought is the transmission you just worked on ? I can not even imagine how this is transmission related simply because if it could stall a motor you would have serious drive ability issues way before a 30 minute run.
I wonder if when you pulled tranny you let the motor lean back and cracked the dist cap or when you bolted it back in if you pinched a wire of some sort between motor and bell housing ..
I wonder if when you pulled tranny you let the motor lean back and cracked the dist cap or when you bolted it back in if you pinched a wire of some sort between motor and bell housing ..
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
No fluid coming from any vacuum lines and car is not flooding.
Yes it has spark and starter turns the motor over, but it won't hold idle once it runs. If I leave for a few hours to let it cool, it starts up and runs fine, then after about a 20 minute drive, it starts to stall.
Your in park idling and the car stalls out after a 30 minute drive and your first thought is the transmission you just worked on ? I can not even imagine how this is transmission related simply because if it could stall a motor you would have serious drive ability issues way before a 30 minute run.
I wonder if when you pulled tranny you let the motor lean back and cracked the dist cap or when you bolted it back in if you pinched a wire of some sort between motor and bell housing ..
I wonder if when you pulled tranny you let the motor lean back and cracked the dist cap or when you bolted it back in if you pinched a wire of some sort between motor and bell housing ..
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Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
How do you know the trans is getting hot ?.
When you say it dies after 30 mins. are you talking in park and drive ?
I assumed you checked the butterfly on the carb and its opening up after it warms up ?. You can bump up your idle speed and see if it still dies after 30 mins. I would also check your timing, make sure you didnt move the distributor. Also check your vacuum line going to your tranny make sure its not leaking. They could have given you the wrong torque converter with too low of a stall or maybe has the lockup on it and its killing the engine maybe.
When you say it dies after 30 mins. are you talking in park and drive ?
I assumed you checked the butterfly on the carb and its opening up after it warms up ?. You can bump up your idle speed and see if it still dies after 30 mins. I would also check your timing, make sure you didnt move the distributor. Also check your vacuum line going to your tranny make sure its not leaking. They could have given you the wrong torque converter with too low of a stall or maybe has the lockup on it and its killing the engine maybe.
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
How do you know the trans is getting hot ?.
When you say it dies after 30 mins. are you talking in park and drive ?
I assumed you checked the butterfly on the carb and its opening up after it warms up ?. You can bump up your idle speed and see if it still dies after 30 mins. I would also check your timing, make sure you didnt move the distributor. Also check your vacuum line going to your tranny make sure its not leaking. They could have given you the wrong torque converter with too low of a stall or maybe has the lockup on it and its killing the engine maybe.
When you say it dies after 30 mins. are you talking in park and drive ?
I assumed you checked the butterfly on the carb and its opening up after it warms up ?. You can bump up your idle speed and see if it still dies after 30 mins. I would also check your timing, make sure you didnt move the distributor. Also check your vacuum line going to your tranny make sure its not leaking. They could have given you the wrong torque converter with too low of a stall or maybe has the lockup on it and its killing the engine maybe.
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
What is the difference between idle speed when it's cold in park or neutral compared to when it's hot? And then when it's in a drive gear? At a 700 RPM idle, I can't see anything internal in the trans causing any problems unless there's a fluid leak that's engaging forward and reverse at the same time, but that would be kind of "out there". Especially since it drives normally before it gets hot.
Thread Starter
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
What is the difference between idle speed when it's cold in park or neutral compared to when it's hot? And then when it's in a drive gear? At a 700 RPM idle, I can't see anything internal in the trans causing any problems unless there's a fluid leak that's engaging forward and reverse at the same time, but that would be kind of "out there". Especially since it drives normally before it gets hot.
Very strange and will keep everyone updated.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
If you take a pair of long snap ring pliers and reach down into the convertor you can use them to grab the stator in there. IT should turn one way and not the other. That one way clutch in there is what drives the input shaft.
Another thought- is the front of your convertor flat or rounded? (picture?) If the vendor sold you a convertor made for a 350C it is possible it could be locking up when it's hot and killing the engine. And a convertor for a 350 will fit a 400 no problem. IT's a poor man's stall convertor.
Another thought- is the front of your convertor flat or rounded? (picture?) If the vendor sold you a convertor made for a 350C it is possible it could be locking up when it's hot and killing the engine. And a convertor for a 350 will fit a 400 no problem. IT's a poor man's stall convertor.
Melting Slicks
Joined: Aug 2012
Posts: 2,548
Likes: 379
From: Woodinville WA
you have a low stall torque converter? (I'm betting yes), and it's one that's especially for torque (locks up even sooner).
So here's my guess
your converter is pumping so much fluid (low stall) that the motor needs a higher idle to keep it running.... you said 650 -750 rpm, I presume (there I go again assuming) that is free idle, without it being in gear. In reality that idle should be closer to 900 rpm....
Strangely/coincidentally, I had the same problem with a 2400 stall B&M, to keep the car running, it's free idle had to be 1200. You can also adjust the timing so you have more static advance at idle, but then you'll run into problems with the starter having to overcome that much advance. You can also adjust the idle screws to give it more fuel at idle - the problem with that is it can flood the engine if you give it too much (if you shut it off from idle).....
turn up your idle
So here's my guess
your converter is pumping so much fluid (low stall) that the motor needs a higher idle to keep it running.... you said 650 -750 rpm, I presume (there I go again assuming) that is free idle, without it being in gear. In reality that idle should be closer to 900 rpm....
Strangely/coincidentally, I had the same problem with a 2400 stall B&M, to keep the car running, it's free idle had to be 1200. You can also adjust the timing so you have more static advance at idle, but then you'll run into problems with the starter having to overcome that much advance. You can also adjust the idle screws to give it more fuel at idle - the problem with that is it can flood the engine if you give it too much (if you shut it off from idle).....
turn up your idle
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
The last thing this issue is his transmission or T/Q converter. Nothing inside the trans could cause this and still allow it to drive well as he states , also it is not his t/q converter because it would NOT in any way possible offer a stall speed so low it stalls the motor only when hot after 30 minutes of driving. "And once trans cools down all is well again for 30 minutes " come on really ,, his stalling and not starting until cool , that's a trans issue ??
If he had said it seams to stall only when the clocks second hand passes the 3 on its dial and we just changed the clock .. how many would offer up clock issues to fix his stalling
It is that he just did an R&R on his trans that he is fixated on it , I say check to see if ya cracked dist cap or have a wire issue related to the areas of work performed to remove the trans. For all we know his points are worn ............
If he had said it seams to stall only when the clocks second hand passes the 3 on its dial and we just changed the clock .. how many would offer up clock issues to fix his stalling
It is that he just did an R&R on his trans that he is fixated on it , I say check to see if ya cracked dist cap or have a wire issue related to the areas of work performed to remove the trans. For all we know his points are worn ............
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
I don't remember, does the 400 have a vacuum line going to it like the 350? If so, I'd check to make sure the vacuum line is still attached at the manifold. Sounds like a vacuum problem. When the engine is cold, the choke is closed/partially closed, gets hot, choke's open, but with an open vacuum line....dies.