bobs77vet

what are the tell tale signs of a bad Torque Converter?

does the stall speed increase or decrease?

does it make noises? and if so what kind?

when does it make noises all the time or just when in gear?

MELVINJ

Torque convertors vary rarely " go bad", in average or agressive street driving. The sounds you are decribing, is indeed fron the tranny, could be the planetary gears going bad. Most mechanical noises from a auto tranny are caused by these, the flex plate, loose tranny mounts, or non tranny related sources. As far as rpm loss or gain, I dont beleive a bad converter would cause this

MELVINJ

Torque convertors vary rarely " go bad", in average or agressive street driving. The sounds you are decribing, if indeed from the tranny, could be the planetary gears going bad. Most mechanical noises from a auto tranny are caused by these, the flex plate, loose tranny mounts, or non tranny related sources. As far as rpm loss or gain, I dont beleive a bad converter would cause this

MELVINJ

Sorry, read the ABOVE post by me, not the one prior

45ACP

I used to run a machine shop that rebuilt about 8000 converters/year....

"does the stall speed increase or decrease?"

It would never go down, but it is possible for it to go up before a complete failure.


"does it make noises? and if so what kind?"

It could be a whine or a howl, but it is possible for it to be surprisingly quiet.


"when does it make noises all the time or just when in gear?"

Usually any time the motor is turning over, but not always. It is far more likely to make noise when the car is in gear.

Pull the pan and have a look at the oil. If is is contaminated with steel filings, it is likely that you have a problem.

Get somebody that knows what they are doing to have a look at it. DO NOT drive the car if you suspect that the converter or the tranny is in trouble. If you do, and either is in trouble, you will only cause more damage ($'s).

bobs77vet

thks guys....i have a torque converter that i'm going to be replacing with a higher speed stall torque converter because this one is just too "tight" , seems like the stall speed is at about 1400 rpm. i have noticed that when i put the car in gear i sometimes hear a sound similar to the sound of the speedo cable hitting the trans tunnel, kind of a "drum like" noise... the torque converter came with the 700r4 when i did the trans swap and just isn't matching up nicely with my rebuilt engine...any thoughts on the noise? when i set up the trans i did a pressure check onthe trans system and everything was within specifications for the pressure ranges.

gkull

Listen to 45ACP he knows his trannies and TC's!

this is a problem - "when i did the trans swap and just isn't matching up nicely with my rebuilt engine...any thoughts on the noise?"

ALL GM tc's have a common bolt pattern to the flex plate. It has to mount flush. Pull out the flex plate to TC bolts. The TC should be easy to spin. Sometimes you have toput a pry bar behind the tc and slide it forward to the motor. Never try to use the flex plate bolts to suck the TC forward. You can bend the flex plate doing that.

Another problem I've seen is people putting the flex plate on backwards. That will cause all kinds of odd noises and you would swear that the tranny must be going out.
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"Torque convertors vary rarely " go bad",

I must be unlucky because I've ripped the guts out of all different kinds over the years. I had a B&M hole shot or something like it once in my TH350 and I wanted to see what was wrong and I had a tranny shop cut it in half. The aluminum splined stator had shattered and fed the snap rings and busted chunks through the system. The furnace brazed steel fins were all bent and mangeled.

I had a brand new TCI street fighter and I was going to show my buddy some great burn outs. So I was power brake loading the system and smoking my old 285/35/17 rear tires. About the Fifth 100 yard burn out the TC smoked. I was pissed because it had not even been in the car for three days. They offered to give me a new one I just got my money back and bought a better one

bobs77vet

thks for the info and sorry i sent you in the wrong direction, the fit is fine, what i meant is that the stall speed is not matching up to the Cam i have in the car and that difference in idle speed between being in park and being in gear is about 500 rpm....my current torque converter is too "tight" so the car idling in gear at 850 rpm turns into an idle of 1350 in park and the stall speed is about 1400rpm

gkull

Performance lockup convertors are quite expensive, but they do last a long time. My 9.5 inch is on it's 4th motor and 5 years old. It can handle smoking the tires at 90 mph during a 2-3 shift. It's also done lots of line lock 6000 rpm in second gear at the drag strip with 28X10 GoodYear slicks. So the wheel speed is about 80 mph while your heating up the tires. A stock converter would blow before your tires even got hot.

The guys on the C-4 forum seem to like the Vigilanty & ProTorq 9.5 inchers. They are @$800. I went with Art Carr Racing because they used to be down the street from my office.

The 9.5 inch are only @ half the weight of the stock 11 inch or what ever the 700R4 comes with. So it's like running a light weight flywheel on an manual tranny.

45ACP

Absolutely. The stock converters are actually 12". They weigh 38lbs dry. The reduction in weight makes a big difference, but the reduction in diameter probably makes more. There's a huge difference in the amount of force needed to accelerate the two sizes. That little one will snap up to speed way, way quicker.

gkull

45ACP - I knew that it was big monster that i took off when I blew the first one. 12 inches and 38 pounds. With full of oil it would be in the mid 40's The rotational force would be massive at high rpm like the 7000 rpm I was running my 355 ci motors to back then.

bobs77vet

are there any down sizes to the smaller diameter lock up torque converters in the 2500 stall speed range? i'm running a 350 with approx 350 hp and maybe 400 ft lbs

gkull

The downside to higher stall is heat. Easily overcome with the biggest B&M tranny cooler or do something really trick like the racing Vettes and run the tranny cooler out back somewhere with an electric fan.

The big B&M is setup for 1/2 inch lines. The 700R4 brass tranny fittings for the cooler lines are actually reducers to the 3/8ths size. So I tore out all those stock steel lines going to the radiator and had a shop custom hydraulic crimp SS covered teflon 1/2 inch hoses with ends. They really came out nice and the tranny end has quick disconnects so I can change the tranny out faster.

bobs77vet

cool ideas...is the heat generated only when using it hard or in every day driving? i'm pretty easy on the car and it would not suffer to many gruelling events....i'm not sure i could even bring myself to do a real burn out... i would be thinking too much about my $3K rear end getting screwed up....

45ACP

This is exactly correct. Run a big cooler to chuck the heat into the atmosphere and life will be good.

bobs77vet

you know i have those abandoned AC coils sitting in front of my radiator they probably can hold an extra gallon of fluid....if were to pressure test those for leaks what kind of pressure are we talking about being generated by the 700r4 cooling lines? thks bob