My 700r4 and the aftermarket torque converter lockup kit

[Fishinfool]

So I had my transmission rebuilt and I got it back and in less then ten miles it burnt up the torque converter and the guy rebuilt it again and the same thing happened he’s having a hard time figuring out what exactly is going on and my next question is I put an aftermarket torque lockup kit on it and when it locks up it won’t accelerate , actually it won’t do anything unless the pedal
Is mashed all the way to the floor it’s a 700r4 with a 383 stroker and it has the sniper 2 injection system any help would be greatly appreciated

 

[Wes Harden]

Does it stall at stops ?
How Many gears is the lock up doing? Just 4th? Or 2nd and 3rd.
Who's lock up kit did you use?

 

[Fishinfool]

It locks up at 50ish mph and it’s a KNM it only acts up like I described when it’s in 4 th and it does not stall

 

[Wes Harden]

That sounds about right, do you know what the converter stall is? Is the link up delayed any ? And finally what rpm is 50mph

 

[Fishinfool]

That sounds about right, do you know what the converter stall is? Is the link up delayed any ? And finally what rpm is 50mp

 

[Fishinfool]

The stall is 2400 and the rpm’s at 50 mph is about 1100 rpm’s it’s got 308 gears which are in the process of getting different gears

 

[Fishinfool]

That sounds about right, do you know what the converter stall is? Is the link up delayed any ? And finally what rpm is 50mph

I don’t know if the lock up is delayed I don’t think so

 

[Wes Harden]

So this where the problem is the 50 mph speed is so low in rpm that the engine is not making any power. My math says you have 33" tires.
My Heavy ass k20 burb has 33's and 4.88 ring n pinion, at 50 mph in 4th I am at 1800ish rpm, can't accelerate on any kind of grade over 1%. Have to down shift into 3rd.
As for burning up the torque converter clutch, I can only guess, possibly to much heat in the trans. My TC has over 20k fairly hard miles on it. My set up locks the tc as soon as it shifts into 4th, a slight delay would help the engine make a bit more power before lock up. I am considering adding a vacuum delay switch to mine.

What gears do you have in mind ? With the better torque curve of a 383 and lighter K5, you should be a little better off

 

[Fishinfool]

I’m having 488’s built right now they should be done by the end of the week and I’m runnin 35’s

So this where the problem is the 50 mph speed is so low in rpm that the engine is not making any power. My math says you have 33" tires.
My Heavy ass k20 burb has 33's and 4.88 ring n pinion, at 50 mph in 4th I am at 1800ish rpm accelerate on any kind of grade over 1%. Have to down shift into 3rd.
As for burning up the torque converter clutch, I can only guess, possibly to much heat in the trans. My TC has over 20k fairly hard miles on it. My set up locks the tc as soon as it shifts into 4th, a slight delay would help the engine make a bit more power before lock up. I am considering adding a vacuum delay switch to mine.

What gears do you have in mind ? With the better torque curve of a 383 and lighter K5, you should be a little better off

thNks f

 

[Fishinfool]

Thanks for the input I was hoping that the gears would help

 

[Wes Harden]

they will, hopefully the 383 and less weight than my set up, 355 and 7k plus big girl will help, I really don't like my 4th gear performance till about 75 mph, were my engine is really starting to make power at 2500 rpm.
My cure with either be a 454 or 5.33 which end up 3.73 in 4th. 5.33 bring different issues, like shifting from 1st to 2nd at 6-7 mph. As mine stands it shifts at 9-10 mph, lite throttle I can be in 4th by 42 mph.

Get a big external trans cooler, try to keep the pan temps under 190°

 

[gmbellew]

I don't switch from D to OD until steadily above 55mph in my burb with 350TBI, 700R4, 3.73 gears, and tires that tape out a hair more than 31.5" (33x10.5xr15). too low of RPM and 3/4 shifting and TCC lock/unlock otherwise.

 

[Stephen]

The 700 does tend to reward some driver control for sure. Don't be afraid to use that shifter and some manual control of the convertor is usually a good idea too. Along with this comes a trans temp gauge and paying attention to it. And the 700 LOVES deep gears and good torque from the engine. Which was often a problem in it's native homes.

 

[Blue85]

The standard clutch in a 700 TC isn't very beefy. Adding higher stall adds a lot of heat/wear while locking up. In a standard setup you'd have like 1800 stall and by the time you're at highway speed, there is only a couple hundred RPM of slip when the converter goes to lock (from tapping the brake I suspect it's even less). Going to a higher stall, with the wrong gears, there's likely to be a lot of slip when the lockup happens. If the engine noticeably moves in the torque curve, that can be your evidence. My guess is that you'd need some modifications to apply lockup oil more quickly to make it live, but this is just a hunch.

My only experience is that when I rebuilt my 700 back in 2000, I used a remanufactured Corvette converter. I hated the higher stall and the clutch in it failed in a few months' time. When I went for another converter, they recommended a "heavy duty clutch". I have no idea what's different, but since it's still running 23 years later I guess it's better.

Thinking on this more, I wonder if you can use the converter from a 2000's 4L60, that is setup for the PWM modulated lockup. Those are a tougher material designed to slip.