Understanding my transmission ??

[mikejpss]

As many of you remember I have had problems with my tranny not downshifting into 1st gear. Yesterday evening we pulled the valve body and found a piece of aluminum slag stuck in the first gear valve train.
The tranny mechanic (a friend) that helped me with the endeavor said that I have a "lock-up" convertor and did his best to explain it to me, think I got it.
Question for the day is this:The lockup portion of my tranny is electronically disconnected, obvious as the 4 prong plug wire is missing from the tranny. How will this effect the stock performance of the car (assuming the tranny runs correctly when we put it back together today).
His explanation of the lock-up is that it was designed to give an additional 0.3 mpg, almost like a 4th speed. Havent felt it b/c it was disconnected, do not want to reconnect since the carb and distr. have been changed to a non computerized ones.
Any insight to help me better understand this would be greatly appreciated.
Thanks,

 

[81 Corvette]

I don't know all the particulars, but the torque conveter was designed to "lock up" once the engine reached a set rpm. assuming you were in 3rd (1:1), for every reveloution of the motor, your transmission would turn the drive shaft one reveloution. The rest of time it acts like any other torque converter. With it not locking, you won't get as good of performance in the top end.

 

[mikejpss]

Thanks 81

Would anyone know just what is lost in performance without the lockup? Could it be seen in loss of mpg?
I assume it would be like a standard torque convertor if it does not lock up. Thats what I'm hoping anyway.

 

[mikejpss]

Man, did I hit the jackpot or what?
My BEST friend came over yesterday evening, we pulled the valve body from the bottom of my tranny. Went thru it and found 1st gear valve stuck, removed the small piece of alumimun slag (looked like casing slag) and reinstalled it all this afternoon.
For the first time since I've owned lil red, she shifts thru all 3 gears, and she shifts smoothly.
Wanna know the best part? I have MAYBE $25 tied up into this repair.
Last week , took it to a tranny shop for an estimate- quote was for $400 minimum (repairs-IF possible they said) to $1200 for a rebuild. They said was most likely it needed a rebuild, and had never seen the car !
This is the reason I like doing my own repairs- even if it takes 2 or 3 times to get it right.
The valve body removal / reinstall wasn't as hairy as I first thought.
Mike J.

 

[GerryLP]

Man, did I hit the jackpot or what?
.... They said was most likely it needed a rebuild, and had never seen the car !
This is the reason I like doing my own repairs- even if it takes 2 or 3 times to get it right.
The valve body removal / reinstall wasn't as hairy as I first thought.
Mike J.

Mike,

I am glad it worked out for you. Those shops tend to automatically (like a tranny, I guess...:L) assume that since the car is 20+ years old, that it must need a rebuild. On their behalf, you car does have 20+ years, so count your blessings if it lasts for two years or more.

On the converter question, I am running the car with a Holley and a regular (4-pin) distributor. However, I left the computer running, and to my surprise, I do not get any "check Engine" light codes. Every now and then it flickers the light, but no problems.

I used Evariste, Nut[meg], and Stingray6874 [Mike] instructions in a long posting on how to by-pass the lock-up or install a selector switch. I followed it, and now the lock-up works great, and if I want to let the 2400 stall converter wind-up, then I flip a switch, and voila (like Evariste would say), the tires hook when the engine is between 2300 - 2400 rpm.

With this type of converter, the benefit of a lock-up option helps me greatly. A stock converter probably won't see alot of mpg, but a higher stall would. Also, on higher stall converters, the possibility of converter shakeup clicks the stakes higher (I have heard stories of tranny damage or even violent uncoupling of the converter).

 

[DDLS3]

Mine is unhooked and no longer locks up. I ran with Nut and another stock 81 from Maryland to Kentucky back in 2001 and the difference in actual gallons at each fuel stop was a gallon or less. Like Gerry said the stock convertor locked or unlocked will have very little affect on milage. You may find the wireing connector tucked up into the harness on the firewall, thats where mine resides.

 

[Chris Gerloff]

Chris

Do all the 81's with the 350 turbo tranny have the lock out torque converter?

 

[Dave L.]

Yes.

 

[lone73]

Man, did I hit the jackpot or what?
Wanna know the best part? I have MAYBE $25 tied up into this repair.
Last week , took it to a tranny shop for an estimate- quote was for $400 minimum (repairs-IF possible they said) to $1200 for a rebuild. They said was most likely it needed a rebuild, and had never seen the car !
This is the reason I like doing my own repairs- even if it takes 2 or 3 times to get it right.
The valve body removal / reinstall wasn't as hairy as I first thought.
Mike J.

I can relate...
I'm getting way too tired of paying someone else to SCREW UP my car and then have to take the time and spend even more money to fix not only the original problem but repair the parts they've busted also.
I truly believe good customer service is a thing of the past.

Happy wrenching !!
.
.
.

 

[magoo]

Mike J.

Your unhooked lockup converter will work the same as a non locking stock converter. The only difference will be a minor loss of gas milage. All converters allow a certain amount of slippage between the engine and the transmission. If they didn't, you could not come to a stop in gear. The lockup feature only comes in at cruise speeds to take out that little slippage between engine and transmission which reduces engine rpm slightly increasing gas milage. The lockup is the first to kick out when you step on the throttle or go up a hill that requires more power. If even more acceleration or power is called for the transmission will shift down to second, (passing gear). I would consider fixing it if you do a lot of highway driving. Otherwise if it's not something that will haunt you cause it's not workin you can let it go. This is something else that with a little research you can probably fix yourself at minimum expense.
I sure agree with everyone that you get a lot better value doin it yourself. What you lose in experience, you gain many times over just because you care. Just my .02. Hope it helps.

Mike J.

 

[Chris Gerloff]

Chris

Yes.

Thanks