Question: 79 Transmission/TQ Converter Help

[Vette79]

OK, so this past spring we completed a top-end rebuild of my original SBC 350 in my 79 Vette. We are in the final stages of tuning it. I now have the funds to move on to replacing the original TQ Converter with something a little more geared towards performance and quality. I have a few questions.

1. What is the stock transmission in an early 79 Vette L-48?
2. What is the stock TQ Converter in an early 79 L-48 and is it a lockup TQ Converter?
3. I am thinking of a 2400 or 2600 Vigilante TQ Converter but looking for some feedback...

Here is the link to my top-end rebuild to bring you up to speed if you have questions related to what was done:
http://www.corvetteactioncenter.com/forums/showthread.php?t=103334

As always, thanks for your input...

 

[6880 Mike]

...1. What is the stock transmission in an early 79 Vette L-48?...

TH350

...2. What is the stock TQ Converter in an early 79 L-48 and is it a lockup TQ Converter?...

If memory serves, it's a standard converter and does not lock.

 

[Rodney Gold]

Car will be a lot peppier with the higher stall , less creep too. You will notice it on the street if you use a 2400 but it will be a lot more tractable , fuel economy will go down. Add a shift kit and perhaps even a rear gear change of 15% or so and it will really wake up.
I have a 350 hp 1980 and there was a marked difference tween a 1700 stall and a 24-2600. My car explodes off the line or at stop streets and robots and the rear end is all over the place rather than squatting and getting on with it, but its still driveable tho. Its just a lot more violent when you floor it.

 

[Evolution1980]

If memory serves, it's a standard converter and does not lock.

A lock up torque converter didn't start until 1980???

2. What is the stock TQ Converter in an early 79 L-48 and is it a lockup TQ Converter?
3. I am thinking of a 2400 or 2600 Vigilante TQ Converter but looking for some feedback...

Well, if 6880 Mike is correct, then the lockup question is answered. If the first part of that question is asking about the stall speed on the stock TC,...I don't know that answer.

Now, with regards to what is best for your new engine...(If my understanding is correct)...When determining the RPM stall speed, it's better to determine where your main driving RPM range is going to be. You more or less want the stall speed to be matched to your average RPMs when driving. The stall speed is when the TC is rotating the same RPM as the engine and thus you have no slippage. That's the ideal 'stall speed'.

Racers usually have a higher stall speed transmission because that's where the engine stays more often. Daily drivers have lower stall speed for the same reason: lower average RPM range.

 

[Crimson Thunder]

What rear end gear do you have?If your cruise RPM's are less then your stall speed the trans fluid will get hot fast.You might want to get an auxilary cooler just to be safe.

 

[Evolution1980]

If your cruise RPM's are less then your stall speed the trans fluid will get hot fast.You might want to get an auxiliary cooler just to be safe.

True, but from what I've heard and practiced, he can likely first get away without the aux cooler (as long as he has a trans temp gauge), as keeping the trans fluid too cool is almost as bad as too hot. If the fluid doesn't get up to operating temps, it won't necessarily function correctly. That's one of the reasons I've heard as to why it's plumbed through our radiators. Not so much to cool the fluid as it is to get it up to operating temperature quicker.

Adding an aux cooler afterwards is a pretty easy job if it is determined one is needed.

 

[6880 Mike]

...Well, if 6880 Mike is correct, then the lockup question is answered....

Ole 6880 Mike may not be correct, but I'm thinking none of the TH350s before 1980 had lock up converters. Someone chime in.

 

[Vette79]

My research shows that the TH350 did not have a lockup tq converter until 1980. And if it did it would be a TH350C? In any case, I'm hoping to avoid installing an additional cooler if possible. The rear end is stock. I believe it is a 3.55???

 

[Evolution1980]

The rear end is stock. I believe it is a 3.55???

For automagic transmissions, yep, according to our Model Center.

 

[Crimson Thunder]

You should be fine with the 3.55's.I would be a bit nervous with 3.08's.A trans temp gauge is probably a good idea.

 

[Vette79]

You should be fine with the 3.55's.I would be a bit nervous with 3.08's.A trans temp gauge is probably a good idea.

Even if I go with a 2400 stall would the temp get that high? Also, how is driveability affected at speed say around 65 or 70mph?

 

[Rodney Gold]

I drive in South Africa , temps get real high here , with a 2500 stall and 3.55 rear gears. I do not need a trans cooler. I drive hard , race and street daily driver duty, traffic jams etc. I can also tootle along at 2000 rpm all day long with no problems. You will notice almost no effects with the TQ at low rpm , my car still creeps at 800 rpm idle. At 70 odd mph , the TQ will act like any other.
The only time I have ever really noticed the TQ is when trying to reverse up an incline??
As far as I am concerned , it was one of the best things I did for making effective use of the cars power. I have a shift kit in my TH350 , I think this also helps re box surviveability as it raises the line pressure and the clutches engage quick rather than slipping and generating heat?