Ken Lanham

Hello,
I just joined the list, am doing some research and learning about C4 corvettes. I may be a corvette owner in the next few months. Im just trying to decide what I want, exactly.... I have a history of building some pretty hotrodded cars. I have lots of automotive knowledge, and some good mechanical skill. So I know that any corvette I end up with will probably not remain stock forever. I just have to learn the intricacies of the C4 cars, and narrow down my choices.

So does anyone have any feedback about my subject line question? I like manual transmission cars. I have rowed my 3600 lb. mustang into the low 11s (10s @ sea level easily.) Can any of the corvette manual transmissions take this kind of abuse? Say for example 500 ft-lbs torque, and 450-550 HP?

I know it sounds extreme. I just want to know the limits. I have been around GM slushboxes enough to know they can be built to take just about anything I would throw at them. But for a street/drag/road race car, I'd prefer a manual transmission. Am I asking too much? Opinions on both the Doug Nash and ZF boxes would be welcome.

Thanks in advance,
-Ken

:chevy :smash:

scorp508

Lots of em. :yesnod:

vader86

ZF6 can handle pretty much anything you throw at it. And if it doesnt, the guys at ZFDoc can build one to take over 1000hp for you.

scorp508

The Doug Nash is a Borg Warner Super T-10 with a 2-speed overdrive bolted to the rear of it. The ST-10 can take the abuse. The ZF6 also can take the abuse. The 1989-1992 ZF6s are even stronger with straighter cut gears than teh 93-96 models.

Ken Lanham

Thanks for the info. Sounds like the ZF is plenty strong for me. I'll make a mental note of that. But, I have looked at some earlier cars. Less money spent up front on a car would mean I could play with the motor a little bit right away. (I'll save the LT1 vs. L98 questions for another day)

Will the overdrive unit on the early Super T-10 hold up to a high torque motor?

Here is another barage of questions about the T-10. Answer breifly by number if you like. I don't want to wear out anyones fingers yet. I dont even know you guys yet.

1)I imagine you drive the DN like a four speed unless you are cruising on the hiway for mileage right? Road racing and such would just use the standard 4 speeds with a 1:1 4th gear?

2) If some pesky viper wants to play on the hiway while in overdrive/cruising mode. Can you just put the pedal down, and downshift from OD under power? (I know the answer to that probably).

3) Does the trans shift well? I have driven T-10s before. But only with old school external shift linkages. I am guessing the corvette version has an internal shift rail of some sort right?

4) Aftermarket shifters available?

5) Any clutch limitations, or other weaknesses?

6) Do steel bellhousings fit in corvettes? I like my feet where they are.

Nice active list by the way. Thanks for the speedy replies. :)

-KL

vader86

No, please run a search on that, we dont need another 3 page debate on which is better.

:rolleyes:

scorp508

Well, I do not want to comment on 1984-1985 as I'm not sure. The 1986-1988 units had upgraded internals. In 1987 and 1988 the Callaway Twin Turbo corvettes came with a 4+3 unit and it was fine. Those were MEGA HIGH TORQUE engines. :D They did ok! The main thing about a 4+3 is keeping its fluids and filter fresh. :yesnod:

My car right now (4+3 car) is making about 432 ft/lb, and should be a bit higher once we tune the ECM.

Correct. That is what it is like if you turn the overdrive program off via the switch. :yesnod: You do have the ability to let the computer control overdrive. It is pretty neat once you get used to it. Also has a cool kickdown feature when it sees 70% throttle.

Depends on the year of the 4+3. In 1987 (my car) if you step on the pedal and the computer sees >70% throttle it will kickdown out of overdrive automatically without hitting the switch and accelerate. It will not re-engage OD until you are in 4th gear and come under 70% throttle. You do have the option of manually turning it off too. This is what I do as the stock computer program will automatically shift into OD at 103mph if you leave the program on. This is good for the stock powercurve, but not a modified car. I can pull 4th to 150mph now, so I disengage the program. This can be modified in the ECM to a different value.

It is the same side mounted external linkages. You can tighten it up with some tricks, but otherwise it is like any other T-10. The ZF6s have the top mounted shifters.

Not directly. I have seen somebody modify a hurst shifter before to work, but no 'drop-ins' are out. You can get a short shifter kit that cuts the full throw (like 1st to 2nd) from 8" to 4".

I have a Centerforce Dual Friction clutch (cost $345 for the whole setup) right now. It should hold more power than I'll be able to throw at it. The CF feels smoother than the stock one and has less peddle effort. Like I said before the weakness is the fluids. Keep the OD flushed/filled once a year or every 12k miles and you'll be ok.

Lakewood has shatterproof ones available to fit! Also can get a kevlar blanket if you want to.

No problemo. :)

sinistervette

I was told by forum members, (I'm new here also first vette, 1985 4+3 had for 1 month! :D :cool: :cheers: ) that the calloway turbo cars used these trannies and had no problems!
1 = YES
2 = Mine has a detent cable that acts like an automatics kick down.
3 = trans/shifter can be made to shift good. still external linkage :(
4 = none that Ive found, although I'm considering trying to fit my Mr.G vertical gate into my vette this winter.
5 = only thing I'd say is the hydraulic system. I'm still getting used to it!
6 = I just helped a buddy fit one into his vette. He allready had a scttershield from his nova, we welded the origional hole for clutch fork shut, and plasma cut a new hole in the location of the hole on the stock bell housing. The biggest trick is mounting/using the slave unit. We've just about got that done. I'm not sure if lakewood has one available or not, but that is the brand of the one for the nova.
In my opinion, if you could afford too, get the early vette, and maybe swap in a ZF6. There are guys here at the forum that have done that! :cool: Whatever you decide, get your vette, enjoy, and welcome to the forum! :cheers:

Ken Lanham

SHWEEET THANKS!

Vader, I'll have some pretty specific questions about motors when the time comes to think about. I ran some searches and saw some of those immense posts you were eluding to.

There's not nearly as much good info about the gearboxes out there. I'll file this post away in my personal archive. I did notice quite a few 6 speed LT1/4 cars in various places on the internet that were in the 11s. That speaks well for the ZF trans..

scorp508

I have a REALLY good link on the story of the 4+3 at work, remind me tomorrow to post it for you. It also outlines all of the upgrades done to it I believe.

Nathan Plemons

A forum member here is running 11's with only 374 rwhp. 4.10 gears do wonders for LT1/LT4 vettes. I would be VERY close with 4.10 gears myself.

scorp508

Ken check this link out....
http://corvetteobsession.homestead.c..._dougnash.html

Beach Bum

Forum member Bowtye8 has run low 11's in his 85 stroked vette... I think he started with the 4+3, but eventually destroyed it, I think his last transmission that he apparently likes is the ZF 6 speed.... with that transmission I know that he has run 1.5 -1.6 60fts and 122+ trap speeds....

He has a webpage.... you can link to it from my webpage at:
http://www.corvetteforum.net/c4/beach_bum/

He is listed within my links section under Two stroked vettes... his brother in law also has a low 11 second manual C4.... I think he also runs the ZF, but don't remember for sure.

good luck
Beach Bum

ghall

lcvette's dad(NCChris)----ran an 11.51@122 in a lt-4 w/ stock tranny stuff-is that what you are looking for?????????????

Geoff

gcrouse

As mentioned above the ZF-6 is one strong *****. The 89-90 had the straight cut gears and are the strongest (and noisest.) First of all, you'll never get that kind of torque to the pavement without slicks; then you'll break the U-joints, clutch, halfshafts, spindles- in mostly that order- before you get any trouble from that tranny.

See my sig for what I'm putting thru it (with a McLeod dual-disc clutch). But I roadrace which ain't nearly as brutal as the 1/4mi.
:cheers:

gcrouse

While trying not offend Scorp too badly; the 4+3 completely sucks compared to a real 6 speed. :yesnod: How'd I do?

While many have done swaps, buying a vette with the tranny you want and the Dana44 rearend is so much easier. But since you like to build cars, another possibility is installing the newer Richmond (Doug Nash) 6 speed which is probably the strongest > 4spd manual you can get. Wait a sec- there's a Borg-Warner 6spd in the Viper isn't there- but I think it's big.

scorp508

:lol: For a $$$$$ tranny the ZF6 better be good. I still think the 4+3 is a great tranny when learned how to use and in its element. Kicks butt for autocrossing with that downshift and is very sneaky for street racing. :D The top end it gave was also killer for its day.

Viper has a T-56 doesn't it?

bogus

There are a few rules of thumb when dealing with C4s...

1) the newer the better.

2) Newer is not always better.

Ok... that is out of the way... I will outline my vette:

1992 LT1, with a 6spd ZF

There are pluses and minuses to both... the L98 is a great motor, and power is just as available there as it is with an LT1. Redline is redline... Sure, from the facory, the L98 does not match the LT1's redline, but gee... there 350 maxes out, practically, at about 7000rpm... so that really does not matter.

If it was my choice, considering what you want to do, get an 89 or 90 with a 6spd. see? the best of both worlds.

The chassis was massivly updated for 1988(or was that 87?? where is my black book!), so, other than tuning, there is not much difference after that point.

The 6spd is able to deal with about 650hp and 650ft-lbs of torque. That is the factory rating. However, I suspect that is a somewhat conservative number.

As for the 4+3, they are tricky to rebuild and getting it worked on is not that easy. Parts don't seem to be the issue, tho...

There are aftermarket transmissions, too... Richmond makes a 5 and 6spd. They are NOT cheap... $3000+?? ouch.

There is one last 6spd detail... the 6spd uses what is called a dual mass flywheel. This flywheel effectivly works like the springs in a friction disk. the dual mass helps to quiet the rattles inherent to the ZF. it can be replaced with a single mass, which can weigh nearly 30lbs less! A dual mass is HEAVY - 40lbs or so!!! Aluminum single mass flywheels weigh about 14lbs or so... but a single mass will cause this noise which will sound a lot like a diesel... :)

The best shifter upgrade for the ZF is the Hurst. I have one. It rocks. best bang for the buck... and it won't harm the transmission. You see, as I understand it, the B&M Ripper increases the angle of the shift rod quite bit more, putting undo stress on the shift rails. The Hurst does not do this.

Ken Lanham

Hey Bogus,
Even before getting to your post, I was starting to come to my own conclusion about the 88-89 cars with 6 speeds. Glad someone thinks like me. That sounds like a great combination...L98 and 6 speed.

Funny you mention the noise. The Tremec 5 speed in my mustang would make that rattling noise like a diesel too. I searched and searched my car for the source of that rattle before just giving up and accepting it. Someone later told me about gears rattling and making noise in some gearboxes. Especially of you have a rumpy idle. Sure enough, an ear on the gearbox case showed the noise coming from there.

Not sure how much I will have, or will want to spend on the car. But, i think an LT1 car may be just out of reach price wise. The L98 cars seem to be a touch more affordable and more in my anticipated budget.. 6 speeds & L98. Sounds like where I am headed...

Raistlin

yea scorp, vipers, c5's and camaro/firebirds have T-56's.

i got an l98 with a 6-speed and i absolutly love it. the 90 has the new style interior, with the old exterior. 90 also has *the* best looking stock wheels, except grand sports.

89 was the first year for the 6-speed, 92 was the first year for the LT1, 91 was the first year for the updated exterior styling.

the only down-side to the ZF6 is the outragious price ($600-800?) for the dual-mass flywheel and the recommendation that it not be resurfaced.
do a search for dual-mass/single-mass and clutches and you'll see what i mean.