How Much hp can the stock drive train take

[tscott9330]

I have a 78 vette. I plan to be making 350 to 450 hp and i want to know how much hp the stock drive train can take. If it wont stand up to the beating then maybe you could tell what all you have replaced so far aand why it broke.

Your help is appreciated

Tom Scott

 

[sscam69]

I would first upgrade the U-joints to 1350 series u-joints. The next thing I would look at would be the differential, then tranny, then clutch.

Not necessarily in that order but things to consider.

As long as you foot is not that heavy and it won't see regular drag duty. You should be alright. Just get a good clutch.

Frank

 

[JohnZ]

The driveline is plenty stout as it is, and the tires are the "safety valve" for the driveline. Things start breaking when you bolt slicks on, when the "safety valve" becomes the driveline itself, and these are the first parts to grenade:

 

[sscam69]

OUCH!!

What happened with those halfshafts John?

Frank

 

[Stallion]

I've heard the terminology of "drive train" lately and I'm afraid that I'm not familiar with what this is exactly. Can somebody explain what the drivetrain is used for and its placement in a Vette? Thanks!

TR

 

[69autoXr]

Stallion,
Drivetrain refers to everything behind the motor that transmits the power to the ground. This includes the the clutch, trans, differential, drive- and half-shafts, U-joints and even tires.

The big-block cars had a different setup for the U-joints, specifically there were bolts and caps used instead of U-bolts, and heavier half-shafts (I think). Upgrading to big block spec drive train features should allow up to any Hp and torque level any small block would produce.

I currently run a 70 spec LT-1 in my car with small block half shafts and U-joints and -bolts, and expect that one day I'll bust them up, particularly since I only use the car only for autocross with sticky tires.

 

[WayneLBurnham]

400 hp (and related torque) should be handleable by any in good condition

You ran into the weak part in the system and most expensive to upgrade of C3 parts.

The IRS is excellent in control - handling - and even in planting the tires for take-off compared to regular live axle set-ups - up to about 500-600 hp.

Past there and you start doing what I did to my left rear (not the torque wheel even) and break first outer U-joint, then inner U-Joint then half-shafts then outer axles....you get the idea.

(In my case my rear driver wheel broke off when the axle cut in half from a seized inner bearing I never even heard....)

The normal IRS third member is either a Dana 36 or Dana 44 equivalent - you can get weaker, but not easily. Feel happy- that the Dana 44 is stronger than the late C3 or C4 aluminum thing or even the C5 transaxle, but any four-wheeler would tell ya' it's the first thing they'd take off and upgrade (especially on the front of a Chevy.)

I wanted as strong as possible so i went with something of absurd cost - a custom 12 bolt IRS made by Tom's Differential. But this is not necessary unless you are building up an insane small block or healthy big block with huge meats.

You're kinda lucky in that the main driveshaft and it's two UJoints do not fail often. After all, the driveshaft doesn't move hardly at all - just slightly when the vehicle is suddenly accelerated and the the nose of the differential moves.

There are 2 general axle kit upgrades - the 1350 and the 1480. These replace the half-shaft, the U-Joints, the Outter and Inner Axles. They are mostly bolt in replacements, except the 1480 which require alteration of the differential case for the inner axle.

As the other poster mentioned, all sources say just going to the 1350 setup really buys you an enormous amount of safety. The 1350 parts, which largely refers to the thickness of the material of the half-shafts (0.135") from what I can gather, as well as bettter bolt up systems on the UJoints and thicker webbed flanging on all involved parts, are just much better than what was available from the factory originally.

No matter what you use though, nothing substitutes for frequent inspection and being critical when hearing a strange driveline noise. You really don't want your rear wheel passing you on the highway at 80.

 

[Stallion]

Thanks, 69autoXr! I didn't know that that's what was referred to when you speak of the drive train. Now I do! But just a couple of questions. I'm pretty familiar with most of those parts you listed off except the "U-bolts" and "halfshafts". Could you explain these two parts and location and function?

Thanks!

TR

 

[sscam69]

goto www.c3sharktank.com

Its Scott81's website.

Just surf it your gonna find a lot of useful information along with photos of the differential, half shafts and U-bolts when he rebuilt and upgraded his drivetrain.

Cool site BTW

Frank

 

[Stallion]

I'm looking at those pics from his site (that is a nice site! ) and I have a couple of questions. I'm looking at the half-shaft now (I think) and I'm not sure if I'm looking at the right thing.

What exactly is the half-shaft in this picture? And what is the purpose of the half-shaft? How does it compare to the drive-shaft?

Thanks!

TR

 

[sscam69]

Yup your looking right at it.

Its the shafts you see connected to the tires (for lack of better technical terms). Not sure about the "Half-shaft" name but I think its because its pretty close to half the length of the driveshaft.

The driveshaft transfers the torque from the transmission to the differential.

The halfshafts transfer torque from the differential to the wheels (what you see in the pic).

 

[JohnZ]

OUCH!!

What happened with those halfshafts John?

Frank

540 Merlin with slicks - and those are the shot-peened BB half-shafts; that's why NHRA rules won't allow independent rear suspension on cars that run 10.0 or quicker, especially on Corvettes, where the half-shaft is a suspension member.

 

[Stallion]

sscam69, is it what is going down at an angle but then connected to a partner piece, which isn't directly on the rotor? I still don't think I'm sure.

TR

 

[WayneLBurnham]

John - you have a MERLIN 540!!!

"I LOVE you Man!!!!"

THAT'S what I'm looking at for my beasty!!!!

Is yours iron or aluminum, standard deck, tall or super? Do you like it? Any problems vs. GM blocks so far? I'm looking at the new super decked aluminum one for my engine project, if I ever get to it... :cry

John - the NHRA reg on the IRS - does that include the additional "Upper Control Arm" modification made by a few vendors for that purpose? I know Tom's makes one they advertise as being NHRA approved for 10.99 and faster, but I don't know about 10.0.

I was considering that for the shopping list, but they told me at Tom's they serve no purpose in normal duty, and may actually negatively affect articulation, but are entirely to serve in place of the half-shaft when it twists in half like a pretzel and prevent the rear wheel from folding up.

Stallion - you are probably referring to the strut or camber rod.
These are the item that keeps the bottom of the wheel at the appropriate angle to the road surface.

Several manufacturers make improved versions of these - firmer bushing ends, easily adjustable and thicker and such. I noticed a big improvement in rear end stability when I had the VBP "Smart Struts" assembly put on.

What the strut rod connects to (and the lucky part that held up my puppy off the ground when I lost the rear wheel, along with the bottom part of the strut) is only called a support or extension in the Eckler's and Corvette Central catalogs I had handy - but it's an important cast iron part - hopefully it's really cast steel or nodular iron or something stronger.

 

[Ken]

I'm following this thread too because I'm going to have a need for the half shaft loops as well on my C4. The driveshaft loop itself isn't a problem, but I can't figure out how to mount half shaft loops. Got any ideas? (I already had a thread going on this subject asking for help, but seeing as the mountain won't come to me...) :L

_ken

 

[Stallion]

Okay, so if that's the camber rod, then the half-shaft is that "tube-looking" item that goes directly to the rotor? But I thought that was the shocks? Am I wrong?

Thanks!

TR

 

[fc3]

Ken, Have you seen this? Fred. http://www.dragvette.com/links2509.html

 

[WayneLBurnham]

Half Shaft is the large diameter thingy

with two similar connections (U-Joints) running horizontally that go to the center of the wheel.

The strut is the small diameter deal that run parallel to and below half shafts and attaches to that extended piece at the bottom of the wheel.

Don't confuse this "Strut" with a McPhearson strut - which is a combined shock and coil spring unit used on many suspension systems. This strut or camber rod is a solid, hopefully-unflexing piece that fulfills another funciton entirely.

The shocks on a vette run perpendicular to the half-shafts and struts. They run vertically at the end of the leaf spring. Like the spring, it has been removed from the rear end in the picture. On my '75 and other earlier C3's the shock mounts to a thing that ties into that extension at the bottom of the wheel that the strut or camber rod goes to. The post '80 lightened rear of the late C3's could be a little different, I'm not sure.

Incidentally, the outter edge of the spring mounts to that opening thing at the rear - in the picture in line with the outter end of the half-shaft, but behind it (really it's a little below the center line of that thing when assembled.) It bolts to the back edge of the trailing arm which is the big, irregular shaped thing running from the front to the back of the car, and is what the wheel is mounted on, through the addition of flange.

To help in all of these, get the vette parts supplier's catalogs.
Corvette Central (800)345-4122 had a good little picture of this on p. 139. Eckler's (800)327-4868, MidAmerica (800)500-VETT, Paddock, possibly Year One, Corvette America (don't have that one yet) and others I'm forgetting or haven't nuked credit cards on yet are valuable information resource tools, as well as several of the main manuals like the Shop Manual, the Assembly Manual and an aftermarket manual like Chilton's. There are also videos of many of these sections, including a suspension video I bought from one. Of course, many of these are on-line.

I must have spent $500 of my current $31K in on the heap in reference materials alone - and have more to go. For either a despoiling slob modifier or a perfectionist restorer, that kind of information is the most valuable planning tool possible.

You also want ot load up on generalist catalogs like PAW (Performance Automotive Wharehouse), Summit, Jegs, and JC Whitney.

 

[Stallion]

Okay, I think (hope) I know what you're referring to. Thanks!

TR

 

[JohnZ]

Re: John - you have a MERLIN 540!!!

"I LOVE you Man!!!!"

THAT'S what I'm looking at for my beasty!!!!


John - the NHRA reg on the IRS - does that include the additional "Upper Control Arm" modification made by a few vendors for that purpose? I know Tom's makes one they advertise as being NHRA approved for 10.99 and faster, but I don't know about 10.0.

Not my car - I just did the repair job to put it back together. I'm not familiar with the "upper control arm" mod for Corvettes, but Vipers have upper and lower control arms (their sliding-spline half-shafts aren't suspension members), and NHRA won't let them run under 10.0 either; several of my "wild and crazy" Viper customers that run regularly in the 8's and 9's have had to install 9" Ford axles to pass NHRA Tech and run legally at NHRA strips.