jims427

I realize one of the weakest links in launching a mid-year from the starting line is the rear end assembly (half shafts, side yokes, U-joints, T-arms, etc. I don't want to look in my rear view mirror and see a trail of broken parts and oil strewn across the dragstrip after leaving the starting line.

Therefore, I welcome some input on how to beef up the rear assembly to handle a few blast down the quarter mile. My 66 is a 427/425 with 4:11 gears and a centerforce clutch. I also have a Lakewood scattershield to hopefully keep my legs in one piece. I will probably want to use widest Mickey Thompson's ET Street Slicks I can stuff under the fender with no cutting, but will utilize the offset T-arms.

Thanks in advance for your feedback.

MasterDave

The cheapest thing to break (loose) is the tires. Stick with DOT and step on it. You'll be fine. What I do is leave the line under 2500 rpm and slam the throttle at about 20 mph. :thumbs:

MikeM

There's a lot of wisdom in Master Dave's words. Another thing that will help save driveline parts is, when you stage, lightly engage the clutch just enough to pull the "slack" out of the driveline. This lowers the shock factor when you nail it.

Mike :)

mrg

My car had a tendency, upon a dump-the-clutch hard launch, to skew sideways left to an angle of about 30-45 degrees. I would have to steer into the slide to keep the car pointed straight. I never did this in traffic, knowing what would happen .. ! ..

The rear gear is a 4:11 posi and as far as I can tell, seems to work normally with no noise or any other indicators that would point to a problem. Would you guys have some idea as to what might be going on with the "sideways" thing .. ? ..

mrg

toddalin

Your BB should have caps to hold the u-joint where the half shafts meet the pumpkin. Small blocks have U-bolts. Be sure you still have the caps.

Install the Guldstrand aluminum bushings at the pumpkin and cross-brace to reduce the pumpkin's tendancy to move around. This movement can break parts and hurts traction. Also be sure that your u-joints are good and WELL lubed. If you are serious, you can get stronger u-joints that have no provisions for a zerk fitting. The fitting represents a weak point in the u-joint. If you are really serious, install loops on the drive shaft and half shafts. This way when a joint does go, it won't take out everything else with it (like it did once on my '64 on a launch).

As for your rear end commin' around, make sure that the car is properly aligned and tracks straight with hands off the wheel. Lots of torque can easily induce a fishtail so as a last resort, you may need to temper your right foot (God forbid).

jims427

I did a little research and I plan to add the following, but I'm open for additional input.
1. Heavy duty side yokes
2. 3 inch half axles
3. Solid U-joints
4. Heavy duty rear end cover
5. 90/10 & 50/50 shocks
6. New front springs
7. Rebuild rear end

DansYellow66

All helpful stuff you've listed above but Master Dave is right. Unless you plan to drop a whole lot of money in the rear suspension stick with a modest size tire. I haven't run my 427/425 (w/L-88 parts) on the strip since I restored it, but I repaired enough damage to the underside and driveline from previous owners to know what big tires hooking up a fairly stock Corvette IRS and 427 motor will do. :steering:

427Hotrod

The center section is really pretty strong considering its' size. My car has small lip flares and I was able to use 10x26s' slicks on it. I can tell you that even that little tire can hook up enough to bust stuff.

My std. launch with 427 was similar to everyone elses....I came out about 1500 rpm or so and once it got rolling I pounded on it hard. It ran low 11's everywhere driving like that. But....

The MPH was good enough for a high 10 sec pass, and I set it up one night to try for it. I installed the 90/10 shocks, removed swaybar and THAT combination made a huge difference in how it hooked. Weight transfer is fantastic!! I managed to launch at 3500 once and it hooked hard enough to bog, which was something it had never done in its life. I came around to line again and on the second attempt it snapped an outer stub axle.

The next time to track with 540 installed, I was attempting an easy "mph" run and was coing out just off idle. About two ft. into run a U-joint died.

The point of all this is that it doesn't take a lot of tire to hook one up.

I think you definitely need to look at some aftermarket outer stub axles, solid u-joints in 3" shafts (late model C-3 stockers if nothing else). Inner axles are next, but by the time you get that far, you're looking at upgrading posi etc. I think I'd wait 'till I had trouble and do the rest first.

The aluminum plates on crossmember will help some. Make sure you have a good rear spring and a set of Smart Struts will really help keep tires straight during launch. Stock geometry goes through lots of camber change during launch which is bad for traction AND parts.

Sounds like rear is out of alignment, specifically toe. I would bet it is toeing out on a launch. That can come from worn parts or just a need for an alignment. You have to get someone who really understands Vette stuff to align one. I do my own because I have about ZIP faith in alignment shops and alignment machines. Very few are repeatable. You want to use basically stock toe specs. It may seem weird, but DON't shoot for "0". You have to have at least 1/16-1/8" toe in minimum to keep it from toeing out under acceleration and pulling to the side. You must look at EACH side separately. Many cars are aligned and they DO get toe set, but the wheels are actually pointing to right or left. You must check the rear to the centerline of car or to the front spindles/frame to make sure they are straight.

Look at 'ole Bence...he has made many passes on slicks with his 468 four speed using a used 4.11 diff. So far he is still together and he's running low 12's. With stockparts they will eventually break something..but if you don't just kill it on every launch, you can get by a long time.


JIM

Van Steel

Hey Jim,
I make the 3 1/2" HD half shafts. They use factory size u-joints also. We use Spicer u-joints and everything is cryo-ed. I also make HD caps for the u-joints. Give me a call or check out my web site. http://www.vansteel.com

Dan