Learn me C4 Corvette?

When we were doing cash for clunkers a guy brought in an '85 with a 4+3 trans. It had over 150,000 miles on it and still ran and shifted great up to the point when it drank the sodium silicate cocktail. He replaced it with an automatic Corolla.

I hope someone bought it out of a junkyard for $500.

both autos mine was 14.4 hers was 14.7

I wanted to res this from the dead.

I'm also thinking about jumping on the C4 bandwagon for an autocross car. So far my reasearch says an early L98 car with an automatic is the best for dodging cones, yay/nay? If you do go with one of these, what are the recommended mods? Stock gearing with an auto looks to be crazy high (2.60-something), do people swap in lower gears, or is the converted torque of the L98 enough that those work?

I used to have an early L98 / Z51; of all the cars I've sold, it's the one I miss the most. It's got plenty of torque and the only times I autocrossed it were on street tires; if I had geared it down any more, it would probably just spin the tires more. Needed stickier tires, and a better driver. I felt it could go a lot faster if I knew what I was doing.

An L98/auto can be great, but with two caveats: 1) The non-Z51 steering rack is a little slow, and 2) if it does not have the performance rear axle, gearing is very tall (something in the neighborhood of 2.49). Autos got a Dana 36 rear, manuals a Dana 44. If you find a non-51 car you like, there is good news: you can exchange the D36 rear gear set for a lower ratio without relaibility problems UNLESS you plan to run sticky tires or build a big motor. On stickies, neither rear will last forever with repeated hard launches. You shouldn't have any trouble with street tires, though. This option is far cheaper than finding a D44 rear from a manual trans car and swapping it in, which is a favored swap among guys who are building a track car. A fast steering rack can be changed in; it requires a lot of patience due to access issues but can be done, if slowly. If you're open to a stick, any L98 Z51 car is ideal as it will have fast steering and D44 rear. In '91 Z51 was dropped for Z07: same idea but with selective ride control. As with Z51, these are worth looking for and come in L98 ('91) and LT1 flavors (92-95). Other swaps: sway bars are easy to change out and available from many sources at competitive prices. Z51 and Z07 cars got bigger bars than base cars and you may want to do a swap after spending some time setting a baseline. Spring swaps are possible. Z51 and Z07 cars always got stiffer springs than base cars of the same year, but rates varied over the years. Hib Halvorson charted the year-to-year changes. This is one mod to definitely save for after you've spent some seat time and there are many variables to consider, especially shocks. It is possible to get a setup so stiff the tires skitter easily over surface irregularities and many owners come to prefer a somewhat softer spetup to aid in weight transfer. The RPO sticker will be either under the center console lid or under the lid of the rear storage compartment, depending on year. When shopping, check the RPOs so you will know what you are dealing with and negotiate accordingly. These cars are getting older and I'd change a rear gearset on a well-kept car rather than buy a Z51 or Z07 in marginal condition, unless it was truly cheap. There are a few other vagaries - the 1996 LT4/Z51 gave the most motor with the softest suspension, and there was a change in 1988 to a zero-scrub-radius front suspension. Feel free to PM me if you have any MY-specific questions or anyhting else.

Thanks for the info, Cones, what's your threshold for sticky tires? Current plan would be staying in a street tire class and running Star Specs.

Also, am I understanding correctly that you recommend at least the gearing from the manual trans cars (~3.08s, IIRC)?

I edited my post to clarify on the rear end matter. Neither the D36 or D44 will last indefinitely on stickies wtih hard launches. If you don't drop the clutch, you shouln't ever have a problem. Sidestep the clutch repeatedly with the revs up and you will eventually break a case. The D44 will just last a little longer than the D36. With a stock motor and automatic, the D36 will last fine no matter the grear ratio. Mod motors making significantly more hp/tq on the other hand should make you look into a D44. To answer your question, my reference for stickies is anything <100 treadwear rating, like Victoracers or 710s, A6 Hoosiers, etc. I think you would be ok on stickies with a D36 as long as you are a little soft on the launch. As far as the grear ratio goes, anything numerically higher than 3 will give you a nice result. The performance rear axle ratio for automatics was, I think, ~3.06 as you state and there are 3.30's readily available too. For and L98 automatic I'd try to keep it in that range to keep the motor from funning out of breath so fast and needing extra gear changes on longer or faster courses.

I had an '88 for a long time and it autocrossed great. I was a 4+3 car with the Z52 suspension. (A little softer than Z51, but a step up from base. Standard brakes but had the faster rack) 4+3 had 3.07 gears. I ran 2nd most of the time, plenty of torque to do the job. The O/D unit is tough, IF IT IS MAINTAINED. Mine was bad when I bought it, but never had an issue after a rebuild. The trick is to not let it shift on it's own. Push in the clutch and shift it manually. A bad O/D unit won't disable the car, you just won't have overdrive.

^ That. I actually enjoy the 4+3. It's tough, simple and works well.

Z52 is worth having. For autox, base brakes with good pads are more than enough.

Would any C4 owners consider taking a one day 600 mile trip in their Vette? Or have taken...

I wanted to take the '91 Miata out to the GF's parents house 600 miles away, but we both agreed it would beat us up a little too much. That and cargo space is a little limited on the miata...

I would only be interested in DDed or fair weather type C4s since that is the role of my Miata.

RossD wrote: Would any C4 owners consider taking a one day 600 mile trip in their Vette? Or have taken... I would only be interested in DDed or fair weather type C4s since that is the role of my Miata.

I used to take my '89 to boston, about 550 miles away; all highway.

With cruise and the 6 speed I would make the trip on one tank of gas (best run around 29 mpg)

Not too bad for a highway cruiser. Tires determine if it can handle the rain; wipers lift off the windshield over 85.

I have a 91 miata and I dread driving it more than 45 min on the highway, just to show that I'm not some type of tough guy who can make a road trip in a c4.

C4 is an excellent highway car - especially with the 6 speed. Springs, damper, tire combination might make expansion strips more painful than you'd like depending on the setup, but I found wind and engine noise very low, and the TALL 6th gear resulted in relaxed and fuel efficient cruising. The seats were comfy too, but YMMV.

mine was a convertible and was driven on several multi-day road trips. about 25mpg hwy

my boss and i took her 88 to houston and back 2 days later from tulsa. not a bad ride at all. not as comfortable as my car but i think most of that had to do with the fact she insisted on having the top down and i hate convertables. hers is an auto and actually got 29mpg on our trip

My main complaint with the C4 is the limited foot space. It's also the main reason I'm contemplating selling it. Just after I get the drivetrain and suspension completely rebuilt then I go and want to sell the damn thing. I think I might need help.

They're great on the road. Be aware the L98 can have an exhaust drone between 1600-1900 rpm, right where it cruises on the highway. Many of them now have aftermarket exhausts, so YMMV.

I'll just leave these here......(found last night)

http://daytona.craigslist.org/cto/3265666412.html

Challenge Corvette? http://daytona.craigslist.org/cto/3267405483.html

RossD wrote: Would any C4 owners consider taking a one day 600 mile trip in their Vette? Or have taken... I wanted to take the '91 Miata out to the GF's parents house 600 miles away, but we both agreed it would beat us up a little too much. That and cargo space is a little limited on the miata... I would only be interested in DDed or fair weather type C4s since that is the role of my Miata.

I don't think we have hit 600 miles/day in the C4 but we've long (like 6-8 hour) drives in hours (Convertible Auto with the Z52 suspension). Cargo space in that one is Miiata-style limited (Coupes are much better) but on normal tires I wouldn't hesitate taking it on another long drive. It currently sports R888s as those were the only tires I could get in the correct size at the time and they're a little noisy.

The seats are pretty comfy, they're good on fuel for the size and fun to drive.

My biggest issue with the C4 is the wheel bearings when actually driving them. They are small bearings, and combined with large brakes and massive tires they don't last more than about a year when auto-x'd/track days.

Joe Gearin wrote: I'll just leave these here......(found last night) http://daytona.craigslist.org/cto/3265666412.html Challenge Corvette? http://daytona.craigslist.org/cto/3267405483.html

ahahah love the beach picture. Next time someone posts a 4 runner or something else on the beach I'm posting that up.

Bobzilla wrote: My biggest issue with the C4 is the wheel bearings when actually driving them. They are small bearings, and combined with large brakes and massive tires they don't last more than about a year when auto-x'd/track days.

I think they're ok if you find NOS (SKF?) bearings - the originals seem to be much longer lasting that the aftermarket bearings that are much easier to find.

Getting a little OT here, but for the front hubs there is the Firebird substitution that will save a ton of $$. Nearly bolt-in mod for a part that is about half the price of the "correct" bearing. How-to is stickied in the C4 section of the Corvetteforum.

conesare2seconds wrote: Getting a little OT here, but for the front hubs there is the Firebird substitution that will save a ton of $$. Nearly bolt-in mod for a part that is about half the price of the "correct" bearing. How-to is stickied in the C4 section of the Corvetteforum.

But even then, you're still replacing them every year. I can get Timken C4 bearings for ~$125 a corner, but that's still crazy.

That, combined with the wife's loathing hatred for being in the car are what are leading me to sell mine just as I get it running right.