Clutch/Winter Projects Advice Needed

"JayZAyEighty thinks C4+3=C7" (jayzayeighty) 11/19/2014 at 21:28 • Filed to: None

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It's time to dump all of my money into the Corvette this winter to perform a slew of preventative maintenance. First of all, there's the issue of clutch and flywheel: I really would like a lightweight aluminum flywheel. I'm looking to get into autocross and track days sooner or later, so I feel that the want is justified; it also seems like a good way to wake up a lazy old SBC. I don't need to handle too much power with the clutch, so a normal-but-reliable clutch will do just fine. I can't seem to find a clutch kit to meet those standards. Then there's the issue of the differential: to get to it, the driveshaft and exhaust must be removed. These things have to be removed anyways to drop the transmission to replace the clutch. It needs diff fluid, but would it make more sense to install a positraction rear end from a Z51? Also, the rear suspension has to be disassembled for such a job so luckily I have some new poly bushings sitting in the garage. Lastly, the car makes a noise when I turn the wheel at low speeds which means it needs a power steering fluid flush or a power steering pump. Hopefully the former. Anyways, should I just go with a regular clutch kit with a steel flywheel and should I go broke to get to the differential, and if so should I

a) just add diff fluid to current open diff, or
b) buy a posi rear end for $340?

Also, is that not one of the most 80s pictures on the internet?

Bandit > JayZAyEighty thinks C4+3=C7 11/19/2014 at 21:38

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Posi

JayZAyEighty thinks C4+3=C7 > Bandit 11/19/2014 at 21:51

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Yeah, I've definitely come to that conclusion. I'm wondering whether the automatic transmission rear end will fit the 4+3...

JGrabowMSt > JayZAyEighty thinks C4+3=C7 11/19/2014 at 21:51

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My wagon isn't as old as your 'vette, but I'm going to say if you're going to take things apart and you're looking to beat the car a little bit, it makes sense to upgrade it while it's apart. You can take the cover off the diff and decide whether it's in good enough condition to warrant just a fluid change or if you're getting chunks of metal.

Good visual inspection is more important and a better indicator than a guess and check with fluid changes.

The clutch I can't really help you with, the wagon is an auto. Eventually it'll be converted to a manual, but not right now. A properly weighted flywheel and a sport clutch would outlast the rest of the drivetrain though, and would improve drivability immensely. I would talk to a local shop if they have experience with it. My shop is using my wagon as a little bit of a guinea pig, because they know german cars really well, not so much american cars. I'm okay with that, provided we're open with each other about problems and setbacks.

For the rear diff, I would also consider a Quaife or see if there's a Wavetrac for your car. I don't know specifically. I know I'm eventually putting a Wavetrac into the wagon because it's cheaper than a similar Quaife unit. It would retain the stock look, but end up being a lot better on the track and also provide better traction in worse conditions. Also, make sure you open every door and window and turn on a few fans pointing in the opposite direction when you do the diff fluid. Get a gas mask while you're at it. If you think burned up ATF smells bad, you're in for a whole new world of hurt.

With the low speed turning noise, I would suspect seals on the steering rack. You'll want to inspect it really closely for any signs of even a little leakage. If the car will be up on jackstands or a lift for extended periods of time, it makes sense to just slowly tear away at it until you find everything that you can possibly repair. Hurts the wallet, but is still cheaper than anything else. Also, if you're dropping the exhaust, think about doing the cats. If they're older and starting to get clogged, you will see a really impressive gain by putting on either high flow cats or just new ones. Opening the existing exhaust flow will provide you with a very good increase in engine response overall. Also, if you have a bit of money, you could take the driveshaft to a shop and see if they can check it's balance. If it's going to be apart, I would consider it.

I put together a spreadsheet with a to-do list on my car, complete with links and prices so I could budget money and organize what order to do things on the car. It might help you to do something similar.

unclevanos (Ovaltine Jenkins) > JayZAyEighty thinks C4+3=C7 11/19/2014 at 22:20

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The flush won't do anything, the pump is worn out. Get the posi-trac if you're doing the driveline in the winter months.

Rock Bottom > JayZAyEighty thinks C4+3=C7 11/20/2014 at 12:22

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A light flywheel usually makes cars a pain in the ass to drive in parking lots and stop-and-go traffic, but I would think that the substantial rotating mass of your grand old small block will minimize the pain. I'd do it. Especially if this isn't your one-and-only car.

At anything near stock power levels, I would expect a stock-replacement clutch to be the hot ticket. They're usually good for hundreds of thousands of miles if treated well. Judging by your past posts, it's obvious you know your way around a machine so you should get a long, happy life out of it. Luk makes pretty good stuff, for stock clutches. If you want to get fancy and spend some money, have a look at ACT. I've used ACT clutches a few times and never had a problem with them. Once I used an ACT pressure plate with a stock-replacement Valeo friction disk on a back-yard-turbo-Saturn I built and it was perfect. Don't use a Centerforce. Ever. Even if it's free.

Oh, and you may want to check that limited slip closely if it's used. Clutch-type LSDs do wear out with miles, and if the fluid wasn't kept up (or if the wrong fluid was ever used) it may end up being a peg-leg diff anyway. If it's new, on the other hand: GET IT! It'll change your life. The first time you hang the ass out, you'll know exactly where that $340 went and what it's doing for you!

Sidenote: I'm still jealous of your 4+3...

JayZAyEighty thinks C4+3=C7 > Rock Bottom 11/20/2014 at 22:07

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Haha thank you for your appreciation of such fine art in transmission form! And I'm still jealous of your C5 for sure, although without an "the world's first computer-activated manual transmission" I just can't see it keeping up ;)

I definitely see the aluminum flywheel being an annoyance in low-speed situations, but I don't think it would be too bad on an iron head L98... it's no sure bet, though. However, it's my one and only car for the time being (but a 10 minute drive is not really concerning). The only recommended stock replacement clutch I'm seeing for sale from major suppliers is a Ram unit for $315. ACT seems like a great option but I can't find one for my car—probably because I'm on my phone. The back yard Saturn build sounds interesting. Here's a complete noob question: will the same 3.07 Dana rear diff used on both MT and AT cars be cross-compatible? Because the used one I found is for an automatic and I have yet to find another that came with a manual. Both are 66 model Dana rear ends. Thanks for all of that info!

JayZAyEighty thinks C4+3=C7 > JGrabowMSt 11/20/2014 at 22:14

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Wow, this is super informative. Thanks! I should probably disclose that I can't afford a new diff; I'd be buying an original Dana 66 Positraction 3.07 rear from a Z51. The work is primarily being done by a couple of mechanics I know because I don't have the expertise or tools to do it by myself. I was thinking of doing a resonator delete, but I'm afraid new cats aren't in the budget right now. Matt Farah cut his out, and my car is exempt from emissions. I'm going to follow your advice on that spreadsheet, though, and I really love the idea of a manual transmission in the wagon!

JayZAyEighty thinks C4+3=C7 > unclevanos (Ovaltine Jenkins) 11/20/2014 at 22:16

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Ah, that's what I've been hearing. I'm going to be disassembling the rear end to get to bushings and the differential anyways, so replacement just makes sense. Better performance and more fun.

Rock Bottom > JayZAyEighty thinks C4+3=C7 11/20/2014 at 23:16

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To be honest, I know very little about C4 diffs. They might be the same, but I really have no idea. Dana 66 you say? That just sounds unfamiliar... And have you considered a steeper ratio? Maybe a 3.42 or 3.73ish number? What's your 4+od ratio? God that felt weird to type...

And for your clutch, you might try giving a stealership parts department a ring. If they want anything close to that $300, then I'd get the Ram, but they may surprise you. Those Rams are really good clutches. It's likely ACT doesn't build clutches for our cars... I never thought to check.

As for the Saturn, you really had to see it to believe it! Methanol injection, cast iron water pipe exhaust manifold, Thunderbird turbo, and like 200 zip ties! I loved that little plastic car. I traded more beer for parts than I ever thought right...

JGrabowMSt > JayZAyEighty thinks C4+3=C7 11/20/2014 at 23:42

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Look up price for high flow cats, and at least have it in the back of your mind. Personally, I think it's important to be as environmentally mindful as possible. Sure, many cars can get a cat delete, but it's something that just doesn't really appeal to me. I respect both the environment, and my want to continue hooning in it. I also need to pass inspection.

Resonator deletes are not bad ideas, it can really change the sound of a car. I'll be doing a resonator delete and high flow cats with low restriction mufflers in an effort to breath better, but I'm not doing it at the expense of drone on the highway or too much noise in general. If I leave my house at 5am for a car show, my neighbors don't need to know.

A 3.07 rear doesn't sound bad actually, is that the same gearing as it currently has? No matter what though, if the budget pours into something, embrace it. That whole "you get what you pay for," will always come back. The clutch and flywheel are things that should be expensive and high quality. Even if something happens to the car, take them out and sell them separately. Given that your list is really just: 1) clutch/flywheel 2) rear 3) power steering noise and 4) exhaust mod 5) bushings, you should be pretty set. The clutch/flywheel will probably be the most costly parts, while the power steering will be the source of most labor charges. Dropping the exhaust and popping the cover off the rear will be a very quick indicator of what your best action is. I'm a very big fan of minimally invasive diagnosis, so there's that.

Much like your list, I have a bit of suspension related work that I need to get through on the wagon at some point, looking like it'll wait until the spring as well.

You must get some pretty good highway MPG out of it, if the 3.07 is lower than the current rear, that should go up as well even more too...

JayZAyEighty thinks C4+3=C7 > JGrabowMSt 11/21/2014 at 16:53

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Yeah, I don't want to go out of my way to harm the environment either, but I'm not sure whether the cats on my car even do anything. I'll probably just wait until I can do the whole exhaust, although if I can I'll do a resonator delete. I'm looking at a Fidanza aluminum flywheel and Ram clutch, and both companies seem to have a good reputation. The current ratio is 2.59 for the stock open diff, so 3.07 will make things better from the driver's seat without being too much of a drivability detriment; I'll probably see my gas mileage go down a little on the highway but the 4 OD gear is really tall and I mostly do torturous city driving anyways...

JayZAyEighty thinks C4+3=C7 > Rock Bottom 11/21/2014 at 17:14

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Sorry about that, I meant to write Dana 36. It's for pretty mild driving so I'm fine with the Z51's positraction diff; that's all I can afford in addition to the clutch/flywheel at this point. I'll be sure to look into a dealership parts counter, though. If it's much cheaper that'd be a worthwhile route. The Saturn sounds insane, though!

JGrabowMSt > JayZAyEighty thinks C4+3=C7 11/21/2014 at 17:31

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Fidanza I've heard of, but have no direct experience with their products. Ram I don't know. A brand I've always liked is Sachs, their stuff is often OEM in many cars, but the quality is crazy good.

2.59 to 3.07 isn't so bad. I'd only be really concerned if it were over 3.07.

JayZAyEighty thinks C4+3=C7 > JGrabowMSt 11/21/2014 at 23:33

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I was totally wrong about the diff stuff. I already have the 3.07 Dana 44! It's the '84 manuals and subsequent automatics that have the 36 and even that's positraction. Ram seems to be big in the older American car scene, but I'll be sure to look at Sachs. Thanks for the advice.

Rock Bottom > JayZAyEighty thinks C4+3=C7 11/24/2014 at 08:49

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Ahh, the D36! I've heard of that one! Are they sturdy? And if you're buying the Z51 posi used, I would still make good and sure it isn't worn out. You don't want to end up in the same place you are now, but a few hundred bucks lighter!

And that Saturn was... interesting. It was cobbled together and I was never happy with how the methanol injection worked. I drove it for about 2 years and never stopped tinkering with it. That car was the definition of "Inconsistent Performance". Some days it was a 14.00 car, others it was a 16.50 car. One thing that was fun was to mix a gallon of toluene and a little ATF with a tank of high-octane and let it spit flames out of the tailpipe. Seriously. I had a nice scorch mark on the back bumper!

JayZAyEighty thinks C4+3=C7 > Rock Bottom 11/25/2014 at 20:10

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I was actually wrong about all of this. All post-'84 manual C4s (Z51 or not) have the D44, which is quite sturdy and well-known. So I'm just going to pump in some synchromax and Posi additive and keep going with the stock 3.07. And that Saturn sounds like a riot; 14 seconds is nothing to scoff at in a FWD car!

Rock Bottom > JayZAyEighty thinks C4+3=C7 11/26/2014 at 08:24

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Oh yeah, the 44 is a monster! Damn truck parts!

JayZAyEighty thinks C4+3=C7 > Rock Bottom 11/26/2014 at 14:34

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Yeah I can't believe I forgot about that! The D36 couldn't stand up to 330 lb/ft without a slushbox in between, so they switched to a 3.07 44 luckily.