My opinion is gears and then exhaust.

 

My $.02, as long as you don't have any exhaust issues such as clogged cats, I think the 3.07 gears would be a nice compliment to the car. There is a reason GM named the 3.07 the Performance Ratio. And if you can have that installed for $850, that is a fair deal.

 

Hey gang-

I have 3.07 gears and Flowmasters on my "85. 19.5 mpg ramming around locally, and 22 to 23 mpg on the highway. Not bad for an "old" car with lots of miles. BTW, I have never been stopped for noise, just be sensible (when you can!).

 

I'm not starting a debate just noting that 3.73s for a street driven car is a pretty steep jump. Too each their own though. If you keep an eye on craigslist or the forum you can nab a diff with those gears pretty easily. I picked up a spare for a friend on craigslist for 600 or so a couple of months ago with 3.45s, just have to wait it out. I've also seen lots of good used gear sets go up for sale to rebuild your diff. I have my 3.07s from my D44 still and I'm sure others have their 3.33s and 3.54s which could be an option too.

I had 3.07s and now have 3.73s. (Autocross and not stock, not TPI intake, it really wraps up a lot faster, I liked the pull with 3.07s for the old TPI and SR combinations.).

LT1 exhaust is a dual exhaust system which is 2.75" (thanks 96lt4) you can pick up three hangers (2 for the differential, and 1 for the back of the trans). These I believe utilized a dual cat setup (where your pre-cats are) and then they have a resonator where your third cat is, but remaining still in the duals format.

It is a good upgrade but unfortunately if for smog they are checking all 3 cats, you are going to be in trouble. No reason you couldn't run two high flow cats with the LT1 system and be as clean if not cleaner for the sniffer, but you will fail visual. Same goes for your current system. If you were flexible...I would run a pair of random tech high flow cats in the pre-cat position and then a hollowed out center cat with a catback. Pass visual and still clean. Or for less $ you could do the same but run a single main cat and gutted pre-cats, I'd imagine dual cats would give better flow but probably cost more. Both should be as clean if not cleaner than stock, especially if using old cats.

With your difficulty of modding exhaust, I'd start leaning more towards gears or gears and catback.

 

The 88 is air flow restricted, headers, true duals with cats will wake the engine up, remove the frisbee and open up the air cleaner lid. Best bang for the buck.

Gears may make it feel faster, but the exhuast and other will add real HP.

 

FWIW the LT1 factory exhaust is 2.75".The only restriction(IMO) in the system is the resonator.

 

Thanks to everyone who chimed in and who voted in the poll (way more votes than posts, so people were voting but not commenting (which is fine)).

Good arguments made on both sides with the polling numbers favoring exhaust over gears 3 to 2.

In the end then I think what I gained most from this was that it has convinced me that I should really do both. So I guess that is indeed what I will do, in time. I will probably do the gears first since that low-mile 3.07 pumpkin is available (I know, I know, some of you 3.54/3.73 guys are shaking your heads right now! LOL! But I am still convinced that would be too much for my intended use) then start saving/planning again for the exhaust.

Doing both would certainly solve the problem of which to do!

Thanks again for the help gents!

 

Just thought I'd post a follow up/update in case anyone cares.

I did get the 3.07s and after having them a week (and driving the car quite a bit with them) I can say that I am very happy with the results.

I had read on here some saying that a change to 3.07s from 2.59s was like "night and day". I wouldn't go that far, but it was significant. Overall it was about a 20% increase in gearing (18.something actually)... and I would say that the car legitimately feels about 20% better (whether it is actually quicker/faster I have no idea as I never did 1/4 mile it with the 2.59s to set a baseline). But it definitely feels more responsive and like like it's doing the work effortlessly (with the 2.59s it always seemed like it was laboring just a bit).

The revs are obviously up a little at cruise... but now the "sweet spot" when cruising on the freeway is actually at a more usable speed. With the 2.59s this car wanted to go 80-90mph all the time... that's just where it "felt good". Now that has been backed down to 70-80mph (because the revs are up a bit) and it's actually more fun to drive at speeds that won't get me arrested! (ie, doing 85mph was great... but risky.... 75mph is a much more police-friendly speed on the freeways around here... especially when driving an arrest-me-red Corvette!).

Plus, it obviously accelerates much nicer in gears 1-3. Because in the past I have owned a lot of 2nd gen Trans Ams (many with the TH350 auto) I did a comparo against the gearing of the TH350 and the 700R4 and calculated the following from a torque multiplication perspective. My car now with 3.07s launches in 1st gear like the equivalent of an old 3.73/TH350 combo, accelerates in 2nd gear like a 3.23/TH350 combo, hits 3rd gear at 3.07:1 (obviously) and cruises on the highway in OD like a 2.13 geared car. Add to that the copious low-end torque of the L98 and it's a pretty dang nice combo.

Also, after having the swap done, I can say with 100% certainty that I wouldn't have wanted anything in the 3.45-3.73 range (see my initial post for how I use my car). While I know it would have made initial acceleration more rewarding, while cruising it would have affected where that "sweet spot" on the highway is considerably (not to mention MPGs). The 3.07s really are the perfect gear for a stock-ish L98... I can see why the factory used them.

So in the end I am happy with the results. It wasn't a cheap mod mind you... but I'm glad I did it. Sure wish it would've been ordered with it originally though... back in 88 it was a $22 option!!!! Was considerably more to upgrade it in 2012!!!

BUT NOW... as luck would have it, a week after I pull the trigger on the gears... I have been offered a set of ceramic coated Hooker Super Comp headers from a fellow Corvette enthusiast who bought them for his 87 vert but never got around to installing them and then lost interest in the car. He's had the headers just sitting around for quite a while. He's offered them to me for $390!!! I don't know how I can say no, but I'm pretty cash poor right now! ARRGGHHH!!! What to do? What to do?? Y'all will think I am if I pass on them won't you?!

 

It sounds like you did the right thing, for you. Did you correct the speedo for the gear change ?

 

Yes. Green 42T.

 

If you have an rpm question in your mind,go to richmondgear.com they have a rpm calculator just poke in your tire size and wanted gear ratio and it will give you the rpm at desired speed. or you can put inyour desired cruise rpm at what mph and it will give you the required gear ratio. if your considering gears,check it out and do it. you'll end up doing the exhaust someday anyway. LOL

 

Thanks mtnmanut, but I already did the gears (see post #28 above).

 

:***** opps; to much coffee ; i'll keep my mouth shut