Another 3.36 or 3.54 thread...
 

Sorry I know this gets beat to death but... I am on the fence and looking for general input. I will be swapping out my 2.87 rear to a 3.31 or 3.54 soon and I am looking for some input to sway my decision. Off the line, the 3.54 would be better but on the highway (at 70 mph) it would be turning 3084 rpms versus 2883 for the 3.31 gears. I don't do a ton of highway driving but I don't want it to be a pain and sound like it's screaming.

My tranny is a Super T10 with 2.88 first (very low) so I will have overall ratio of 10.2 with the 3.54 gears, and 9.5 with the 3.31's. I've never swapped gears before so I don't know how much different these will feel. I am leaning towards the 3.31 just because of the highway rpm's unless someone can convince me that's not a big deal. Price is the same for both, so that's not a consideration. This is a job that I only want to do once, so I will live with it. And I just did the tranny, so that's not changing.

Engine is a warmed over crate 350 with vortec heads and XE268 comp cam.
Thanks :thumbs:

With a difference of only 200 rpm at 70 mph and only driven occasionally at that speed, I would go with the 3.55.

You going to be doing much highway/interstate driving? Do you mind a 3,200rpm drone?

I don't do much highway at all, but when I do it's for an hour or so. And no, I don't mind the drone. I like it :D

Well if you LIKE the drone, I'll vote for 3.55s!

I have 3.36s and I don't like the drone. I put 275/60/15 tires on for additional height to bring my freeway RPMs down. Other factors that contributed to my dislike of 3,000-3,300 rpm for long periods of time:

• My valve covers leaked oil. Sustained higher RPM resulted in more oil leaking.
• My valves seals leaked oil into the combustion chamber, which was worsened by the high vacuum condition of decelerating down a hill at 3,200rpm.
• I never quite got all the air in my coolant bled out of my system, so my radiator hoses tended to collapse at 3,000rpm +. I noticed my temperature would climb when cruising at 75mph for a while. Pushing in the clutch and allowing it to idle for 5-10 seconds brought the temp back down.

All of these things are avoided with a properly running/maintained engine with functioning seals and cooling system. Right now I have the engine out and going through a top end overhaul, so I hope to address all of these issues.... plus I'm going with a T56.

Jim, make absolutely sure you won't have a problem seeing the tach at 3200 going down the highway. This is the decision that matters the most. Everything else makes the 3.54 gear the better choice. Engine wear, gas mileage, etc do not have any bearing on this decision. Upgrade to OD, larger wheels and tires, and performance will all benefit going to 3.54.
Mike

Rookie suggestion: Going from 2.87 to 3.36 will feel as though you installed a 500 H.P. engine in your car/going to 3.55 gears will feel like a 550 HP engine.

Approx. 3.18 gears would be great highway/+MPG gears.

:iagree:

I have the 3.55 gears, and would never go with a higher gear. Heck, I would go lower than 3.55 if I was doing a swap, prob 3.73.

I dont like running at such high highway RPMs either, but I am going to address that with a 700r4. And this is a fun car, not a road trip car too.

With a mild 350 I would put in 3.70 gears and don't look back. I ran 3.70s with my original 355 for years and got 17 mpgs. With a mild cam its really not bad on the highway, assuming you keep close to the posted speed limits. Back roads,....wouldn't worry about it at all.

FWIW
I commuted 400 miles a week for six years running the 3.70 gears, tallying 124,000 miles. Then I put in the 406 and 3000 stall, and only drive when the mood hits and weather permits. Don't care about mpgs now.

Those cars ran those speeds when they were new. We've just gotten used to having overdrive transmissions.
When I first took mine out on the highway I said I'll just drive 60, the speed limit was 70 and everyone in Florida drives 80.about ten min of people driving by looking at this Corvette poking along was all I could take.I got in the left lane and was going 90 very quickly. And truthfully my car feels like it in its sweet spot at 90:cheers:

:iagree:

You'll realize how unimportant 200 RPM is every time you leave a stop light. :lol:

I have 3.55's and I hear ya. Cruising at 80 mph (not very often) but it felt like the car just wanted me to give it more and I was barely touching the throttle, so it seemed.

My 3.36 rear was kind of tired and I put in a fresher 3.55 rear.

I did a full rear suspension rebuild before I got to actually drive the car, and pretty much forgot that I did a gear change. Its not a very noticeable difference between the two gear sets.

3.55's. But if I already had 3.36's (I know that you don't in your situation) I'd stay with the 3.36's until I needed new gears.

He has 2.87 now.

Yes I understand that.

My point was that I have had both gear sets that he is considering, and it is an almost unnoticeable difference between the two gear sets he is choosing between.

wow - some great responses. That was what I was looking for. I think I'm going with the 3.54. Thanks :thumbs:

:iagree::lurk:

I think the 3.54 will increase your fun factor and that is what it is all about with these cars.