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60over68400 · 10-27-2005, 05:22 PM

I'm wanting to put some 3.55's in my 8.2. I was wondering how driveable on the highway my car would be after putting them in? It would be through a turbo 400. I'm think I would be about 3000 RPMs @ like 70, is that a pretty good assumption? I almost would like to stick with something a little higher because I do drive it on the highway. Any help or suggestions would be greatly apprieciated thanks.

6t7gto · 10-27-2005, 05:33 PM

60over,
i took 3.55 out of my car and went with 2.56.
cruise the highway at 2200 rpm now.
check this out...
http://www.tciauto.com/tech_info/calculators.htm#7

david

Jeffzilla · 10-27-2005, 05:53 PM

I have 3.43 's in my 79 firebird behind a turbo 350 and it does just fine on the highway.

Formulabruce · 10-27-2005, 06:15 PM

I left the 3.42:1 rear and installed a bolt in 2004R with .67 4th gear and lock up converter
1700 at 55

cblandin · 10-27-2005, 06:43 PM

Here's the deal. Most of us are used to driving much newer vehicles and overdrive trannies have been around for a LONG time now. I find that my 3.23's are annoying in my 67 Bird as compared to any new car I own. This is exacerbated by the fact that I have a "nice" rumbly exhaust (as do most of us), which makes it even louder. Finally, add the rattles, creaks, and groans found in 35+ year old cars and it isn't exactly a Lexus ride. The RPM in my BMW at cruise isn't much different tht my Firebird, but my BMW is loads quieter, and has an extra 1000 rpm until redline. I've always said the biggest benefit to an overdrive tranny was never mileage - it was driving enjoyment. One question - what gears do you have in there now? Accelerate to 3000rpm and drive there for a while on the freeway - do you find that objectionable?

TR · 10-27-2005, 08:06 PM

Quote:

Originally Posted by cblandin

Here's the deal. Most of us are used to driving much newer vehicles and overdrive trannies have been around for a LONG time now. I find that my 3.23's are annoying in my 67 Bird as compared to any new car I own. This is exacerbated by the fact that I have a "nice" rumbly exhaust (as do most of us), which makes it even louder. Finally, add the rattles, creaks, and groans found in 35+ year old cars and it isn't exactly a Lexus ride. The RPM in my BMW at cruise isn't much different tht my Firebird, but my BMW is loads quieter, and has an extra 1000 rpm until redline. I've always said the biggest benefit to an overdrive tranny was never mileage - it was driving enjoyment. One question - what gears do you have in there now? Accelerate to 3000rpm and drive there for a while on the freeway - do you find that objectionable?

You've nailed it down dead-on. Time was, 3.55's were once universally considered an all-around good compromise between highway cruising and max acceleration. A good gear that a musclecar owner can live with in daily life.

Fast forward to having owned OD equipped cars since '85. Having our cake and eating it too. I put 4.10's in my 6-speed '94 Z28 and still turn barely 2000 RPM's @ 70 MPH. I drive my '70 Judge with 3.55's, and even around town at 45-50 MPH, I still instinctively attempt to shift it out of 4th into a non-existant 5th. Can't believe we used to consider this a compromise gear. A RA IV w/4.33's would be near insane on the highway.

BILTIT · 10-27-2005, 08:11 PM

My 3.73's and th350 amount to about 3400 rpm at 65-70mph (no speedo). Sure pulls hard when passing but always seem to run out of rpm before i am done? Go figure!

b-man · 10-27-2005, 08:24 PM

I had a set of 2.56 gears in my '64 Tempest, they came in it from the factory along with the 215-cube six and 2-speed auto. I kept them when I transplanted a 455/TH400 combo into it, absolutely wonderful on the highway. Here in So Cal if you can't maintain at least 75 to 80 MPH on the freeways for long distances you'll get run over.

After a few years the 2.56 gears gave up and I swapped in some 2.93 gears. Not long after the swap I was longing for those 2.56 gears.

My brother has a '69 350 Firebird that came with 2.78 gears. We swapped in a warmed-up 350 HO engine and changed to a 3.42 rear from a second-gen T/A. He said it was barely liveable on the highway.

In my opinion if the car is going to see any open-road miles 3.08s would be the lowest I'd consider. I would consider 3.23s to be right on the borderline, you'll definitely hate the 3.55s.

Formulabruce · 10-27-2005, 08:43 PM

Quote:

Originally Posted by cblandin

Here's the deal. Most of us are used to driving much newer vehicles and overdrive trannies have been around for a LONG time now. I find that my 3.23's are annoying in my 67 Bird as compared to any new car I own. This is exacerbated by the fact that I have a "nice" rumbly exhaust (as do most of us), which makes it even louder. Finally, add the rattles, creaks, and groans found in 35+ year old cars and it isn't exactly a Lexus ride. The RPM in my BMW at cruise isn't much different tht my Firebird, but my BMW is loads quieter, and has an extra 1000 rpm until redline. I've always said the biggest benefit to an overdrive tranny was never mileage - it was driving enjoyment. One question - what gears do you have in there now? Accelerate to 3000rpm and drive there for a while on the freeway - do you find that objectionable?

EXCELLENT POST!!!

2004R tranny HIGHEST ratio output auto ever made (89 T/A pace car, and many more had them) .67:1 output, then the lock up converter!!

Dryseals · 10-27-2005, 08:44 PM

My Corvette had the 2.73 gears and a 700R4, I swapped to 3.75 gears for the fun of it and have never looked back (275 40-17s). It sounds great on the highway.

The wifes street truck has 4.10 gears and a 700R4, a blast to drive and good manners on the highway (275-60-15s)

My 67 GTO had 3.90 gears and I loved the way it sounded cruising on the highway.

I just bought a 12 bolt posi with 3.55 gears for the 68 bird, 4 speed BW. I can't wait to here it roar.

If you like the engine noise and the sound of a good exhaust, go for it. If you want a quite ride, keep the gears down or buy a daily driver. I love the sound of a high reving motor, maybe thats why I'm looking at an older 911 for a work car. To each his own.

baron_ · 10-27-2005, 09:09 PM

i've got 3:55 in my '67 goat

i run 3100 or so going 65 mph on the highway
and by the time i'm doing 75, it's near 3500 or so...so that's definitely too much for extended periods

it's a little much (you'll have to drive 65)...but could be worse
a good compromise i think, unless you plan on doing a lot of highway driving

uforacing · 10-27-2005, 09:45 PM

Having done alot of driving with the 3.08-3.55 gears I will say one thing. if all you want to do is the "I" then 3.08 or lower or get a 200r4. Out here the Interstates are 75mph. I have driven the GTO with 3.55s 500 miles one way and I ran 65 with it.

One of the things I like is when im driving one of the cars to a event is that I am not in a hurry. I like driving the state routes thru the small towns and most of the speed limits are 65 or lower. Part of the fun is getting there.

Tripower455 · 10-27-2005, 09:51 PM

I have 4:11's in my 12 bolt, and turn 2800 rpm at 80..............with a Tremec!

marauder · 10-27-2005, 10:23 PM

I didn't like my 3.42 gears on the highway, around here the speed limit is 70 and everyone does 80. I installed a 7004R and now the 3.42s are just right.

carcrazy · 10-27-2005, 10:41 PM

Had 4.33's in a 67 GTO and it was pure misery on the hwy! I was in my mid 20's at the time and didn't care. Have 3.73's in one car now and I don't like that much either. 3.55's are probably borderline if you do a lot of highway driving. (damn I sound old)

David Jones · 10-27-2005, 10:41 PM

Mine has 3.55's and a Turbo 400 (400CI). 70mph is about 3200 rpm and the car will happily do that and more for as long as you can pump gas into it. Thats the way it was back "in the day". Its them damn loud ass mufflers most folks run that turd up a good highway run. My 20" Super Turbos keep it sane and quiet enough to listen to the radio (I never turn it on) or hold a normal conversation. I would go no further than a 3.23. Acceleration is to much fun.

form406 · 10-28-2005, 02:04 AM

i dont own my bird for modern cruising comfort...i own it for loud, adrenaline filled muscle car driving...no stereo(im a musician too)...the sound of the car is my music...

60over68400 · 10-28-2005, 03:09 AM

cool thanks for the input. I think I'll stay with what I got and get a new posi for it. How hard is it to install a 200R4 in my 68 bird or a 700R4, that would be cool. plus how much are each? 700R4 is probably pretty easy to find, but how about a 200R4?

Jeffzilla · 10-28-2005, 07:43 AM

Quote:

Originally Posted by form406

i dont own my bird for modern cruising comfort...i own it for loud, adrenaline filled muscle car driving...no stereo(im a musician too)...the sound of the car is my music...

I agree with him!

Junkyard Dog · 10-28-2005, 01:33 PM

I have 3.55 in my GTO. Not a highway gear.

I had 3.73, a four speed, and a 400 small block (Chevy) in a Camaro that I owned as a daily driver, took all the way across the USA in two days, and drove in Germany for 2 years . . .

Of course, that was in the 1980s, and I had never owned a car with overdrive. Even so, I sometimes wanted to shift up another gear whenever I was over 55 mph, even though there was not another gear.

I used to shift that car at 7,000 rpm when I was abusing it. In all, the 3.73 gear did not bother me back then, and I loved the acceleration. The car ran 12s without slicks, and I thought that was quite an accomplishment for a daily driver.

Now, 3.55 in my weekend car GTO seems really low when I am driving at highway speed.

I must be geting old . . .

I want a Tremec!

!

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