[TxFormula455]

Is a 3.73 in my car too much gear? I bought (rescued) the car from a guy who had aborted a restoration attempt. In the process he had a brand new 3.73 posi installed.

With my 455, 068 cam, turbo 400 with a 2k stall, does this sound like its a bit steep?

If so, what would you suggest for good gear to run? I'll be driving on the weekends only.

TxFormula

[screamingchief]

All depends on what tires you plan on running...

With a 275-60-15 out back it would be fine IMO.

Main thing to consider is that it is prefered that the cruise RPMs are higher than the stall RPMs,and obviously your good there.

Sooo,it wont be a "highway hauler",but should be ok as long as you are'nt using a tire much under a 27" dia. minimum.

Most 275-60-15's are appx. 27"-28" diameter.

Are you running A/C on it ?

Most will say something in the 3.23-3.55 neighborhood is best,and with a shorter tire I would agree (say 3.42 with a 26" or so tire).

[TxFormula455]

I've got 235/60r15's on now. Thats right at 26.1" I believe. They're junk tires, so I'll be getting new ones. I reckon a size up won't hurt anything, I've got plenty of fender clearance.

No A/C yet, but I've got everything short of the compressor - so that may be an option later.

275? thats a wide tire, ain't it? Dunno if my rims will hold that.... Howabout a 255/60r15?

TxFormula

[b-man]

I'd go 3.08, or 3.23 at the lowest.

A 3.73 gear with a 455 would be best suited for a drag racing-only car, street 455s especially with a mild cam like the 068 really don't need or want that much gear.

I ran a similar street combo, 455 +.030/068 cam/1.65 rockers/#66 heads (8.2:1 comp). Ran a TH400, Continental 13" converter and a 2.56 gear.

The car ran in the 13.80s with the 2.56s, slowed down a tad with a change to 2.93 gears. I was running a short 25.25" tire (235/45-17) so the gearing wasn't quite as tall as you'd think, 25.25" tire/2.56 gear being equal to a 27" tire with a 2.73 gear.

If you ever plan to drive on the freeway you'll hate any gear lower than a 3.23. HO Racing said in their catalog that one their favorite street combos was the 455/TH400/3.08. Good luck.

[P@blo]

I went from 3.08's to a 3.42 gear in my 400. I know it's not a 455 but they get on my nerves on road trips compared to the 3.08's. I'm with chief and B-man on this one, 3.08-3.23 would be a great choice. The 3.08's will be going back in for my next motor but the cam I have in my 400 needed more gear so I had no choice.

Plus the 3.08 will get you some better mileage too. Jim Hand has run a 3.31 gear down to the mid 11's in a 10:1 455 and a 041 cam at over 4000 lbs.

If you want to stick with the 3.73's you could always put a piece of tape over your tach and turn up the stereo when on the long trips. Just kidding bro but couldn't resist

[6D6GOAT]

at 65mph with a 27 inch tire you would be taching 3000 rpm. here is a good site to compare various combos....

http://www.angelfire.com/fl/procrastination/rear.html

[steve]

is 3000 rpm too high for a long highway cruise ? how long would you sustain 3000 before you got worried ???

[P@blo]

With shorter gears, you are running the motor at a higher RPM so wear will be increased. The trade off for that would be the better torque multiplication. Taller gears will run at a lower RPM but the engine will have to overcome a greater load and will have less torque to the rear wheels.

The main thing that I don't like about too short of a gear is the top end is limited and would hate the idea of getting passed by a Beretta or Neon RT on the way to the beach.

[steve]

yeah but if you have your ride set up right i think they would get the idea you are all about et's in the 1/4

[P@blo]

True enough Steve. If the track is your goal the sky would be the limit but have heard it is easy to over gear a 455.

[chiphead]

There's no such thing as too much gear, just not enough revvs. LOL

068 cam is really mild for a 455 with decent compression. If its a cruiser, 3.23 to 3.55 would be good. Go up in ratio for more interstate running, go down for more accel and track running.

[b-man]

I'd bet the car would be as quick with a 3.23 gear as it would be with the 3.73s, if not quicker. Putting a lot of gear in a street 455 is a waste of RPMs, more fuel used up and the engine gets worn out faster for no gain.

A 3.73 gear is what came in the '69 Z-28 with a high-winding 302. Your 455 doesn't need that much gear unless it's set up for the strip with a much bigger cam.

[steve]

the mystery of the best combo continues......

[screamingchief]

the mystery of the best combo continues......

No such thing IMO!

Every combo has some sort of compromise in it...

Nature of the beast.

You have to work with 'em,change things even a little bit,and further changes will likley be needed,it's an ever evolving process.

Even with unlimited funds it can be tough to be "perfect".

Often for many it comes down to a matter of "cost vs. return" for the final say.

And in that respect some things can wait till funds allow if absolutely need be.

Especially with "weekend cars"...

I was'nt that impressed by my '72 455 H-O GTO when it had the 068/performer/2000-2200 convertor/3.07 combo in it,,,it actually ran better with the 067/street dominator/stock convertor/3.07 combo in it,the shortblock had been replaced at some point in it's life,and it had the 067 cam in it when I first got it,so I decided to go with the "correct" H-O/068 cam and a performer (had issues with the H-O intake) to more closely emulate "stock" pieces.

Decided to go thru the engine after the tranny sheared the teeth off the rear ring gear in the th400,necessitating a trans rebuild,that is when the 068 was added,along with a "mild" convertor and new rear tires.

It was a heavy car (4000+),and the 067 obviously had more grunt down low,which was needed,but with the 068 it felt "lacking" that grunt,now had it had some more gear that likely would have been a whole other story.

The GTO wore 265-50-15's (25.5") originally with the 067 in it,then 255-60-15's (27") later when the 068 was added,so consider it also lost some effective gear ratio too,and I feel that greatly contributed to the "softer" feel of the 068 combo.

I had hoped the convertor would have helped some in that respect,but doubt that it did...

For that one (068/255-60-15) I'd bet the 3.55 would have been just about right.

But alas I had to part ways with it,got the "go-faster" bug and did'nt want to tear up such a rare car,in hindsight I likely should have just done what I wanted to with it...

[steve]

its a mystery to guys like me who havent had the opportunity to try many different set-ups for themselves and actually feel the changes............yet

[steve]

my car was originally set up with 4:11's and the guy i bought it from (who was a lot more ignorant than me) swapped them for 3.90...i wonder what perfomance was lost if the combo was truly set up right before...........

[matt1970pon]

well I had 3;23 in my 1970 lemans sport when I bought the car.I was a kid then just wanted to race the h@ll out of it.Got a 3;90 gear set in it.It was the worst thing I could of done.The car revs way to quick,can't cruise it,All the revs can't be good for the motor.To tell you the true I ran a 1998 corvette when I had when the 3;23 in it,didn't beat him but we were right next to each other,Till we both backed off at 145mph. Now With the 3;90 I ran a ws6 trans am maybe a 2001 Was with him till about 90 then he just walked away,bet I would have beat him with the 3;23.

[link09]

Hey TX, I have the same set up 455HO Ram air cam 3:73posi. Its a great street car but same thing I'm going to put a 3:08 or 3:23 in it this winter. Bad cruiser on the highway.

[Region Warrior]

Ok, i'll bring up a point that wasnt mentioned.
Lug'n an engine is harder on it then run'n alittle higher then desired rpm's.
You cant go wrong using 3.23-3.55 gears in just about anything Pontiac.
Another thing i like is taller/wider tires with 3.42-3.73's in my car's.
More meat to the pavement
The smallest cam i use is the 068 in a 400. The 744 in a 455.
I dont drive more then about .5 on highway's were i'm at.
Just be honest with yourself on how much hghwy vs around town you'l be driving and gear for that.

[matt1970pon]

well I had 3;23 in my 1970 lemans sport when I bought the car.I was a kid then just wanted to race the h@ll out of it.Got a 3;90 gear set in it.It was the worst thing I could of done.The car revs way to quick,can't cruise it,All the revs can't be good for the motor.To tell you the true I ran a 1998 corvette when I had when the 3;23 in it,didn't beat him but we were right next to each other,Till we both backed off at 145mph. Now With the 3;90 I ran a ws6 trans am maybe a 2001 Was with him till about 90 then he just walked away,bet I would have beat him with the 3;23.