Please re-assure me that I made the right decision on the gear change to 3:73's.. The gears are on my bench, but I haven't got them in yet, should I do a 3:55 instead???

Use is mostley city street driven, but looking for a wakeup to my current combo.. I try to do as little freeway driving as possable, but would like to be able to drive it at least 1.5 hrs @ at least 60 MPH... The current Combo,
Engine Code: TI03IIV / 7R117992
Casting #: 3902406
From: 1967 396 Impala

Heads: 3872702
From: 1965-1966 Closed Chamber (98cc)

Combo:

· 396 Bored .040 over
· 9.7 : 1 Compression
· 702 Heads with 3 angle grind, bronze guides, & hardened seats
· Speed Pro Forged Pistons (part # L-224ONF)
· Eagle SIR I Beam Rods
· Comp Cams XE274H-10 - .552 .555 / 230 236
· Comp K-kit (matching valve springs ect.)
· Harland Sharp Roller Rockers (1.7 Ratio)
· Holley 700 Double Pumper
· Performer RPM Intake
· GM HEI Distributor
· MSD 6AL Ignition Box
· Hooker Super Comp. Headers (with jet coating)
· Muncie M-20 Tranny / 3.08–12 bolt posi


Any help, or fedback is GREATLY appreciated..
~Scott

The 4 speed trans will love the 3.73. Good choice . I have a 3.70 gear set in my 9". You can run a taller tire if it turns out the gear is to low for your liking.

I had 3.73 in my 67. Yes it was good with the 4spd. I didnt like it on the freeway at 70mph. I went to 3.31, and enjoy the difference. At 70 Iam at 3000rpm, where I was at almost 4000rpm. before. Like ak69 stated, you could change to a different tire if necessary.

At 60-65, no problem. If you want run 70, maybe not a great idea. I run 3.73's with a 408 motor, 3000 stall converter and 275-60/15 tires. My '02 Silverado has 3.73's also with 265-70/17. I typically run the truck with the trans in tow mode, so overdrive doesn't even kick in until 65 or so. Pretty much every street car I have had over the years has ended up with 3.73's and I have ran everything from 3.08 to 4.56's. Always come back to a 3.73 gear.

Thnks for the replys, makes me feel ALOT better.. Anybody running 3.74's with an M-20?? I just want to make sure that I dont kill first gear by over gearing the rear end..

When I got the car, it had a Saginaw trans in it, the first gear was so steep that even with the 3.08's, first gear was almost non existant.. Not great for a motor that makes alot of it's power on the low end...

When I put the M-20 in it, it was painfully obvious that I over corrected the situation, & that the 3.08's had to go....

Man, I can't wait for this summer to see what this thing feels like with the new gears.. Also re-doing the rear suspention with new poly bushings.. Should tighten this car up pretty well..

Sorry to ramble, & thanks for the input..
~Scott graemlins/waving.gif

Originally posted by GRN69CHV:
At 60-65, no problem. If you want run 70, maybe not a great idea. I run 3.73's with a 408 motor, 3000 stall converter and 275-60/15 tires. My '02 Silverado has 3.73's also with 265-70/17. I typically run the truck with the trans in tow mode, so overdrive doesn't even kick in until 65 or so. Pretty much every street car I have had over the years has ended up with 3.73's and I have ran everything from 3.08 to 4.56's. Always come back to a 3.73 gear. Didn't think of that, my Yucon has 7.73's in it too.. I'll have to take a ride in tow mode...

Scott,I used to run 4.10 gear/M20 with a mild 396 using an LS6 cam..pretty fun gear combo IMHO
Your 3.73/M20 will be fine

Scott, when I did my rear end last winter I was set on using 3.55 but when I went to order they were more $$ than the 3.73 so I cheaped out. I now wish I would have put the 3.55's in. Its not real bad but mine is at about 3000rpm at 60. This is with a sbc and th350. The 3.73 really woke mine up and is great for the street but on the highway I would now prefer the 3.55's

Scott,

I agee with Blumont, if you plan on driving 1.5 hour or more, stay with the 355. 373 bring you up high enough in the rpms, to be a killer long distance. They are great for having fun, but without a five speed, they get old.

Fred.

Scott,

Either 3.55 ot 3.73 will work, all depends on what you want. In the old days, 3.73's were considered a highway gear. A stick car always got 3.90's+. With a 3.73 rear your M20 will have the effective first gear ratio of a M21/M22 with a 4.10. One thing to keep in mind is that there is no slippage to deal with in 4th gear with the stick. I run a 3000 converter with my 3.73, so like it or not, I am going down the highway at 3000 RPM most of the time. It's really not that bad, especially with the 3.76" stroke motors. The only other decently geared stick car I have been in lately is my cousin's 4.10 geared '66, but it also has a 30" tire under it effectively dropping the overall gear close to the equiv of my 3.73 with a 28" tire.

Disclaimer: JMHO - if you already have the gears and depending on if they can be returned or exchanged - put em in and run them. I would always rather error on the high side and then come back as opposed to wondering if I should have went bigger in the first place. Of course that's me, and I have been known to be a little eccentric with gears in the past [do you think 4.88's are too big to run in an 11/1 solid cam 355CI small block automatic '73 Vette??] kind of guy.

Thanks for all of the great input, although I'm still not sure about it, I am leaning twards sticking with the 73's.. I still have to get new tires, so maybe I'll just run a taller tire...

The gears are Richmond's, & I got them from Summit so returning them is not an issue (except for the 45 min. ride down).. However, I'm just not sure I will get the kick in the pants I'm looking for with the 3,55's...

What to do??? At least I have a couple of weeks to think it over (leaving for vacation on sat. graemlins/hurray.gif )..

Scott

I know my car is faster outta the hole with the 3.42's than the 4.10's with street tires. With the 3.42's it hooks much better, with the 4.10's it was as Cheech and Chong would say UP IN SMOKE. :D

i have 373 in my chevele what a gas bill wish i woulda kept my 323..

Oh ya forgot about THAT part!!!

See, now you got me thinking about the 3.55's again.... Although my car seems to hook pretty well with the crap tires that are on it....

Anybody know what the rpm would be with a 3.55 @ 65MPH ??? Would it be worth the loss off the line?? I want this thing to be quick on the street....

~Scott

Scott,what size tires are you running?

I think they are 28", but not sure.. They need replacing anyway (I'll look when I get home).. I can change them if I need to..

Scott

http://www.project33.com/tiresize.cfm Have a GREAT vacation!!!

Sal,
My Heavy Chevy has 3.73's in it. It made the 450 mile trip from Maryland to Boston many times back when I was driving it as a regular driver. Never had a lick of problem. Used to "race" my brother up the coast in his 73 Z-28, also with 3.73's every summer when we went north to visit relatives. Nothing like the sound of a nicely tuned engine spinning happily along at 3200 rpm for 7 hours smile.gif I say go for the gusto !

Thanks Bill, I think I'll go for it... graemlins/waving.gif graemlins/beers.gif