I am running a stock non posi 10 bolt rear end behind a GMPP crate 350/330 hp and Turbo 350 trans in my 68 Camaro.

I am running the stock 2:73 gears and am thinking of upgrading to an Eaton Posi and maybe 3:73 gears. The engine specs are below..
The car is definitly not getting the most out of this engine with the tall gear ratio.

Would this be too low a gear for this set up? I calculated that the engine would be turning about 4,000 rpm at 80 mph with the 3:73 gears. If not what would be an ideal gear ratio?

I plan on replacing the trans later when I get more funds to a Turbo 200 4R, or a 700 R4 overdrive.





http://www.sallee-chevrolet.com/ChevySmallBlockV8s/images/deluxe330ho350dynocurve.jpgHorsepower:330 @ 5000 RPMTorque:380 Ft. Lbs. @ 3800Max. Rec. RPM:5500Comp. Ratio:9.1:1Rocker Arms:10089648 1.5 ratio Crankshaft:14088527 Nodular cast iron.Connecting Rods:10108688 PM steel.Pistons:12361371 Cast Aluminum.Piston Rings:14089025Timing Chain:14087014Intake Valves:10241743 1.94”Exhaust Valves:12550901 1.50”Valve Lash:ZeroIgnition Timing:10 BTDC @ 700 RPMValve Springs:10212811 Block:10105123 Cast Iron 4 bolt main with 1-piece rear seal.Camshaft:24502476 Lift: .435” I, .460” E. Duration @ .050: 212° I, 222° ECylinder Heads:12558060 Cast Iron 64cc Vortec combustion chambers.Spark Plugs:R44TS Gap@.045 (300 HP 350), 41-932 Gap@.060 (330 HP 350). R44LTS Gap@.045 (330 HP 350).

It's a matter of preference. There is no "ideal" ratio. I run 3.23 behind my Muncie which is good for my purposes. I wouldn't be happy with 3.73 on the highway. Maybe you will be though.

Keeping it in the low 3's would be fine for the 350 trans, but not ideal for the 200 or 700 trans. In case of the later, the 3:73 would work out great. I run a 3:89 ratio with the 700 and the rpm range is fine.

I had a similar combo as you have now in my 69. I switched my rearend to a 12 bolt 3.55 posi. With the TH350 you will want to go the OD tranny as you will always feel you need one more gear on the highway. I am replacing mine this winter with the 700R4. You will then have to decide between the two tranny's with your 3.73. With those gears what I have read and searched the the 2004R might be a better choice than the 700R4. They say because of the 1st to 2nd gear spacing. Then you have to decide on the 2004R or 700R4 issues. There are a lot of posts on which is better(more HP) capable. Finding parts, cost of parts, whose doing the work, availability of older verses newer, etc... Keep in mind what your final set up is to be. Just street, some weekend drags, show. Aren't these cars fun!

I was leaning toward a 2004r as I do not want to modify/shorten my driveshaft..
I understand I can use a Turbo 400 trans crossmember for the 2004R..Has anyone had experience with this?

Bowtie Overdrives wants $175 for a crossmember, but I can buy a repop Turbo 400 crossmember from Classic Industries for about $65

The turbo 400 crossmember would have to be modified. The TH-400 only came with Big Blocks, so the transmission mounting plate is offset to the passenger side. Pontiac Firebirds had a TH-400 that was not offset. Most repro. houses sell the same crossmember for both, so make sure you measure it, no matter what they tell you