3.36 to 3.70 gears

**Rob79er** · 02-13-13, 12:00 PM

Will this have much of an effect on acceleration if I make this change? My car feels like it runs out of gear and is a dog off the line.
thanks

**mr.beachcomber** · 02-13-13, 12:34 PM

A little more information would be helpful. Are you running stock-size tires, undersized tires, or oversized tires? A 3.36 rearend ratio was common on C3's with a wide ratio 4-speed. Is that what you have? Has your engine been tuned recently? (Don't want to swap gears if a tune up is all that is needed.)

Both of my LT-1's came stock with a close ration 4-speed and 3.70 rearend gears and would smoke the tires coming off the line so swapping to a 3.70 should get you in the red zone a whole lot quicker, but your cruising RPM's are going to be much higher. (Here's a link to Summit Racing's gear ratio calculator that allows you to plug in your rearend ratio, tire diameter, chosen RPM, to obtain your MPH.) If you do have a wide ratio 4-speed, a better choice of ring and pinion gears would be the 3.55 ratio.

Hope this info helps!

**Rob79er** · 02-13-13, 05:42 PM

Yes- I have the stock tires size and Close Ratio 4 speed manual. Engine has been tuned.

**GTR1999** · 02-13-13, 09:01 PM

If you truely have a close ratio 4 speed then it will be a dog with a low torque sb and 336 gears. BB torque would drive it but the CR trans had a 2.20 first gear vs the 2.56 of the WR trans. CR trans are really a road racing trans setup to keep the RPM's "close" in the power band during up/down shifts. They were usally matched with a 370 or 411 rear gear. The WR was matched to a 336 gear in sb and 308 or 336 in BB cars. 79's didn't have BB so the question is do you have a CR Muncie as linked which was not offered in '79 or what should be a BW ST-10? You probably would have had to order the L82 to get it and I would be surprised if many were sold.
If you plan on changing you would be better off with a 373 over a 370 or 355 gear. The jump in RPM will be about 400 higher on the highway.

**SVO** · 02-13-13, 11:09 PM

Not sure how it affects the discussion, but if the OP has a '79 with the factory CR Super-T10, then it has a 2.43 first gear. If he has the factory WR Super T-10, then it has a 2.60 something first gear (don't remember the exact ratio). But the 2.43 close ratio box was only available with the L-82 engine and a 3:70 rear gear. There was also a third manual transmission option available with a deeper first gear and a 3:36 ratio only with the L-48 engine.