Hi, I知 not sure if this is an engine or transmission question, and maybe a dumb one. I知 used to working with the 4 speed Muncie transmission and know that the first gear ratio is anywhere from a 220 (close ratio) to a 254 (wide radio) first gear as those cars had enough power to get the car moving, I知 now doing a 383 swap in a Camaro and noticed the first gear ratios are like 288 on a t56 or T5 transmission.Is this going to be too much first gear for a 435 hp 383 ?? Thanks

 

Depends on what rear gear you have and also which version of the T56 you have. I would assume you have the LT1 (Gen II, non LS, style) which typically 2.97:1, 2.07:1, 1.43:1, 1.00:1, 0.80:1, 0.62:1 forward, and 3.28:1 reverse. If I recall, first gear on the T5 is also around 2.97 or so (they varied between the years and world class vs non world class). The only "issue" I see is if you have the stock 2.73 rear gears. The 383 will move it just fine, although it will benefit from at least a 3.42 (gear that GM used when paired with the T56, or 3.08 with the T5).

 

I've had a stock T-5 behind a 405hp/406tq crate motor for 2 years now, 3.27 gears in the rear. It drives well, doesn't feel mismatched.

 

The 1st year LT1 T-56 in F body had those wide ratios. 94-up had something more like the old 4-speeds; 2.5x or 2.6x. Can't recall the exact #.

I put about a 96 or 97 one in my 83 car; one with the closer ratios. It has the weenie stock gears, just 3.73. (L69 car) 1st IMO is too high for that rear gear. I can't imagine what it would be like with even less gear. Furthermore, 6th is such a high ratio, that it's almost useless below about 70 mph. Engine RPM at that time (6th @ 70) is around 1750.

4.10 or even 4.56 would be a much better match for it. Larger CID will cover it up somewhat butt the engine RPMs are still arguably too low to be realistically efficient.

I also had 3.23s in that car for a time, while it still had the T-5, on one of the occasions I tore up the 3.73 rear. It was AWFUL. I'll never make that mistake again. The engine at that time was a 400, so that helped, butt it still was FAR less than ideal.

 

I have a magnum f w close ratios (2.66, 1.78, 1.30, 1:1, .80, .63). I have a 450hp 350 and a 9 inch w 4.11s. The ratios are perfect. I don't have any times/data but the car rips and the ratios are perfect. I can't say much about mileage cause I don't pay much attention. The same rear w a t5 sucked.

 

Why did the Muncie / 4 speed era have close ratios? A carburated engine cannot recover from a shift the way a fuel injected vehicle can. Also, if you look at torque curves of modern engines, a similar size / peak torque EFI engine has a broader torque curve. So the overcammed engines needed a lot of gear, and a smaller gear peexentage drop.

Go drive as many vehicles with both the 2.66 T56 / TR6060 and the 2.95 versions as you possibly can. Camaros, GTOs, C5, C6, CTS-V and experience it.

The third gen 3.73 and V8 T5 had great ratios together. You would be hard pressed to beat the 2.95 / 0.63 Magnum with a 3.73 rear. If your engine is cammed well without too mich, the 6th gear will be a pleasure to pull too. I am not a fan of the 2.66 ratios, but other people are. Hence, drive some yourself.

 

I dealt with this same issue last winter when I finally got my 5-yr project (LS376/480, T56 Magnum swapped 1991 Mustang coupe) on the road. I used the 3.08 geared Ford 8.8 rear end that came out of my '91 Mustang GT that I ordered brand new in 1991. The GT sustained a lot of saltwater air rust damage from when I used to live by the beach in north Florida. Anyway, the GT had the WC T5 with a 3.35 first gear. It was a good combination with the 3.08 rear gear ratio.

My T56 Magnum is the close ratio with a 2.66 first gear. When I got the LS swapped coupe on the road last November, the 2.66 first gear with the 3.08 rear gear felt like I was starting off in second gear. The engine has plenty of power but I had to slip the clutch and it wasn't fun to drive but boy did the car fly on the interstate in 6th gear! After driving the car like that for about three weeks, the car went up on my jackstands and I swapped the 3.08s for a set of Ford 3.55s. Now it's much, much better!