I need to jump my learning curve a bit. I have a friend of a friend who is a really kick-butt tranny guy who does race and street manuals but I want to have some background and technical opinions before I tell him what to do. I also need some knowledge before I ask his opinion so I know what I'm talking about and can correctly convey what I want.
First tranny in question is a T56 for my 96 Impala SS. I have a TNET1247 viper T56 and the input shaft, front plate, and bored-out tailhousing to convert it for GM use. The tranny is brand new from the parts counter so it won't need internal parts, but I'm considering some shift modifications. Most new manual trannys don't seem to put much engineering into shift speed. They're more focused on keeping them quiet with helical gears and reliable with long-life synchros that don't do much for shift speed. The old-school way to speed up shifts was to use thinner oil, but the T56 takes ATF to start with so I don't have anywhere to go there. How can I speed up shifts? What are the trade-offs to those modifications? Synchro life? drivability?
Second vehicle is a 98 F150, 4.6L, 4x4. The 4R70 auto is showing its age and the ratios don't match up too well with the 3.45:1 rear and 33" tires. I could swap the gears to 4.11 or 3.90, but since its 4x4 the cost is pretty large to do both axles. The M5OD is the direct bolt-in with a bit better low gear ratios but I'm wondering what its practical torque/GVW limit is. I occasionally tow an 8000-lb GVW trailer (rarely over 6000 gross) on short local jaunts to haul a car or a load of firewood, and frequently tow a 3500-lb boat. I have also been considering a 5.4L upgrade or maybe even a 4BT cummins. Here is what I want... the 4r70 has a 2.80 first and .70 OD. 2.80 is not enough for 33" and 3.45s and it likes to lug in OD at anything under about 75 mph. M5OD is 3.90 first and .70 OD with a sensible 1-2 ratio change... meaning that 1st is an actual usable gear instead of a granny. So far the M5OD looks great on paper, but what about in the real world? Practical torque/GVW limit of M5OD-R2? Some sources list the M5OD as only up to 1996, is that right? Any other ideas for an easily adaptable, close ratio 5 or 6 speed non-granny with a sufficient torque capacity for my setup?
Also... 33" tires on an 8.8" IFS... your thoughts? I rarely do any off-roading. I didn't even really need 4x4, it just happened to be on the truck I found for the right price. But, I enjoy off roading and I don't want to snap stuff if I do decide to use it for its intended purpose.
