Blackwater
Engineering Geinus
I am new to this forum but I engineer for a living and teach what I engineer. I decided to upgrade my transmission due to me breaking it so many times. That and I plan on putting down some serious ponies under the hood. That's another post. I started looking at what transmission to go to. I seen the T56 but I felt like it was to long and I would have to cut a hold back of the original position. So, I decided to stick with just truck manuals. I studied the latest and greatest Manual truck transmission. It fell into the NV4500. Now I found that there was two RPO codes for this transmission. MT8 and a MW3. Now internally they are the same except the gear ratios. MW3 having closer ratios compared to the MT8. This is why I chose the MW3 over the MT8 for my half ton which the guys at the office call it the 5/8 ton. Its more than a half and less then a 3/4. Now on all New Venture manual the 4th and 5th gear ratios are the same. The gear ratios are different from 1st to 3rd between the two RPO's. MW3 has two bell housings for the traditional 58 model standard 6 bolt bell housing and the new LS series 9 bolt. Now your thinking that You cant mix either one. You can go from a standard 58 to a LS and the LS to the 58. This is true because they took the 58 standard bell housing and added one bolt at the top and two at the bottom of the 58 standard housing. I could have used a 93 through 98 bell-housing but I plan on dropping in a L92 therefore using all nine bolts. This will be needed for the 376CID (6.2) stroked 4 over to 418CID (6.8), polished and ported heads, larger cam, mid length headders, and 60lb/hr injectors on a Edelbrock cross-ram duel 90mm TB setup. Now to bolt it up and work with the old engine I used a 98 3500 clutch to match the old engine to the newer transmission. Later for the LS swap I will be using the 2004 3500 clutch. The NV3500 and NV4500 differences are in the housing and the size of the gears. The NV3500 has closer gears than the NV4500. Also the bigger barrings as well. For you Dodge Ram readers out there I will caution you not to tow in fifth gear cause eventually the gear moves and slips off its own shaft. GM version has added a bolt to it to prevent this. also note that both Dodge and GM NV3500 and NV4500 transmissions will not work with each other due to input and output shafts. But I think I read some where there was an adapter or shaft swap somewhere. I did not research to much in that since I felt satisfied with what I found in the GM version. With the worry of the fifth gear slipping off I felt between the two that the GM version with that add feature was the better pick. Now with the the upgrade on the half ton truck there was an issue with the drive shaft. The NV4500 4x2 version that I acquired had a fixed yoke on the tail shaft. So I looked for options to convert it to a slip yoke version. I found I could swap the tail shaft or a two piece set up. Both would cost $1500 more or less to do. But I also was thinking that I would have to upgrade the rear diff on this as well. I found a 14 bolt SF 9.5" ring diff with 373:1 from the local salvage yard. Being that my original diff was a 10 bolt SF 8.5" ring with 3.08:1 I noticed my fuel mileage was going from the Gov. rating of 16 mpg for that truck to much less. So, I looked into a possible overdrive system. I decided to add the Gear Vendors under/overdrive (Gearvendors.com). After doing the math I found when I am in O/D and kick in the GV it was like I changed the diff ratio from 3.73:1 to 2.92:1. Much better then original. I found with the engine at its peak tune (the factory stock 350 CID 5.7L engine) I got close to 19 mpg with a empty truck on the freeway at 65 mph. The ultimate test was when I moved my family from the SW to the mid west. I loaded a 8x24' car hauler with our possessions and hit the road. While on I 20 I wanted to see the limit of this truck. So after topping off in Pecos, TX I was going 70 in a 80 mph zone I dropped it into third with the GV on (3+) and floored it it climbed speed rapidly then shifted into fourth at 80 then as it was still climbing rapidly I noticed the trailer swaying and shut it off just before I reached 85. I was curious to know how much I weighed that I can gain speed that fast. I was thinking the whole rig weighed 8 to 9,000 pounds. I stopped in big spring to get weighed at the truck stop across the Holiday Inn on I20 and was surprised to find that the whole rig weighed 13,980 pounds without driver and passenger. Now thinking this is with a factory engine with 220hp 300lbs ft of tourqe, no mods and 230,000 miles on it peaked my thoughts on the LS swap I later want to do. So this ends the manual transmission findings on this 93 GMC upgrades. I hope this was educational to those wanting to keep a manual and beast it up. I hear the T56 is also able to move the shiftier to the inspection port with a few mods but its a close ratio transmission and intended for on the road use. The set up I have described turns a five speed into a ten. I never use first except for towing or needed grunt brute force. Therefore, second through fifth over is similar to the T56 gear ratios, but you have that I can pull that first. So when you decide to upgrade to a better transmission, ask yourself "what is the purpose of this build?" I feel the NV4500 swap with the gearvendors will make your tuck that versatile monster that I was looking for.
