NP445 (4350) gear swap?

[Shmopar74]

I have a 74 w200 power wagon that has a built 360 with 430hp, high lift cam, 4 barrel, ect. Rolling with 35inch mud tires and 4.10 running gears, divorced NP 205 T-case. However, even though I have three times the ponies I had before, the NP445 doesn't have any more go-fast once I shift into 3rd. Do you guys know of work around for this issue that is contained to the transmission. I'm out of my depth when it comes to transmissions and was hoping someone had some advice. I was flirting with the idea of possibly swapping out 3rd and 4th gears with more desirable ratios. If this isn't possible maybe you guys could suggest a manual transmission that would serve my purposes?
Thanks for your time!

 

[91r/t]

I have a 78 powerwagon with the NP203 transfer case and the NP435 which has granny first gear. The complicated thing is the transfer case mate-up to the trans you pick. The two wheel drive trucks have it easy with a trans swap, but I haven't seen anyone swap out to an overdrive trans with a transfer case mate up. I think all the transmissions are a 1:1 4 gear (final drive gear) no matter what model (chevy, ford, dodge) they were used in, so not sure there's much around for swapping gears inside the trans to something that has overdrive or would act like one. I would assume you could go with a newer truck combo with the transfer case on it and then make mounts and drive shafts up that fit, but that seems like a hell of alot of work for a cruiser. I have 3.55's in my front and rear differentials and 33" tires and I hit about 31000RPM at 70MPH. Maybe swap the gears out in the diff's to get some more speed out of it?

 

[Moparpuller]

Bring it is a divorced case I would look I to an nv3500 or 4500 out of a 2wd truck. The np435 has the gears cast onto the counter shaft. There is a shop that makes custom straight cut gears but it is only for second and third and requires the gears to be machined off the stock shaft and re splined for the new gears