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If you want to go with a manual trans, the NV4500 has been used behind GM motors and with the NP205...Barrman has that setup with a 396 motor...there are a few threads on that.
If an auto, I would think the 700R4/4L60 or the newer 4L80 would be the choices...
For the cost of an OD tranny I bought a set of CUCV axles - just saying. The stock R&P is 5.87:1 and the CUCV axles are 4.56:1 - will bring the revs way down.
The t-case is divorced so it is relatively easy to swap out for a 205.
The T98 is a good strong transmission with a creeper gear & 1:1 in 4th. If new axles aren't in the picture Jon's recommendations are good. NV4500 for stick, 700R4 for Auto. If you are going that way then get a married 205 - 2 less u-joints to lube or fail.
FYI: Going to a 4.56 axle gear with a stock tire is the same as going to a 44 inch tall tire on a stock 5.87 axle...its a BIG move in ratio.
With everything stock at 65mph you have to turn 3770rpm. Switch to the 4.56 gears & you are down to 2929rpm.
Leave everything stock but add a .85 OD & the rpm only drops to 3205. I'm not that great with chebby transmissions but I think you can get the NV4500 with a .72 OD which will drop you down to 2714rpm.
Well heck, I've just talked myself into saying go with the NV4500/NP205 & leave the axles alone for now :) Unless you are going to thrash the pizz out of it or run monster tires that is.
Has anyone tried the synthetic gear lubes to see if that helped with the overheating?
Yes...no real difference noted.
Also moving the driveshaft from the passenger side output to the center has been done and didnt make a difference either.
I have done both and run a temp gauge and no improvement.
People have discussed going to 50W oil but I dont know of any test results from that yet.
Others have thought about a cooler and pump but the cost of a decent pump for gear oil and the plumbing and all involved seriously exceeds the cost of putting in an NP205.
Basically what it all amounts to, is this:
Either live with a truck that at 45-50 MPH is in its happy spot, or swap out the transfer case for a more modern and streetable unit.
I've mulled this over enough, that I can't see any better and more reasonably priced option than a NP205 to fix (not patch over) the limitations of the NP200.
thanks guys for all the info on the tranfer case i looked at the sticks and linkages they are tight
but id i drive it over 5 mph the tranfer case makes a noise not gear grinding but more of a popping noise
so i was told that most likely the baring is shot and it is poping the 4 drive in and out of i think that as you both said it is best to change it to a nv205
i do intend on driving it on the hwy what is your recomindation for a tranny
thanks once again
If its making popping noises at that low a speed, I would be concerned there is internal damage of some kind...
By the way, it an NP205...New Process did both the stock NP200 and the #1 upgrade you are looking for, the NP205.
History...the NP200 was first used in the M37 in 1950. It was designed for a flat head motor turning around 2700-2800 rpms. That is around 50 MPH in the M715 and the fastest the NP200 wants to be run without heat issues. The NP205 is actually the new, updated version of the NP200...came out in the early 70's. So changing from the NP200 t he NP205 is changing from the older, flathead version, t-case to the modern replacement for it.
In case it matters, the NP205 was used up to around 1 ton or a little more...there is also an NP202 that ws used in trucks of 1 1/2 ton and more...its basically a big NP205, a bit bigger all around but looks and works the same.
Thanks for the info