1999silverado

I have a 1999 silverado 4wd with a 4.8l nv3500. i am not sure of the transfer case. I was thinking about doing a cam valve springs and the other supporting mods for a turbo my goal is 400whp. I was wondering what the best route would be for transmission and transfer case. I would drive the truck daily and do not plan to beat on it although get on it every once in a while. I have 3.55 in the rears and i am currently on 35s. thanks for reading.

dantheman1540

When I got my truck it originally had an NV3500 but it made terrible noises and didn’t like to go into 3rd after an aggressive 1-2 shift. After about a year and a half of dealing with it the clutch was about done and I swapped in an NV4500 from 2500 with a 6.0. It’s a direct bolt in swap for trucks that came factory with an NV3500 except you the reverse switch from the donor truck. I've beat the crap out of my NV4500 for about 2 years and 30k miles and I couldn't be happier! They are surprisingly cheap (Compared to a built 4L80) I bought a rebuilt one with clutch and flywheel from Midwest transmission.



As far as transfer case goes my truck has a NV261(Light Duty). Not sure if it’s the same since yours is a 99 but you can check by using a VIN decoder and looking in the tech specs section or looking for a tag on the T case (Mine was MIA)

Now I am using the factory T case still however I had it rebuilt when I did the transmission swap just as preventative maintenance. I haven’t ever had any issues with the T case and I do 4HI launches on the street as well as tow a 20 foot trailer loaded with mud toys through sugar sand.



I highly recommend gearing down to 4.10s or lower with the 35s.

1999silverado

thank you for the information I was thinking of going to 3.73 this way I can still get more than 12 mpg. If you dont mind me asking how much did your swap cost you an the trans that you got was it rebuilt to factory specs or was it built to take so more power.

dantheman1540

I believe I paid about $1300 for the Trans and that was without a core to return to them. Clutch and fly wheel where a couple hundred more but honestly don't remember exact prices.



I spoke to a tech guy at Midwest Trans before I ordered it and told him my eventual goal was 600hp+. He said the only upgrades are a bigger input/output shaft and cryogenically treated gear sets. However the NV4500 is seriously stout in stock trim and since our trucks weigh much less than the diesel and big block 3/4 and 1 ton trucks of the 90s that the NV4500 originally came from. The shaft upgrades and gear treatments are unnecessary. There was an issue with some NV4500s that came behind Cummins diesels in dodge trucks where the 5th gear nut would vibrate off. However in the GM variants that bolt up to our LS motors the 5th gear nut was not an issue. I have been beating the snot out of this thing since I put it in and the clutch still feels new.



If you do go with the NV4500 I wouldn't change rear gears just yet because the NV4500s 1st gear (5.61-1) is much lower than your NV3500s (4.02-1). In my truck I rarely use first gear on the street unless I'm towing.



As far as MPG goes I got about 12mpg with my bolt on 4.8 and now with my supercharger I get 10mpg all day every day except when towing which is about 7.



There are a few other guys on here running NV4500s that might chime in and I believe there is a few guys with bolt on 5.3s and 6.0s still sporting the NV3500.

1FastBrick

iTrader: (17)

With 35's you need at least 4.56 to be similar to a 3.42 gear ratio with stock tires.

_zebra

iTrader: (5)

but like dan said, the deep 1st will partly make up for that in stop/go stuff. it's still got a .73 OD like the 3500, so with 35s and a turbo, 4.11s or 4.30s would be a nice compromise.
i barely use 1st in my 3500 with 4.30s & 33s.

if you keep the 261 T-case, make sure you add a rub kit while it's apart to keep it from wearing a hole through the case. if you swap to a 241, i don't remember that being a problem.

i did talk to a couple techs at Joe Gibbs Racing a long time ago that said they kept the stock clutch/nv3500 in the supercharged 4.8 trucks because it did fine.
that said, the only reasons i didn't 4500 swap mine a couple years ago when my 200k mi stock trans started giving up was because 1) i'd already did 4.30s prepping for my cam, and 2) i was a month from moving & i didn't want to pull a 6k lb trailer across the country with it or have delays trying to do a custom job in a time crunch.

_zebra

iTrader: (5)

the higher ratio rears he goes with, the more he'll need that turbo to be spooled at 2000rpm given the little 4.8

dantheman1540

How is your new NV3500 treating you? Mine was awful when I got the truck but I've always wondered how a new one would sound and feel. Is it quiet?

_zebra

iTrader: (5)

it's a LOT quieter but not perfect, and they never were. adding an extra .5-.75qt of fluid (either by parking sideways on an incline, jacking up one side of the truck, or pouring through the shifter hole) always made a big difference, too.
definitely a lot tighter having a new one than a 200k unit with a worn input shaft & synchros... go figure.

but the rough 2-3 shift is still a thing & was just a design flaw. i either double-clutch it if i have to go fast from 1st - or - drive like a not-crazy person & just give it the extra second it likes.

i got to thinking about it the other day, actually, and had i had more time & rebuilt mine (only a couple hundred less than a new unit, which is why i just replaced it), i coulda looked into the feasibility of using the S10 1-2 gearset for a more normal DD ratio.

dantheman1540

Never knew about the S10 gear sets it would be nice to have a friendly 1st gear. But then again I like the granny low when I’m dragging my trailer through Florida’s finest sugar sand.



I remember a few years ago you mentioned something about the clutch fluid line having a restriction and that being the cause of the difficult third gear shift. Did you ever end up messing around with that?