new ? which drive gear??

[k5floyd]

my truck has the blue 18 tooth drive gear and green 42 tooth driven gear. my truck originally had 31s and iirc 3.42 gears. i have since swapped to 4.56s gears and 35s. i have done some calculations on TCIs website and by my calculations i would need a 48 or 49 tooth driven gear to correct the speedo. BUT they dont have a 48 or 49 tooth driven gear. i think the highest one they have is 45. are there 48 or 49 tooth gears available somewhere else or from another company? i would like to avoid one of those little box things that hook up inline with the speedo cable. also if the 45 tooth gear is the highest i can get could someone tell how i could calculate how far off the speedo would be with it? and yeah i know its off by a percentage not a specific mph. thanks guys.

 

[dyeager535]

You might need to change the drive gear, along with the "sleeve" that holds it.

IIRC there are usually a couple of different ratios of drive gears, then a bunch of different driven ones.

 

[lectric80]

The way I figured out the Percentage that mile MPH was off was by measuring the distance between mile posts. So in my case with 33's and 3.08's I am off by 36%. On mine I turned .64 miles for every mile.

 

[k5floyd]

oh ok thanks. i think i try some more math and see what i come up with

 

[k5floyd]

ok i figured out what gear combo im gonna need. the 15 tooth grey drive gear and 41 tooth yellow driven gear. am i going to need a new "sleeve" for the driven gear? and what all is involved in changing out the drive gear? the drive gear is too easy.

 

[k5floyd]

hmm i guess i will give TCI a call and see what they say about this "sleeve" is. dyeager535, could you give me a better description or exlpanation of this sleeve so i can explain it to them. also the np208 uses the same gear as the 700r4 correct? thanks again

 

[dyeager535]

I'm not familiar with the t-case setups, on the auto trans (TH350, 400, 200-4R) GM had a piece that was clamped into the body of the transmission, and it's what the driven gear "rides" in. Also what the speedometer cable threads into. Depending on trans, but typically 2" circle as you view it, installed. Needed because the gear offsets were different depending on tooth count.

I don't have my parts manual, or I'd look for you and see what there was available. TCI will probably know though.

 

[k5floyd]

new problem, the drive gear i ordered is not the write design. i ordered a driven and a drive gear for a 700r4 trans wich the np208 is supposed to use. the drive gear is splined in the inside and slides onto the tailshaft. i need a 15 tooth drive gear which design does it use? i already talked to tci and they could not help becuase they dont know about tcases

 

[k5floyd]

ok so appearantly the drive gear is the same used on dodge 208s and supposedly the same style driven gear is used on nv4500 2wd trans behind a cummins or v10. now just stuck on where to find 15 tooth one.

 

[suntadz]

I have the excact same problem and setup. find out yet? I was about to rebuild my Tcase and all the info i find is 2wd application. I was thinking the drive gear was fixed and you can only change the driven on the tcase but not sure.