th400 to sm465 conversion

[jonessmc87]

Ok so i have a 89 v3500 with the th400/np205 combo. Bottom line is the trans is tired and runs hotter than hell even with two external coolers in combo with the radiator cooler.

I managed to pick up 2 complete setups sm465/np205 combos for 350$. I'm planning on doing the swap next weekend on my break from school. Question is, i know i need to change driveshaft lengths, not a big deal, but i already have a 4 inch lift in the truck and i had to make a 1.5in front driveshaft spacer for the lift.



My concern lies in the overall length of the sm465/np205 setup. The front driveshaft u joints are already borderline for my comfort when it comes to binding up when the truck flexes. I know the sm465 is shorter than the 400 and therefore a shorter tranny, moves the transfer case output towards the front of the truck, therefore making the front driveshaft steeper. if the combo is more than 1.5in (the length of my spacer) shorter than the 400 combo im concerned.

Could somebody measure the overall length of their sm465/205 combo from engine to bellhousing flange to center of rear output on the 205? I just want to put my mind at ease before i keep acquiring parts and get myself in a pickle during the swap.

o and any input/links to other swaps would be greatly appreciated. Thanks guys.

[BigRed76]

alright, the distance from the bellhousing (where it mounts to the block) to where the u-joint sits in the yoke on the t-case output shaft is 38" give or take a 1/4"...the front driveshaft is 25.5" from u-joint to u-joint (with the truck on the ground)...this is off of my stock '76 w/350, sm465, np205. hope this helps

[jonessmc87]

thanks alot bud. Mine appears to be 42, which means a 4 inch difference compared to your 38. This 4 inches minus my 1 inch drivehsaft spacer would put my front CV joint flange 3 inches further than where it is now, making it, in my opinion, impossible to achieve the angle i need for the 4 inch lift. This seems like im missing something because 4 inches isnt much and the sm465/205 combo isnt rare. I guess i'm gonna have to look into different front u joints. Have you or anybody heard of this problem with only a 4 inch lift? i've seen plenty of threads where 6 or 8 inch lifts get sketchy, but this is why i chose the four because it was gonna be simple and i would never have any driveline problems..........

[BigRed76]

I think you may have to just get a different front driveshaft because based on the pic of yours, the t-case end of it appears to be different from mine. My front drive shaft connects to the t-case by a u-joint & yoke, the same way as the diffs and the output shaft on the t-case. I dont know a lot about various chevy 4wd setups but that is what i do know.

You may also want to post this question in the 4x4 or suspension forums

[68 TT]

Originally Posted by BigRed76

I think you may have to just get a different front driveshaft because based on the pic of yours, the t-case end of it appears to be different from mine. My front drive shaft connects to the t-case by a u-joint & yoke, the same way as the diffs and the output shaft on the t-case. I dont know a lot about various chevy 4wd setups but that is what i do know.

You may also want to post this question in the 4x4 or suspension forums

^Mine is different than yours.

My 78 K20 SM465/NP205 has the same front output as the OP with the flat plate. I will measure it when I get home to make sure there aren't some differences in numbers.

[jonessmc87]

thanks alot guys, i posted it over int he 4x4 section too.

http://67-72chevytrucks.com/vboard/s...50#post4136850

[BigRed76]

Originally Posted by 68 TT

^Mine is different than yours.

My 78 K20 SM465/NP205 has the same front output as the OP with the flat plate. I will measure it when I get home to make sure there aren't some differences in numbers.

Mine is also a 1/2 ton though, so my driveshafts may be different from the 3/4 ton & 1 tons.