NV4500/NP241 Swap

[LeadFoot69]

I currently have an '80 K10 with a '90 TBI sbc mated to a SM465 manual/np205. Truck will soon have dana 60/ 14ff and 39" tires.

I was wanting to put in a five speed (NV4500) and a smoother t-case (np241) to make it a daily driver/weekend warrior. Im still debating on the t-case, but for sure the 4500.

Any help on putting together all the materials I would need? Please! Thanx

 

[Russell]

Are you planning to run a hydro clutch, or buy an advance adapter's bellhousing and retain the mechanical linkage? The good news is that the NV4500 uses the same clutch disc as your SM465, you will not need to change it out to complete the swap.

Either way, since the NV4500's shifter sits back a few inches as compared to the SM465, you will need to modify your floor pan to move the opening to account for the difference in location. Since the NV4500's shifter sits further back, you'll also run into clearance issues between the NP241 / NP208 shifter assembly and the NV4500's shifter boot.

To fix that, you can thread the linkage rod the rest of the way with a die and shorten the rod to allow you to move the NP241 shifter back a few inches as well. With a bench seat, you might find the shifter to be part way under the seat, but at least you'll be able to install a boot on the NV4500 that way. Since the t-case shifter is going to be sitting a bit further back, you'll also need to modify the floor pan to close up the NP205's original opening and cut for the NP241 shifter.

The wiring for the reverse lights is identical between the two transmissions, you can just plug and play. The t-case, on the other hand, is capable of turning on a 4x4 idiot light if you want to install one. The switch is just an on / off switch, so have it switch the ground and you'll be good to go. Also be aware that you'll have to get a transfer case from an 89 to retain your mechanical speedometer drive, and it must have a 32 spline input shaft to mate with the NV4500. The NP241 has a standard 6 bolt round t-case mounting pattern, and does not require any kind of adapters to bolt up to the transmission.

You will also need to purchase a new transmission / t-case crossmember. The NP205 has it's own type of mount and is not interchangeable with the newer NP241's mounting setup. As you might guess, your original drive shafts are no longer going to work. The 205 likely has a fixed yolk on it in your 80, and the NP241 has a slip yolk, not to mention the differences in length. You can simply pull the drive shafts from an 81+ K10 with an NP208 and any transmission and use them with the NV4500 / NP241 combo as GM standardized the drive shaft lengths by varying the length of the adapters between the transmission and t-case.

 

[LeadFoot69]

im not sure which clutch to use. Which would you prefer for daily use? hydro or mechanical? and i would like to stay away from expensive parts (AA bell housing). i have numerous vehicles to choose from, so finding a specific year and part is not a problem. i also have bucket seats, so no problem with altering the floor.

 

[Chevy305]

the type of clutch is pure preference. I like the feel of my mechanical while others will say that in heavy articulation the linkage can bind up. Hydro has a smoother pedal feel.

 

[Russell]

That, and hooking up a master cylinder can be a bit of a bother. You have to change out the pedal with one from a hydraulic clutch assembly, install the support bars, the master cylinder and then splice the line between the stock SM465 master & the NV4500 slave.

I retrofitted the matching 93 master cylinder to my truck, but it resulted in a VERY heavy pedal, much heavier than any mechanical clutch I've had in the past.

The AA bell housing isn't all that expensive anyways, less than 300 IIRC, and will save plenty of hassle.

 

[LeadFoot69]

so i would need the AA bell housing to have a mechanical clutch right? i wouldn't need another pedal assembly though to make everything work smoothly.

 

[Russell]

Yup, the NV4500 only ever came with hydraulic clutches from the factory. The earlier ones (93-95.5) have an external slave cylinder (also the lower first geared units) and the 95.5+ ones have an internal slave cylinder.

The AA bellhousing allows you to use the stock 1980 SM465 Z-bar clutch setup with the NV4500. The pedal feel will be just like the old 4 speed had.

 

[LeadFoot69]

cool. Thanx