Need help on standard transmission/transfer case ideas.

[Mike_The_Grad]

Hey everyone, I'm working on a project for a potential customer and need some help with recommending a 4wd standard transmission and transfer case setup for him. He has a 1979 k10 SWB. It was his grandfather's and has a lot of sentimental value to him. He is doing a frame off restoration but keeping the old patina on the body. So far he has had the frame line-x coated and new leaf springs installed it's currently just a rolling frame. He had a custom ordered 383 stroker built already. So that is done and set. The truck was originally a stick shift and he wants to keep it that way. I believe the 383 is a roller block 1 piece rear main seal. Which means it's probably externally balanced. What are some options I can show him to help him settle on something he will be happy with and can keep the project rolling? So far I was thinking maybe nv4500 for the overdrive gear. But if that proves too complicated which 4 speed trans/transfer case would be suitable? I think the engine is making around 400 hp/unknown torque. Let's see what we can come up with.

[57taskforce]

Other than the obvious lack of over drive, any reason to discount the SM465/Np205 combo? They are a very stout unit. That 383 isn’t going to hurt it. The 4500 is a good one too, I would want a 205 behind it as well just because of how strong they are. A 4500 with factory GM transfer case isn’t going to work in a 67-72 because from the factory the transfer case front output drops on the wrong side. A transfer case swap will be necessary on a 4500.

[BLAZERMAN]

It would help to know what his plans are for the truck? If it's for cruising around town and car shows with just occasional highway driving would make a difference than if he plans on maybe pulling a trailer with.lots of highway driving. What size tires and gear ratios? I can drive these old trucks all day.long with 3:73 gears and 33" tires and be happy but someone else might need overdrive.

[mongocanfly]

Tire size and gear ratios need to be known..
I love my nv4500s, but I run rear gears in the 4s, downside to the nv4500 is they are getting harder to find which relates into $$$ as well
A higher gear ratio and a sm465 is a good combo..and these can be had for cheap

[Mike_The_Grad]

I like the suggestions so far. The guy has no budget really so he can afford whatever he wants. I dont know much about the guy. It's a square body pickup. Right now as it sits its stock gearing for 1979 SWB 4wd. I dont know what size tires he plans on running but I will try and find out. Also how he plans on driving the truck. I dont think he would be opposed to the sm465/np205 setup and may even be what he had in the truck to begin with. I will find out and report back.

[mongocanfly]

Next time I think I want to do another nv4500, I'm gonna look long and hard at a tremec tr4050..
that's another great option if he wants a od..and itll be all brand new

[Zoomad75]

The NV4500 is probably the best way to go to have a more modern feel to the shifting experience. 465's shift like dump trucks and the lack of OD really takes away from the driving experience. Even more so if the customer wants to hit the highway regularly.

So given that option, how to do it? There are 3 options for the clutch side of things. The nv4500 was always used with a hydraulic clutch setup. The aftermarket option would be to use an Advanced Adapter bellhousing and their clutch fork and adapter parts to use the later Squarebody style Hydraulic clutch master cylinder and slave cylinder. It's already engineered, but not cheap and still requires you to find a later hydraulic clutch pedal assembly to make the change. Those are getting harder to find, which is driving the price up. I'm seeing them go for $300 or more around here in Colorado. (you'll need it for all three options though, so factor it in regardless.) The AA setup works but the clutch linkage from the slave to the fork is hokey.

Option 2 is using an early GMT400 truck bellhousing with the 4500. The target range is 1988-1995. That setup still uses a slave cylinder that can be adapted to the stock squarebody master. The main difference is the 400 truck slave is on the passenger side of the bellhousing. Basically it's the opposite of the squarebody setup. The issue is the passenger side slave with no lift on the squarebody puts it in the path of the front driveshaft. A 4" suspension lift or a short body lift would clear the slave to the driveshaft. That bellhousing is more cost effective.

Option 3 is what I used on mine. I'm using a factory GM bellhousing from a 1996-1999 GMT400 truck. The change here is when GM changed the design of the clutch hydraulic system to an integrated slave/throwout bearing. There is no external slave or linkage to fool with. The integrated slave/bearing requires no adjustment. The newer slave/release bearing can be adapted to the stock squarebody clutch master cylinder with two fittings from Earls and a 36" -6 braided steel brake line. Mine works like butter.

Transfer cases are not limited to the ones GM used with the driver side drop. GM changed the mounting flange on the t-cases to a standard SAE round pattern with six studs with the 208 transfer case. 205's eventually got the same treatment and the 241's used in 89-91 also share the SAE 6 bolt mounting pattern. Keep in mind only the '89 241's have a gear-driven speedometer. The 90-91's used a VSS sensor for the electric speedo clusters those two years had. Any one of them will bolt right into an earlier squarebody. Though I would get the correct transmission mount cross-member that came with a 208 or 241 if you were going to use one of them.

Given it has that standard mounting pattern also means an Atlas II transfer case could be used.

[Second Series]

That’s some good information from Zoomad75.
I hope your customer keeps the original speedometer. The VSS was in some 1987 trucks. My ’88 has the 5LM60/NP241 with VSS. You have a couple options to keep the original speedometer. The mechanical option is to replace the tailshaft and rear housing. The article I saw was about converting an ’89 Blazer from mechanical to electric, but you could go the other way and get the parts from an ’89 Blazer or something else. The electrical option would be to use a converter box that uses the VSS signal to drive an electric motor to spin the speedometer cable. There are a couple companies that make these. Another option is to modify the original speedometer by putting a stepper motor in it, I’m not a fan of this mod but many people have done this. I decided to make my own and have a motor mounted to the back of the speedometer, not a trivial mod.

[1968 K20]

I went with the NV4500 and a NP241C. The NP24c passenger drop is getting hard to find. I am happy with the set up. The NV4500 is longer than the 465 so keep that in mind to make it fit.

[1968 K20]

I also used hydraulic clutch, made a bracket part of the booster bracket.

[Mike_The_Grad]

So it looks like the customer wants either a 3 speed or 4 speed standard transmission. And he plans on running 33"-34" tall tires and he said either 3.73 or 4.10 for the gearing. He plans on mainly cruising around town, occasional off-road but would like to tow as well.( I'm assuming toy hauler, camper, etc.)
I really dont know where to go with this now. Any help based on the info?

[57taskforce]

465/205 is my combo of choice for someone wanting a 3 speed or 4 speed.