The Stovebolt Site Forums The Shop Area Driveline NV4500 swap?

has anyone with a napco conv. 55-59 chevy truck ever swapped a NV4500 5 spd into them?

if so any threads with pics and good info available?

cheers

Nick

Are you planning to keep the spicer 23 transfer case?

I have not done a swap in a Napco, but I have done a swap in a 1959 gmc behind a 1959 pontiac 389, and another in a 1940 gmc with a 302 6 cylinder.

Getting back to your swap... 6 cylinder and v8 may make a difference in how you tackle the swap. You might be able to find a v8 bellhousing that is correct for the NV4500. The trick is to find one that bolts to the crossmember like original.

In both of my swaps, I used a 1994-1997 dodge 2wd nv4500. I used this version for 2 main reasons.

1. The pilot shaft is one inch longer than the gm version. This allows you to simply use an adapter plate that is 1 inch thick between the transmission and bellhousing. Most of the stock clutch linkage and components can be reused, including the clutch disc, pressure plate, and throwout bearing with some machining. A custom pilot bearing will be necessary.[NOTE 1: Advance Adapter sells an adapter plate, but further machining is required for it to bolt up to a stock bedllhousing. Either the bellhousing needs to be bored out to fit the plate, or the indexing lip on the plate needs to be turned down to fit the bellhousing.] [Note 2: There is a crossover throwour bearing that is available. If you would like to run a stock throwout bearing, the bearing retainer on the transmission will have to be machined down to fit the throwout bearing. This can be done on a metal cutting lathe.

2. The 94-97 dodge 2wd version can be made to work with a mechanical speedometer. In your case, the speedometer hooks up to the transfercase, so the speedo hookup isn't critical.

The early chevy nv4500 transmissions have the lowest 1st gear of 6.34:1. They also have a bellhousing bolt pattern that is unique to the early chevy NV4500, The Chevy 2wd NV4500 is shorter than the dodge 2wd NV4500. It may be possible to shorten the driveshaft from the transmission to the transfercase using the 2wd chevy transmission.

If you use any dodge 2wd NV4500, you will likely have to relocate the transfercase back, which means you will need to have work done on all 3 driveshafts.

The 4wd NV4500s are shorter than the 2wd units. They are intended to be married to the transfer case. I do not know if it is possible to bolt a yoke to the 4wd transmission and run a shaft from it to the transfer case. There are companies out there that sell adapters to bolt the NV4500 to numerous transfer cases. You would want a transfer case with a passenger drop if I remember correctly. I believe the 4wd NV4500 trucks used a Velocity sensor in the rear axle. I do not know if there is a speedo pinion gear in the newer transfer cases.

I found these sites to have some usefull information and/or parts.

http://www.high-impact.net/transmission_and_gear/nv4500.htm

http://www.novak-adapt.com/knowledge/nv4500.htm

www.advanceadapters.com/products/nv4500-transmissions

cool thanks for the info , the dana 23 will not be staying will be going with a dana 300 or atlas II.

Now with the dodge nv4500 you say a 1" spacer is used to make up the difference now does that make the tranny line up with the stock xmember? do you have any pics from your swap or anything like that for reference?

cheers

Nick

In my swap, The bellhousing sits on the crossmember. The bellhousing bolts down on 2 sides to the crossmember. The 2 bellhousing/crossmember mounts are the rear engine mounts. The adapter plate sits behind the bellhousing and crossmember. I had to make a cross member for a transmission tail support. The 4 speed sm420 I replaced just hung off the bellhousing with no other support. There was a carrier bearing and xmember that had to be removed behind the transmission.

I don't have many pics, and can't post them here. pm me with your email address, and I can send you a few pics.

I just noticed this post. I looked into the same transmission because I wanted to go faster at lower RPM, but wanted to keep everything else stock. It just won't work without modifications. I like the divorced Spicer t-case and didn't want to swap that out and then buy new drive shafts.

Since you are going with a different t-case, it seems like your best bet is to pull an entire power plant, transmission and t-case out of an 80's Blazer and just mock it in.

I think your biggest issue with this is that you still have drum brakes. You really don't want to be going 60-70 and having to stop in an emergency.

In the end, I am very happy I stuck with the SM420, but I can't go on the freeway, which is probably a good thing.

I would love to build another 55 with a complete modern drivetrain with disk brakes, that would be awesome. I think you should do this and ditch the NAPCO front axle and ship it to me!

To attach a GM 4500 to a 465 or 420 bellhousing, just make the retainer fit by boring out the bellhousing, making a spacer, turning down the retainer, or some combination. Mount the trans. up to the bellhousing off the engine, mark the existing bellhousing holes in the 4500 trans., drill and tap the new mounting holes in the front of the trans., make the bottom ones blind, or seal them up so you don't get a bath every time they are removed. If using a bellhousing w/o a bottom access hole, must mount the trans to the bellhousing before the engine.

Ed, if I understand your post, you are saying an sm420 bellhousing can be bored and redrilled to mount an NV4500 directly to it without an adapter plate. I'm not sure I agree or disagree with you. First generation chevy NV4500 transmissions have a 5.125 inch bearing retainer, and a mounting pattern that is unique to 1993-1995 chevy NV4500. This incarnation may work in the mannor you described. The rest of the NV4500 transmissions have a bearing retainer that is 5.60 inches. Cutting that much off a sm420 bell will put you close to the center of the clutch ball mount. The bearing retainer of an sm420 is 4.686 inches. Just something to consider. If you have mounted an NV4500 directly to a sm420 or sm465 bellhousing, I for one would definetely want details of what was done. The AA adapter plate costs around $300, and still needs machining to go on an sm420 bellhousing. I am open to new ideas.

Nick,
I'm still trying to find those pics in my hard drive

John

haha no prob john send em my way when you find em!

heres the specs on my build boys


Dana 60 = 5.13,ARB,Chromo Shafts, 35 spline outters, truss , reid racing knuckles.

14 bolt = 5.13, Detroit, Chromo 40 spline shafts prefer lol, truss, discs

Triangulated 4 Link Front and Rear with Johnny Joints and 1.75" DOM Links

nv4500/dana 300 or Atlas II if money/wife permits lol..

502 ram jet GM Performance Engine

15x14 32 bolt allied rockathon beadlocks with 42-46" Rubber

2.0 14" travel Coilovers havent decided on brand just yet

Dang, that is going to be a beast!

If you are going that far, why are you even worried about trying to fit anything to the original bellhousing? With that engine you will need to brace the frame anyway. Just weld in a new cross member for whatever super duty bellhousing that works? Use a hydraulic clutch and your good to go. Maybe I am missing something?

Do you have the original NAPCO front axle? Send me a private message if you want to sell the locking hubs. Need 1/2 ton off a 58-59.

Ain't nothing Napco about your truck. I agree with Jomichael. There is no need to use an original v8 bellhousing. My previous advice was based on the assumption of a more stock approach with original 6 or 8 cylinder, spicer transfer case, and Napco front axle. Your truck doesn't have any of those components. It still sounds like an interesting project.

John

THIS is what you are building!

Flying Chevy

haha the truck is a stock napco right now but wont be when im done with it yes. Im using a Advance Adapters bellhousing with hyd slave assembly etc. the motor has changed gonna go with a 650hp 540bbc