MY-6 \ A833 to NV3500 Swap behind LS

[Drauka99]

Figured I would Post my project.

Background, I swapped in a 6.0 LQ4 into my 81 C-10. It had a 305 with a MY-6 3 speed with Overdrive manual behind it.
On the engine swap I kept the stock SBC engine placement with adapters and the manual clutch linkage. I used a Sachs NFW 1050 flywheel and a Sachs K187702 Clutch and pressure plate. I can not recommend this combination since my clutch went bye-bye after about 1 year of sporadic use. Measuring the carnage after pulling the trans I would say go with the Sachs NFW 1050 with a LUK 04902 RepSet. the Sachs clutch kit was 11" diameter and the LUK is 12" diameter, looking at the flywheel after removal, I wasn't getting much clutch contact to the flywheel, a good bit of the inner diameter of the clutch disk never touched the flywheel. That said there could have been several other reasons for early failure but that's my take.

Now I am swapping in a NV3500 out of a 89-93 C1500 (the S-10 versions are different and later models are different too, so I am trying to be specific).

Current parts List
Sachs NFW 1050 Flywheel (w/ ARP Flywheel bolts)
LUK RepSet 04-205 (w/ ARP pressure plate bolts)
Timken 614083 Throw Out Bearing
Dorman CS37815 Slave Cylinder
LUK LMC134 Clutch Master Cylinder
m12x1.0 to 3AN adapter fittings (straight fittings look like the will work but I also picked up a elbow adapter)
60" of AN3 braided brake line hose
Transmission Slip Yoke 3-3-5551X

The good so far. The MY6 and the NV3500 measure out to be the same overall length

The not so good so far.

The shifter for the Nv3500 is about 5" towards the engine than the MY6 and the MY6 shifter is offset about 3-4". I should be fine, from looking at other NV3500 swaps, for shifter space.

The 2wd MY6 is 27 spline (I think I did not count) output shaft. the NV3500 (see above about my specific make) has a 32 spline output shaft. The transmission mount is also about 7" rear of the one for the MY6. I have a 32 spline slip yoke ordered. I should be able to reuse the driveshaft I have with a adapter u-joint. I will verify but the caps currently look like 1310 Series and the 32 spline yoke is 1350 Series. If so a MOOG 348 should work. I have the transmission mount for the NV3500 ordered, the cross brace I can move back on the frame and drill new holes, I may have to make a spacer for the mount as well

 

[geardaddy]

the 1988-1990 is one design.(getrag)..././91-92 is another....and 1993 is the new venture design, by far the better of the 3....Retired New Venture distributor, had the "pleasure" of dealing with all of them design changes....

 

[Drauka99]

Transmission is mounted to the LS. The stock transmission crossmember for the MY6 fit the NV3500 and I was able to use some existing holes in the frame to mount it. I did have to cut off most of the part of the crossmember that wrapped up on the side of the frame since it was hitting the gas tank.

The driveshaft almost will mount back up. The larger yoke offset I think is the main culprit. I have a retired fabricator friend who still does a bit of odd jobs and he’s going to shorten the driveshaft a couple of inches so I have some rearmed travel allowance.

The master cylinder and slave cylinder seem to be just right so far. The 60” an3 line also appears to be the right length. Probably 3-4” more than needed in my case.

U-Joints ended up being Moog 348 and 369. The 369 fit the stock MY6 driveshaft to gm 10 bolt.

 

[496bb]

How did you like the MY6? I've thought about one of them behind a 292 straight six I have sitting. Not sure about the gear ratios and strength, the 292 will be very torque-y.

 

[Drauka99]

How did you like the MY6? I've thought about one of them behind a 292 straight six I have sitting. Not sure about the gear ratios and strength, the 292 will be very torque-y.

It was fine behind the 6.0. I think my whole list of issues came from the pressure plate mating to the LS flywheel and possibly the smaller clutch diameter I purchased. The nv3500 just went for a test drive and it’s worlds better engagement and general smoothness. I’m sure my MY6/MM7 needs rebuilt, if it’s like the rest of the truck it’s original to 1981 and by the odometer and the wear it’s seen a minimum of 130k, likely 230k.

 

[Drauka99]

Ok, all the parts fit, sort of, but more on that later. The clutch master cylinder mounted to the firewall over the speedometer hole. I made a small backing plate to stiffen the firewall some in that area. A 1-1”4 hole saw was about perfect. To mount the pushrod I made a plate that used the two mounting holes for the clutch pedal to the pivot bar. I made my plate out of some thicker metal we had laying around (a lawnmower blade). I made it sort of mailbox flag shaped, about 7” tall and 3” wide at the flag portion. The pushrod in my case fit right above the bend in the clutch pedal bar. I welded in a 3/8” bolt that was 1” long. Then used a washer and nut to capture the pushrod. The whole assembly in my case fit tightly to the back of the pedal bar and against the plate where the clutch return spring hooks.

The slave cylinder is where my issues came in. When bleeding the system we kept getting fluid and then losing it. I figured I had a bad master cylinder out of the box. BUT… what we ended up figuring out is the slave cylinder piston was full of air and the way the bleeder setup is on it it couldn’t be bled without working the piston by hand. We removed the hose and slave and basically bench bled that. Still no pedal. When we did some more testing we figured out that the rod on the slave cylinder was about 3/4” to short for my transmission, the rod was at the very end of travel and wasn’t working the throw out bearing arm enough. Luckily we had an adjustable rod from another project that fit.

Once we got that to the right length I took the truck for a quick test run and everything worked as it should, now I just need the post office to drop off my shift lever and I can put this truck back in the drive rotation.