OBS 4x4 nv3500 into NBS 4x4 Silverado

[adb5274.ab]

This is for anyone wanting to put a OBS 5 speed (newer internal slave cylinder style) into a NBS Silverado from my own experience.

The reason for this conversion was my desire for a 5 speed in my auto 99 Silverado 4x4 1500 and the limited availability and higher price of the proper NBS nv3500 in my area.

This was a very budget friendly swap, I have seen a few write ups where the older nv3500 tranny (external slave, clutch fork style) was mated to a LS1 motor where an extended throw-out bearing was used to compensate for the difference in bell housing depths from the OBS to the NBS trannys. Without a NBS nv3500 to compare to, I found that the OBS tranny bell housing was roughly about 0.25in-0.4in deeper. A few other very quick (rough) measurements showed that the difference in the input shaft are not really significant to the swap as far as the pilot bearing and clutch spines are concerned.

I used a 5 speed out and transfer case of a v6 97 Silverado (same tran mated to the 5.7 trucks) which had the internal slave cylinder in place of the original 4L60e in my truck. My truck is a 99 Silverado with the 4.8L motor (with a 5.3 motor sitting in my garage I am able to confidently confirm the crank shaft etc are the same with the auto 4.8 and 5.3 motors) so this swap would also work with the 5.3 version trucks as well.

I used a slave cylinder for the NBS 4.8 5 speed trucks. Reason being, the quick disconnect fittings on the clutch lines are located in different positions on the NBS vs the OBS trucks. The use of a NBS master cylinder was necessary do to the different (pedal to master cylinder) shaft lengths NBS vs OBS. The NBS shafts are longer and the quick disconnect fittings on the NBS hydraulic assemblies are found under the hood vs OBS which are down by the tranny. I had trouble finding the hydraulic line with the roll pin fitting on one side and quick disconnect fitting on the other for the master cylinder so I bought a steel braded line for a 2001 Camaro and it fit great (a little to long length wise but worked fine) with the same fittings as the trucks have.

A 4.8L 5 speed flywheel was used as well. A 5.7 fly wheel will not work on the NBS trucks. My clutch assembly is a early 90s style. I found that the older clutches are a little larger than the later 90s clutches and would allow more surface area of the clutch to the 4.8 flywheel. Id imagine a 4.8 clutch assembly would work but they are much more expensive (budget friendly swap).

The mounting of the pedal was a little tricky. After seeing where the mounting is supposed to be under the dash, I simply welded a few nuts to the bracket already present under the dash. It was a little awkward but worked fine for me. There maybe another way (use your imagination).

To compensate for the bell housing depth difference I just used two nuts as spacers behind the slave cylinder and bought longer bolts. these nuts (or in my case spacers) measured about 0.350in which turned out to be perfect. My clutch engages and disengages right in the middle of the travel of the clutch pedal.

The drive shaft from the OBS truck is also needed as well as the reverse light plug and speed sensor plug. The wires must be adapted to these plugs to regain your reverse lights and speedometer (I do not recall exactly which wires but it is not difficult to find out).

I used a pressure brake bleeder that I had from summit to bleed the clutch. I used an extra master cylinder reservoir cap and drilled a hole in the top to place a fitting in it to hook my pressure bleeder to. Bleeding the clutch was a little more tedious then I had expected but worked after I ran a couple quarts of dot3 fluid through it at 7-10psi on the bleeder.

I did not have the computer flashed for the swap but seems to be alright with the stock settings. Doesnt idle high or any other problems that I expected to experience. The truck will not start until the yellow and purple wires found on the original gear position sensor plug are tied together tricking the truck to think its in park so that it will start. These wires could also be tied into a clutch safety switch as well but I personally do not use those anyways (do to some tricky situations on steep hill start ups in the past wheeling in the woods in some of my other trucks). The speed sensor and 4x4 sensor also needed the plugs adapted to work (very easy)

here are some part numbers for anyone who would like to try this swap, the clutch came from auto zone about $120 I don't remember the exact diameter of it, 12in maybe? Also, the pedal came from my local auto parts dealer about $70.
Ill also include the bleeder I used, recommend it to anyone, it is a very useful tool I use mine all the time doing brake lines makes the job much quicker.

Hope this post helps ya out!


AUTO PARTS WAREHOUSE

Part #: W0133-1693892
Dorman Products
Dorman Products, Inc. is a leading supplier of automotive products and hardware to the automotive aftermarket. Clutch Slave Cylinder
Dorman
Qty: 1.00
Price: $ 79.95

Part #: S2NFW1050
SACHS FLYWHEEL, NEW -- A high quality flywheel; With 1-year Sach limited warranty. Flywheel
Sachs
Qty: 1.00
Price: $ 89.69

Part #: CE136.66013
CENTRIC CLUTCH MASTER CYLINDER -- 0.69 in. diameter, O-ring type port; Complete with reservoir, switch, and float; Offered in the original aluminum casting body design where applicable; Manufactured under the highest quality standards by OEM and OES manuf Clutch Master Cylinder
Centric
Qty: 1.00
Price: $ 41.43

Part #: TM302CC
TIMKEN ALTERNATOR PILOT BALL BEARING -- A high quality, direct fit OE replacement alternator pilot ball bearing. Pilot Bearing
Timken
Qty: 1.00
Price: $ 29.99


SUMMIT RACING

MCL-139212
Clutch Line, Hydraulic, Chevy, Camaro, Chevy, Small Block, LS1, Each
(Mfr. #: 139212)

MVP-0250
Power Brake Bleeder, 2 qt. Capacity, GM/Thread-On, Kit
(Mfr. #: 0250)

 

[NaturalGasForcedAir]

Good write up, thanks for the parts list at the end. The alternator bearing was used as the crank bearing spacer?

 

[adb5274.ab]

i'm not sure why it is listed as an "alternator bearing" in the description but no, it is actually the pilot bearing I used in the set up. It fit right into the larger opening at the end of the crankshaft. I have about 1k on this truck since the swap with no issues what so ever yet. However, I do plan to take it apart someday and replace the nuts I used for spacers behind the slave cylinder with a more legit spacer I will make at work on the burn table. The nuts were just a quick "trial and error" attempt I made because I wasn't exactly sure if the setup was going to work but it did. I would recommend anyone going on a similar route to this to make a spacer as well.

 

[reno124]

If you spent all the time and trouble to swap in a 5 speed why'd you not just get the nv4500?

 

[adb5274.ab]

had the nv3500 laying around and started brainstormin during the week so i ordered all the stuff I thought I would need and swapped it all on a Saturday. I only had about 4 hours into the swap plus another two hours into riggin up a clutch cap with a fitting to hook to my bleeder and bleeding the system. Like I said it was a budget project, bought the tran nd tcase for 200 and had another 400 into the rest of the new parts. Ive heard a lot about how the nv3500 is weak and would not hold up to the power of the nbs trucks but I havnt had a problem yet and have been beatin on it pretty hard. was well worth it, not a big fan of autos. If that tran grenades then ill look into the nv4500 but they harder to come by around here and much more $$$

 

[reno124]

I just picked one up for 500 bucks had another I found for 750 not sure where you're from but Texas has a good amount of them an make sure you've got the right fluid in it that'll do them in quickest and I understand budget builds my truck has a old sm465 in it right now cause I didnt have $ when the 3500 destroyed it self