NP440/MY6 Swap Info

Discussion in 'Transmission & Driveline Topics' started by K1ng0011, Jun 23, 2017.

  1. AK99

    AK99 Member

    Messages:
    50
    Likes Received:
    5
    Joined:
    Feb 18, 2018
    Location:
    Lilly Chapel, Ohio
    The bellhousing with both bolt patterns was also used in many of the trucks with the common sm465 trans. This would apply to the '82-'87 years of trucks.
     
  2. Richard Schultz

    Richard Schultz Veteran Member

    Messages:
    303
    Likes Received:
    30
    Joined:
    Oct 8, 2018
    Location:
    Green River Wy
    My 79 nova has 3.08 gears,saginaw 4 speed.Will the shifter and rods work on the my6?Yes,the bell housing is the one Ive been looking for.Do you have this total package for the my6?
     
  3. K1ng0011

    K1ng0011 Veteran Member

    Messages:
    179
    Likes Received:
    26
    Joined:
    Mar 22, 2014
    Location:
    United States
    I dont think the saginaw 4 speed rods would mount to the np440 without modification. It might be possible to get a torch and bend them to make them fit. When I did this swap I had a variety of rods from different transmissions. I just found the ones that were close and seemed to fit and used a torch to heat them up and bent them to work. Spooge031 has more skill/experience and made some nice custom bent rods. If you get a np440 you need to figure out how you are going to mount the shifter to the tail shaft. Then you can figure out the rod length to the shift forks. But looking at the two pictures it looks like the reverse rod is the only shift fork in a different position. You will also have to clear the speedometer cable keep that in mind. Currently I still have the 4wd NP440 cast iron that is in the original pictures on the thread which needs rebuilt. I also have a 2wd mainshaft and another np440 bell housing. Needs rebuilt and a 2wd tailshaft housing. Hope this helps.

    Assuming 225x70R14
    Overall First Gear Ratio w/3.08: 9.5
    3rd Gear 60MPH: 2350RPM
    4th Gear 80MPH: 2290RPM

    NP440 Shift Levers
    NP440 Shift Levers.jpg

    Saginaw Shift Levers:
    saginaw shift levers.jpg
     
    mjgord51 likes this.
  4. Richard Schultz

    Richard Schultz Veteran Member

    Messages:
    303
    Likes Received:
    30
    Joined:
    Oct 8, 2018
    Location:
    Green River Wy
    Thanks.Im trying to convert to the my6.Im using a 4 speed saginaw now.My ITM stock shifter looks like it might work.Awhile back,a friend had a complete my6 set-up.He told me he would sell it to me for 200 dollars.Well he forgot and sold it.
     
    mjgord51 likes this.
  5. K1ng0011

    K1ng0011 Veteran Member

    Messages:
    179
    Likes Received:
    26
    Joined:
    Mar 22, 2014
    Location:
    United States
    So this is took me a long time of getting the money and gathering the parts but I was able to convert my 4wd model NP440 to 2wd and I wanted to share my experience and what I have learned. It's time for me to throw lots of information at you again. I did not take pictures of the whole rebuild process since someone has already documented that on another thread linked below. I did take a few key pictures so people can see some key differences like the 2wd vs 4wd mainshafts that are different. All 4wd cases are cast iron and all aluminum cases are 2wd from the factory. The only time you will see the cast iron case with a aluminum tailshaft is if someone has swapped the main case. I may not have touched on every single minor detail on a rebuild of one of these but hopefully this is a majority of what you need to know. If someone wants to use an internal hydraulic throwout bearing the information is below for you there. However, if someone decides to do this. I highly suggest you use an external slave cylinder. Like a universal one for a SMC 465 that bolts to the bellhousing. It should just be easier in the long run. This is two years in the making hopefully at some point if someone gets their hands on one of these transmissions it's helpful.

    Disassembly:

    1. Remove side cover
    2. Remove tailshaft housing bolts (snap ring also holding 2wd tailshaft on)
    3. Now you can access and knock out the countershaft rod it does have keyways remember when reinstalling.
    4. The countershaft can fall to the bottom of the case.
    5. Remove the front bearing retainer bolts and remove it from the front of the transmission
    6. Now the front input shaft and main shaft should both be able to come out. It will take some work to get them to slide apart from each other and get them out of the case.
    7. Now the the input shaft and main shaft are out you can remove the counter gear cluster
    8. Only thing left in the case is the reverse gear mechanism which can then be removed. I did not remove mine since it seemed to be in good shape.
    9. Remove the input shaft front bearing snap ring. Then remove the bearing with a press or some other method. I used some wedges and hammer to remove mine. ***On the outside of both bearings there is something that looks like snap ring. It is closer to one side of the bearing than the other. That has to be facing a certain way on both bearings when installed. Note this before removal I did not take pictures of the input shaft bearing. If you install them backwards you get to remove and reinstall the bearing(s) again like I did. ***
    10. The only thing pressed on the main shaft is the rear bearing retainer. You will remove a snap ring holding it on. Then you will need a press or some other method to remove. Again I used wedges and a hammer to remote mine.
    11. There are going to be several snap rings holding the gears, hubs and syncros on that you will remove.
    12. In the input shaft there will be needle bearings and in the countershaft there will be a lot of needle bearings.


    Assembly:

    1. Look at the forum post, pictures, and videos below on how to assemble the mainshaft. It will be easier since you already took it apart. The videos below will give you lots of little things to look for when assembling the transmission to find issues a normal DIY'er would likely overlook on assembly.
    2. When putting the rear bearing retainer on I used a metal tube the same diameter of the inner race on the mainshaft and input shaft bearings and hammered them both back on.
    3. Now that you have assembled the mainshaft and input shaft with all the snaprings, gears, hubs, and bearings time for the next step.
    4. I installed the needle bearings in the countershaft and input shaft using wheel bearing grease. Worked well for me. Watch the video below on a step by step on how to install needle bearings in the countershaft. If you use a good amount of grease the needle bearings will not fall out I had very little issues with them.
    5. Here on out it gets tricky when assembling everything. I could not get any other way to work than the following. There are two thrust washers for the countergear. They go inside the case on either side of the counter gear. I used a good amount of wheel bearing grease on both thrust washers that helped them "stick" to the inside of the main case. Drop the countershaft gear in the bottom of the case. Do not install the countershaft rod yet. Just let the countershaft gear sit in the bottom of the case and try and keep the thrust washers around the holes in the case.
    6. Put the input shaft in the front of the case.
    7. Feed in the mainshaft in from the back of the case and it will seat on the needle bearings on the input shaft.
    8. Now the fun part. Get a long screwdriver or something similar. Helps to flip the case upside down to have gravity assist you. You need to get the counter gear shaft in. There is very little clearance and those thrust washers will want to move around on you. You will use a screwdriver to get the hole in the case, the hole in the countershaft, and the thrust washer all lined up. Now feed the countershaft rod in one side. The hole in the countergear and the hole in the other side of the case will likely not be lined up. So the rod will not be able to go through the other side of the case. Use a screwdriver to work the countershaft gear and line up the hole in the countershaft gear and the case. Also hope your thrust washer has not moved around. This whole process is tricky and why I dedicated so much time to this part. You may ask yourself why I did not install the countershaft gear first. If you do that you will not be able to get the mainshaft in and line up with the input shaft. There gears are too large and there is not enough room in the case. If you have some trick on doing this that I do not know about post it to help others out. Make sure you install the keyways on the shaft for the countergear at each end of the case.
    9. Install the front bearing retainer. There is a groove in the bearing retainer and the case for fluid flow so make sure it's all installed properly.
    10. Install all orings in the side cover for the case before installing.
    11. Install the clip and speedometer gear.
    12. When installing a 2wd tail housing there is a snap ring you have to use the pliers to hold the snap ring over the rear bearing retainer as you push the tailhousing up to the case. Little tricky not that bad though. Then install the bolts in the tailhousing.
    13. There are two shift forks 1-2nd gear and 3rd-4th gear. One is shaped like a "C" there other is shaped like half a "C". 1st and 2nd is the half a "C" the 3rd and 4th is shaped like a full "C".
    14. Install the reverse spring and ball not sure of the official term for them.
    15. Installing the side cover can be tricky. I had to put the side cover so it was almost installed but I could see inside the case. Then I used a screwdriver to line up the detent springs and install the side cover bolts.
    16. The speedometer housing only goes in a certain way. So if you hook it up and get 0MPH from your speedometer you installed it incorrectly.

    Checking for gear hub engagement issues:
    Good video on the gear, hub, and synchro assembly and checking for bad syncros:
    Good video by a pro on looking for issues a DIY would probably never know to look for on a rebuild:
    How to install needle bearings in the countershaft:

    Rebuild Kits

    BK130 (No Synchronizers) $96 - https://transpartswarehouse.com/sta...ruck-np833-a833-transmission-rebuild-kit.html
    BK130WS (With Synchronizers) $101 - https://transpartswarehouse.com/sta...-np833-a833-transmission-rebuild-kit-594.html
    BK130WS DLX (With 4WD Countershaft not confirmed only read) $158 - https://transpartswarehouse.com/sta...ansmission-kit-3-spd-overdrive-my6-np833.html
    Note: the 2wd tailshaft bushing only comes in the DLX kit for some reason.

    Internal Hydraulic Throwout Bearing Parts

    3/8 Bellhousing to Block Spacer $90: https://www.summitracing.com/parts/qti-rm-6013/overview/
    1/4 Bellhousing to Block Spacer $43: https://www.summitracing.com/parts/icb-551820-250/overview/
    Extra Long Pilot Bearing (1.019) $15: https://www.speedwaymotors.com/Speedway-SBC-BBC-Chevy-V8-Extra-Long-Bronze-Pilot-Bushing,6974.html
    Standard Pilot Bearing Length (.750): https://www.rockauto.com/en/moreinfo.php?pk=593247&cc=1034895&jsn=544

    2wd Speedometer Housing Info

    I have not tried a 700R4 speedometer housing but from what I have read they should work. I have tried a TH400 speedometer housing an I do know that it works. As far as I am aware any 700R4 drive speedometer gear will work on this transmission.

    TH400 Speedometer Housing 34-39 Sleeve (Part #1362294):
    TH400 Speedometer Housing 40-45 Sleeve (Part #1362293):
    700R4 Speedometer Housing 34-39 Sleeve (Part #25512340):
    700R4 Speedometer Housing 40-45 Sleeve (Part #25512339):
    Stock NP440 2wd Speedometer Drive Gear 18 Tooth (Part# 8640518)
    Speedometer Drive Gear Retaining Clip Part #AC Delco 6261781
    Article On Speedometer Gears and Housings (Sleeves): https://chevellestuff.net/tech/speedo.htm
    Speedometer Gear Calculator: https://www.tciauto.com/speedometer-gear-calculator

    Thread on NP440 Rebuild

    NP440 Rebuild Thread: http://www.67-72chevytrucks.com/vboard/showthread.php?p=8372781#post8372781

    Bellhousings that Should Work

    SMC 465 Bellhousing External Hydraulic Slave Cylinder: Part# 15530202
    NP440 Bellhousing: Part# 14061655 & 14028936
    Bellhousing Bearing Retainer Size: 5.125"

    2wd Tailshaft Housings

    2WD Tailshaft TH350 Trans Mount Position Part #: C 15402 2
    2WD Tailshaft Th400 Trans Mount Position Part #: C15771-2


    2WD vs 4WD Mainshafts (2WD Bottom 4WD Top)

    [​IMG]
    [​IMG]

    Mainshaft Removed From Iron Case
    [​IMG]

    Cast Iron Case with 2wd Aluminum Tailshaft

    [​IMG]


    Gears
    upload_2019-8-20_12-6-59.png
    upload_2019-8-20_12-10-38.png
     

    Attached Files:

  6. Jeep43

    Jeep43 Veteran Member

    Messages:
    1,343
    Likes Received:
    53
    Joined:
    Mar 30, 1999
    Location:
    Connecticut
    I fooled with A833's in my past. The standard case was iron but they used aluminum in the 3+1 OD versions which are just mopar versions of what you used here. One weak point was the countershaft. In the iron case versions, the countershaft was a press fit into the case with a key. With the aluminum cased ones, they decided to float the countershaft into the alum case with no key. They also used shorter shaft which had less engagement so they could seal the oil with a whelch plug at the front (your pictures look like it has a plug showing not the end of a shaft). Over time the shaft would pound the case and slowly increased the shaft spacing.

    The fix was to bore the case to install steel bushings that restored the press fit with a regular countershaft.
     
  7. Richard Schultz

    Richard Schultz Veteran Member

    Messages:
    303
    Likes Received:
    30
    Joined:
    Oct 8, 2018
    Location:
    Green River Wy
    Im still looking for the my6 tranny like yours for my 79 nova,but I will use a standard throw out bearing.Now I use a saginaw 4 speed,with 3.08 gears.75 mph is 2800 rpms,using 205/75r14 tires,will soon go to 235/75r15.You will love this tranny.
     
  8. Richard Schultz

    Richard Schultz Veteran Member

    Messages:
    303
    Likes Received:
    30
    Joined:
    Oct 8, 2018
    Location:
    Green River Wy
    The tranny calls for atf,heard you can use 10w30 motor oil.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.