Machining Bell housing for S13/14 5 speed swap

[1976 280Z]

So, I've had a couple of 4 speed housings (now a total of 4) bell housings that I need to get machined to fit specs for a S13/S14 gear box.  The bell housing only changes in the main bearing size (increased), a shift rod diameter and the overall width around the face needs to be trimmed to a uniform 0.48" thickness.

 

• The 1 - 2 shift rod on the 71C was increased from 14mm to 16mm. The top shifter rod hole needs to be opened up to just over 16mm. I told the machinist to duplicate the hole in the 71C bell housing but later had to ream the hole slightly larger myself with an adjustable reamer because it was too tight.
• If you want to use the larger 71C counter shaft bearing like I did, you have to have the lower bearing hole increased from 56mm to 62mm. Again, the hole needs to be slightly over 62mm to allow the bearing to be a snug, slip fit.
• The counter shaft driven gear on the other hand, will contact the area around the bearing so this needs to be machined to reduce the thickness out to a diameter of about 3.5" or just remove the raised boss around the hole. The thickness in this area was .61"on the 71B, but only .48" on the 71C (about .13" difference). I had the machinist duplicate the 71C thickness (.48") out to just beyond the raised boss.

Details are here:

 

http://zhome.com/ZCMnL/tech/240SX5spd/transmission.htm

 

My issue:  I have not been able to find anyone in the Chicago or Detroit area who feels confident (and is reasonable $$).   Any tips of a good machine shop would be welcome.

 

Thanks,
Mike

[NewZed]

Which of the three operations are a problem?  The shift rod hole enlarging and the clearance work for the gear are fairly easy.  The enlargement of the bearing hole requires more accurate work.  If you swap to the smaller bearing, you don't need that.  Most machinists pause at the bearing hole work.  Xnke has a trick for that but may or may not share it.  

[1976 280Z]

Seems that it's not an easy set up - You're mostly machining surfaces well inside the bell housing and I'm being told that it's going to require several hours of set up, and some dedicated tooling, to do the machining.  Just want to know if there's anyone that's done this, has a machinist they trust, or a better place to start - particularly in my area.  If I can get a reasonable cost, there seems an interest for some people to do the upgrade.

 

Thanks,
Mike

[jeffer949]

When I did mine i had the machine shop do the bearing hole only.  I used a die grinder with a cut off wheel and a oval shaped bur to get the clearance for the gear. Just kept cutting till i had clearance.  On the shift rod I used a 5/8" drill bit and drilled it out. Just made it as square as possible and it followed the current hole. The only thing that needs to be done at the machine shop is the bearing hole. 

[NewZed]

I had an estimate of about $150 by a local shop that did mostly 4x4 off-road vehicle work.  Then I took it to a Porsche race shop and the machinist studied it for a while and was hesitant to even guess.  He noted that it was a very important bearing and would take precise and accurate work.

 

So I ended up swapping the bearing to the smaller one and will just replace the bearing more often if needed.  If you do it that way it's just one easy drilling/reaming operation on a small hole, and some quick, rough, material removal.

 

Some ballpark numbers and options for reference.  You don't get the benefits of the bigger bearing but Nissan probably made that change to extend 150,000 mile design life to 200,000.  It's not critical to performance of the transmission.

[280zex]

I also did the swap. I also had the same issues with finding some one to do the machining needed.

 

I got fed up, so I did all the work myself with a dremel tool and a few sanding drums. I used the sanding drums and a 9o deg adapter to clearance the inside of the case on the lower bearing inside surface. I then used the same sanding drum with out the 90 deg adapter to enlarge the 1/2 gear shifter rod hole. 

 

I also enlarged the secondary bearing hole to accept the larger bearing. I have the training for this type of machining work. Its not hard to do but it definitely needs to be done straight, and requires a specific tool. I have a nice adjustable reamer/4 stone hone, a gift from an old school machinist friend. A solid, long reach drill press is also required, but a Bullard 6ft horizontal, oil float machine works best.

 

you will need to cut the center section out of the trans brace, it needs to sit rearward about an inch. I used a miter box and a sawzall. I reinstalled the cut up trans brace, then i realigned and bolted it into place in the car. I then tac welded the pieces together. Then remove the trans brace from the car and weld it up solid.

 

This took me only 3.5 hours. This is not that hard of a job. You dont need to surface the secondary bearing hole for the larger bearing unless your going to have a lot of engine output torq. My turbo setup has 448ft lbs of torq so I did use the bigger bearing... 

Edited September 23, 2015 by 280zex

[Datsun_Z240]

I had an issue finding someone to machine my bellhousing too. Finally found a guy by word of mouth that was a machinist specializing in heavy duty diesel and marine. Ended up paying $200 and was done in 1 day. Everything was done with precision and accuracy. Maybe try calling some semi-truck shops.

[Hypertek]

good info thanks guys! 

[Tony D]

Wasn't someone in NorCal doing them for $150 each plus shipping?