I bought an 85 GN unit and had it rebuilt with red alto parts and a kevlar band. I put in larger boost and reverse boost valves. It has a Sunnex super servo.

The motor is a 455, 9:1 compression with a 216/226 split @0.050 lift duration cam. .488 and 512 lift comes to mind. Don't remember the centerline. O4B intake with 7042251 carb.

The trans has a D5 converter still using lock-up. Behind this Olds, it feels too loose for my liking.

Looking to TCI Saturday Night Special as it might tighten it up some.

Thoughts and recommendations?

 

So do you have a tach to tell what its stall RPM is? If not, what do you want the stall RPM to be?

 

I have a hand held tac not one in the car. It has been a while since I really tried this out and need to revisit it. I believe I saw 2800 last time I tried it. I'd like to be in the 2200 - 2400 I think. This motor makes a lot of low end grunt that isn't being used.

 

You might want a heavy duty near stock replacement, maybe try a 2000 stall rating, it will probably stall well past that rating with your torque. The D5 is rated at 2400 stall and stalled around 2000 behind a 307 HO. The factory D9 low stall converter stalled at 1900 rpm behind a mild 350 and 403 for me.

 

Before going to a whole new converter and the price associated with it why not try a different ATF. Going to type F might help a little and I know ATI makes a Type F in 20 weight and also 30 weight. The 30 weight will lower the stall speed some. I doubt it will be 400 rpm like you want but could you live with 100 rpm lower?

 

I would want to see the pressure readings in each gear. It may not be the converter that is loose. A lot of torque is not generated by that engine when driving it or taking off normally. Of course, these transmissions shift real soft, in normal low power driving, and not harder like a 350 or 400 and that might give the feel of a loose converter softening the shifts when its just the way they are. My shifts are very fast, but I don't "feel them" in normal driving and no flaring of the rpms on the shifts.

 

The D5 converters in the GN and 442 supposedly stall around 2800 at full boost. I would imagine the mighty 307 would be a bit lower. I agree with the above post, I’d want to see pressure readings and a little detective work before condemning the converter. Those converters had to be tolerable to Grandma driving to church or Bingo. I wouldn’t think GM would sign off on a converter design that people would object to.