TRNW-2: 6L80, Pump & bell housing machining

[pat schulte]

This is what mine look like when they come back from the machinist. I
believe he uses a lathe. I have used him for years and have always found
the work perfect, usually sets up between .0015-.002". He does machine all
3 surfaces.

On Thu, Sep 4, 2025 at 7:15 PM Chris Kershaw via trnw2 <trnw2 at trnw.net>
wrote:

> *Date:* Thu Sep 4 19:15:05 PDT 2025
> *Subject:* 6L80, Pump & bell housing machining
>
> Group, we have had some recent issues with machined 6l80 bell housings.
> I've had a few that would make pump noise under heavy throttle. Seems like
> it would happen once or twice and clear up after the initial 10-mile road
> test. I even pulled pans and inspected filters after 40-50 miles and no
> debris, so we let them go.
>
> Recently pulled a comeback out for noise and found the pocket depth was
> uneven, and the slide was tight in one area when checking clearance with a
> straight edge. Our local guy who originally machined it said the depth was
> off by .001 and fixed it. He machines them on a lathe. He does not cut the
> surface that contacts the case. I've noticed a lot of videos show these
> being cut on a milling machine.
>
> The Machined bells we have gotten from natpro or transtar appear to be cut
> with a milling machine and have a much smoother surface than lathe cut.
> They are also cut at the surface that contacts the case.
>
> Is there a machinist (I'm not one) reason to cut the bellhousings one way
> or the other or with one tool or the other? is it just personal preference?
> Any opinions or experiences on this would be appreciated.
>
> Chris Kershaw
> Kershaw Services Llc The Gear Box
> Mechanicsville, Maryland USA
> TRNW Member Since: 5/1/2023
>
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-- 
Pat Schulte
AAMCO Transmissions
Temecula, Ca.
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