Switch Pitch TH-400 (was something else)

Tue Jan 26 16:38:25 GMT 1999

If you don't mind I,ll pop in with my experience with my 82 Trans Am Turbo
350C  with lock up converter.  A lock up converter will 
fit on a regular turbo hydro but it wont operate in the lock up mode because
the 350C Trans has a small shaft inside the main 
splined shaft. The ECM sends voltage to a solenoid in the Trans and the
solenoid applies fluid to the small shaft pushing it out.
I cut the converter open to see how the lock up worked and found the shaft
pushes a drum with friction material on the outer
edge of the drum against the converter housing that is bolted to the
flywheel causing a lock up. The switch pitch converter has
a stator with the fins on pins that can rotate a fixed amount. Normal pitch
would be say 17 degrees. When you mash the throttle and hit the microswitch
a solenoid in the Trans puts fluid into the hollow input shaft into a
passage in the converter and into the stator
this moves the fins to a 30 degree pitch causing more torque multiplication.
At cruising speed you go back to the 17 degree pitch to save gas. I don't
know if the upshift dropped out the fluid to get back to the 17 degree or
not. Please note the degrees of pitch are for example only I don't recall
the exact numbers.                Don

> -----Original Message-----
> From:	Gwyn Reedy [SMTP:mgr at mgrcorp.com]
> Sent:	Tuesday, January 26, 1999 9:11 AM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	RE: Switch Pitch TH-400 (was something else)
> 
> Thanks for your response Max, and Shannen too.
> 
> Time to admit some ignorance. Haven't taken apart an automatic since I
> rebuilt a powerglide back in the 70's.  Have driven Buicks with Dynaflow,
> and a 66 Buick with 2 speed torque converter (my mom's car back then) and
> various TH350s and TH400s and the 4l60E in my Impala.
> 
> Was under the impression that you can't put a locking torque converter on
> a
> TH-350 or 400 because there is some kind of mechanical device (rod or
> sleeve) that is in the trans and activates the locking of the clutches in
> the converter. Seems like it would have to be that or else some kind of
> slip
> rings to get electricity into the converter to lock an electrical clutch.
> 
> So what I'm asking is if the mechanism to switch the variable pitch torque
> converter is similar enough to the mechanism of the locking torque
> converter
> to be used for the latter. Not concerned about how the decision to switch
> pitch or to lock comes about, but how does it get transmitted into the
> converter.
> 
> Reason for the interest: I have a big block pickup with TH-400 and 3.08
> rear
> end. 4l80's are very expensive but is what I'd really like to have. If I
> could get a locking converter to work on the truck I might spring for an
> aux
> overdrive unit to mount behind the automatic and put in a 4.11 rear.
> 
> Do you have a reference to a site or book that explains the variable pitch
> setup?
> 
> Gwyn Reedy
> Brandon, Florida
> mailto:mgr at mgrcorp.com
> 
> 
> > -----Original Message-----
> > From: owner-diy_efi at efi332.eng.ohio-state.edu
> > [mailto:owner-diy_efi at efi332.eng.ohio-state.edu]
> 
> On Behalf Of
> > Guenther,Max
> > Sent: Monday, January 25, 1999 1:05 PM
> > To: 'diy_efi at efi332.eng.ohio-state.edu'
> > Subject: RE: Switch Pitch TH-400 (was something else)
> >
> >
> > As for control I just used a cheap micro switch.  looked cheesy but
> > works great!
> >
> > >----------
> > >From: 	Shannen Durphey[SMTP:shannen at grolen.com]
> > >Reply To: 	diy_efi at efi332.eng.ohio-state.edu
> > >Sent: 	Monday, January 25, 1999 11:56 AM
> > >To: 	diy_efi at efi332.eng.ohio-state.edu
> > >Subject: 	Re: Switch Pitch TH-400 (was something else)
> > >
> > >Gwyn Reedy wrote:
> > >>
> > >> Coupla questions.
> > >>
> > >> Does any aftermarket vendor provide custom stall ratios on the
> variable
> > >> pitch converters?
> > >>
> > >At one time Kenne Bell did.  Looks like rebuilt/strengthened factory
> > >converters, two styles.  1800/2600 rpm, and 1600/2400 rpm stall
> > >speeds.
> > >Kenne Bell, 10743 Bell Court, Rancho Cucamonga, California 91730;
> > >(909) 941-6646.
> > >
> > >> What mechanism is used to control the pitch switch? Could that
> > be adapted
> > >>to
> > >> allow control of the clutch in a locking converter?
> > >>
> > >Old stuff, used in 65-67 Buick and Olds.  Mechanical switches close
> > >circuit, switches to high stall at idle, and at 70%+ throttle
> > >opening.  Electrically, it's opposite the TCC.  Original switches and
> > >linkage are tough to locate, might as well use a manual switch.
> > >
> > >> Gwyn Reedy
> > >> Brandon, Florida
> > >> mailto:mgr at mgrcorp.com
> > >>
> > >> > -----Original Message-----
> > >> > From: owner-diy_efi at efi332.eng.ohio-state.edu
> > >> > [mailto:owner-diy_efi at efi332.eng.ohio-state.edu]On Behalf Of Greg
> > >> > Hermann
> > >> > Sent: Sunday, January 24, 1999 10:50 PM
> > >> > To: diy_efi at efi332.eng.ohio-state.edu
> > >> > Subject: Re: DFI, Batch Fire, and other myths
> > >> >
> > >> >
> > >> >
> > >> > >
> > >> > >Was just thinking yesterday that the switch pitch converter
> > should be
> > >> > >connected to tcc control , and detent solenoid should remain
> manual
> > >> > >control.  BTW, 350 Buick HEI works, but must use drive gear from
> 455
> > >> > >points dizzy.
> > >> >
> > >> > Ahh--dangerous thoughts, and hardware that gets
> > forgotten--Anybody know
> > >>of
> > >> > any experience racing with switch pitch TH-400's????  Or
> > whether such an
> > >> > idea ever got tried with turbo motors??? :-) (Like switching
> > the pitch to
> > >> > let it rev up into the boost QUICKLY???)
> > >> >
> > >> > Regards, Greg
> > >> > >
> > >> > >Shannen
> > >> >
> > >> >
> > >
> > >
> >