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th400 input shaft length?

2K views 7 replies 4 participants last post by  Hutch 
#1 ·
I need to know how long a stock input shaft is on a turbo 400. I was thinking of running a .250 thick aluminum mid plate, and I wanted to see if the trans I bought has a stock length shaft or a longer one. The length from the end to the pump seal will work.
Thanks
 
#3 ·
I plan on spacing the converter out, but I read somewhere that it is possible to change the input to a longer one, to accommodate a .250 thick mid plate.
I was worried that if this trans has a longer shaft and I space the converter, the input may be too deep and damage something. Is this something I should worry about? Or should I just space the converter and go?
Thanks,
 
#4 ·
You may have to send the converter back to the manufacturer and have it made for the 1/4" plate. You can space to a point to adjust clearance between the converter and flexplate but were only talking around .100" max . Usually a 1/4" of spacer will pull the pilot out of the back of the crankshaft. That pilot is important and aligns the converters centerline to the engine/transmission centerline.
I made a lot of input shafts in years past that were around .187" longer than stock for very high powered cars that used 1/4" to 5/16" midplates so that we had as much engagement into the turbine splines as possible. I make them standard length now as turbine spline materials have been improved.


Hutch
 
#6 ·
Hutch do you have a problem with the turbine not engaging into the turbine shaft properly?I always see a good witness mark on them.What type of machine are you making the input shaft on?Do you believe in removing 1 spline from the shaft ?What are your reasons for making it longer?
 
#8 ·
I had a problem with the shaft going all the way through the turbine spline as the converters were being made long for the midplates via the hub and not the cover. The shafts were solid and a good fit to the hub retained concentricity to the cover bushing and held the shaft dead nuts w/o the turbine bushing in place (T400).
I make the shafts on a lathe , hob the splines , heat treat , straighten then OD grind complete. The splines are made to the master spline T400 ring gear with a .999" OD.
No I don't remove 1 spline , I would rather not have pressure opposing that area.


Hutch
 
#7 ·
Just take your existing converter and push it clear back into the pump. Measure the distance from the mount pads to the flex plate. You need to add spacers to take that measurement down to 1/8" min to 3/16" max. At the same time look and see if the pilot on the converter is engaging the crankshaft bore. It need to engage sufficiently to stay concentric. What I've done on a converter built for no midplate (pre screw-on/tap-on pilot extension days) was to machine a ring to heliarc tack in place to extend the pilot so it engaged the crank. I'd prefer to see it in there 1/4" or so to be safe. You can make a ring and then simply hose clamp it onto the converter and TIG it in five or six spots around the ID so it's centered up. It needs to have an OD of 1.700" to 1.703" and the ID can be done up around 1.250" or so. Obviously length depends on what your setup requires. Just be cautious when welding.
 
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