1FZ trans swaps 6R80 10R80 and more (5 Viewers)

[cruiserbrett]

Hello,

I have thought about this and run some numbers on clearances versus what Toyota designed in stock for the starter bolts.

The minor diameter of an M12 x 1.25 thread is 10.65 mm. Since these bolts are 70 mm long, the bolt will not be fully threaded and the portion under the head of the bolt will be run around 9.9 mm in diameter. This yields a nominal diameter difference for an M10 bolt passing through a threaded M12 x 1.25 hole of .75 mm. Radially this is .375 mm of clearance. Stock, Toyota had a 12 mm hole with and a M12 x 1.25 bolt with a major diameter in the range of 11.9 mm. This yields a diameter difference of 1.1 mm and a nominal radial clearance of .55 mm. There are three hole patterns to align. The holes in the starter, the block, and the adapter plate, with their own tolerance for location.

I think I am more comfortable with the larger radial clearance if we drill out to 13 mm and stay in the design range that Toyota came up with . The difference in radial clearance is not great, but I cannot do a full tolerance analysis for fit of the three hole patterns, as I do not know the tolerances that are held for the start or the block.

Thanks for the suggestion.

Mike

Very late to the party, but why not machine a relief on the transmission side of adapter to depth of the adjacent socket head cap screw, and put a stud in the starter, and use a nut on the stud?

 

[PIP]

I machine a bunch of transmission adapters. Some of them I've designed use Toyota starters. Several of these adapters use M10 studs through M12 threaded holes intended for a bolt from the transmission side. It works great, no problems whatsoever.