66 Transmission Questions

[sackracing]

Just bought a 66', 250 I6 with a 4 speed.
Shift pattern is R all the way to the right and down, which trans would that be?

Any recommendations on an aftermarket shifter? Or can the factory one be rebuilt? It's super sloppy.

Thanks

[chevylookin]

cast iron granny geared SM420

[sackracing]

Thx

[61K10]

reverse all the way to the right and down would be a 465

[sackracing]

Either uses the same shifter don't they?

[Classic v6 GMC's]

Could also be the NP435

[Captainfab]

With Reverse in that position it is either a SM435 or SM465. No such thing as an aftermarket shifter for either of those. You will have to remove the shifter from the top of the trans and see what may be loose.

[sackracing]

I found the Novak replacement shifter. Ordered one yesterday.
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[padresag]

that may not repair your problem though. that sloppiness comes from wear in the trans. all that wear is accumulative from over a 50 year span. the bottom of the shifter may have some wear, but that is just part of it. the piece it sits in will have wear as well as the piece it connects to.
it is more than likely time for a bearing and seal overhaul which is not that expensive. gives you a chance to replace the washers and that will effect end play. it also give you the opportunity to check the rest of the shifter mechanism for wear
that shifter was also not a tight precision fit when it was new
ron

[sackracing]

I'm a dumbass, reverse is to driver and down.

[jrthe1]

I do not want to steal the thread but mine is to driver and up. Since the topic is 66 transmission, any one know what mine is as well?

Thanks.

[Captainfab]

Is it a 3 speed or a 4 speed? It sounds like a car 4 speed trans. I'm not sure about a Saginaw 4 speed, but with a Muncie or a BW T10, reverse is to the left and forward.

Originally Posted by jrthe1

I do not want to steal the thread but mine is to driver and up. Since the topic is 66 transmission, any one know what mine is as well?

Thanks.

[jrthe1]

Thanks Captainfab. It's a 4 speed and I'd love it to be a Muncie but PO said it was a Saginaw. Just trying to confirm and it seems that shift pattern alone will not tell the whole story.

[sackracing]

I'm guessing mine is a SM420, has bulldog first gear

[Captainfab]

If the trans is cast iron and has all 3 shift levers on the side cover, then it is likely a Saginaw 4 speed. It has been so long since I have driven a Saginaw 4 speed, I just could not remember for sure where reverse was.

Originally Posted by jrthe1

Thanks Captainfab. It's a 4 speed and I'd love it to be a Muncie but PO said it was a Saginaw. Just trying to confirm and it seems that shift pattern alone will not tell the whole story.

[61K10]

they are the same as the t-10 and muncie.

[sackracing]

Took the shifter out last night. It's broken loose at the ball, and the bottom piece has plenty of slop and broken welds where someone had welded it at the bottom before.

[chevylookin]

Not exactly sure what youre looking for but, sheesh! What you have explained sounds gnarly. These trans are damn near indestructible. Sounds like a PO has gone and fubar'd some stuff on you. Send us some pics of the damage so we can get a better understanding of exactly how bad your dilema is. Meanwhile, I found this on ehay:http://m.ebay.com/itm/Black-Painted-...257Ciid%253A18

Also, I did a search for sm420 (we have determined you are sm420 for sure?) all over Craigslist for the old cast 420. Nothing really going on nationwide. I did it for sm465 and it revealed many potentials around you within half a days driving distance. Maybe someone can chime in on me and tell us if the sm465 is a direct replacement for the 420 or do you need to adjust or cut things like driveshafts or the such. Good luck.

[sackracing]

Trans is working fine. Shifter was just shot.
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[sackracing]

That shifter in the eBay posting is the one it had on it. I got a one piece replacement shifter from Novak.
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