I need some help identifying this trannie that I recetnly bought. I bought it under the assumption that it was an SM420. I took it apart and noticed that ALL the gears were straight cut and there is no synchro! Here are a few pictures:

http://www.pirate4x4.com/forum/attachment.php?s=&postid=461967

http://home.off-road.com/~md11fr8dog/Graphics/SM420GearSet.jpg

http://www.pirate4x4.com/forum/attachment.php?s=&postid=459978

http://www.pirate4x4.com/forum/attachment.php?s=&postid=459464

Its by diganosed as a 1940-47 GM truck trannie, part #185 by someone else. The seller still insists that its an SM420, stating he got it out of a '50 GM 1 1/2 ton truck. Any advice? Anyone ever seen an SM420 with ALL straight cut gears and no synchro?

Thanks

Doesn't look like a 420 to me. Certainly doesn't look like mine, but mine is a '67 model (last year).

not a 420 , but I don't know what it is.

I can't find any information regarding a complete non-syncro SM420. But I did find some information (and pics) about the SM420. Comparing the pics now...I don't think that is an SM420.

http://members.cox.net/cglabe1/SM420/sm420.html

Originally posted by GloNDark
http://members.cox.net/cglabe1/SM420/sm420.html

Glo, I was at Charlies house on Monday, I know what Charlie thinks!!:flipoff2: :flipoff2: ;)

He agrees, that its not an SM420. Too bad too, I got to see his 420 in action. Damn that sucka crawls. I can't imagine what the folks with 100-200:1 ratios are like!!:eek:

Originally posted by MD11Fr8Dog


Glo, I was at Charlies house on Monday, I know what Charlie thinks!!:flipoff2: :flipoff2: ;)

He agrees, that its not an SM420. Too bad too, I got to see his 420 in action. Damn that sucka crawls. I can't imagine what the folks with 100-200:1 ratios are like!!:eek:

hahaha I knew it was a small world but damn!!!

Hey if you want I can scope out the local pic-n-pull for you. I got mine there last July. Out of chevy camper/truck and I love it. Crawls great, stays in gear (Wow what a concept!;)) shifts throws are a little long but it's worth it.

OH another note, I stumped even the resident Chevy guy here at work. He has no idea what the hell that is. :confused: Sorry!! :D:D:D

Originally posted by GloNDark
OH another note, I stumped even the resident Chevy guy here at work. He has no idea what the hell that is. :confused: Sorry!! :D:D:D

Thanks Glo, I appreciate the offer. I have bead on a complete set up and will possibly work something out at Cruise Moab. Or I might just wait for the AA Rock Box and keep my 4sp!

In any case, I owe you a :beer: for the offer!!

BTW, your tube front is looking awesome!!:smokin:

Sean,
Whatever it is, it isn't an SM420, since the rear bearing retainer is way different. The 420 has 8 bolts and the tranny you have only uses 7. You won't be able to get any adaptor to bolt up to it.

The front counter shaft bearing (lower) on your antique is much larger diameter than on the 420.

<img src="http://members.cox.net/cglabe1/SM420/sm420_17.jpg">

Maybe it is actually worth something as an antique?

Charlie

Originally posted by Pin Head
The 420 has 8 bolts and the tranny you have only uses 7. You won't be able to get any adaptor to bolt up to it.

Good catch Charlie!! The evidence is piling up!!

[i] The seller still insists that its an SM420, stating he got it out of a '50 GM 1 1/2 ton truck.

Thanks [/B]

FIRST I would like to state that I am the one who sold the tranny to him..

SECOND I did not insist that it was a SM420 after he PM'd me the pictures and diagrams.. what I DID do is tell him what made me think it was a SM420


Third in a prior PM I told him that if it wasnt the right tranny to send it back and I would refund his money. here is a copy of both PM's



hy_desert_4wheeler wrote on 04-10-2002 01:16 PM:

yes I would like it reassembled.. It came out of a 50 model GMC 1 1/2 ton truck which only has the SM420 listed as being available for four speeds from 47 to 67 according to information I have found. also the picture at www.offroad.com/jeep/tech/convtrans/gm/gmsm420id.html appears to be the same to me..[quote]



[ quote]If you do not think it is a 420 then send it back and I will send you your money back..

Early 50's NP420 maybe? :confused:

It might not be a 420, but If I could find one like it local, it would go hella good behind that reverse rotation 283 w/ flipped axles. 50's GM trucks, huh? now ya got me lookin for one, would prob have to run divorced tcase, but I think the streight cut gears would live fine turnin backwards..... yea I know I should lay off the:smokin: and the dumb ideas.

Actually, straight cut gears are very strong and used in nascar transmissions (but with cone synchros). Depending on what material they and the shafts are made of and their strength processes they went through is another thing that WILL affect strength. Personally, I'd keep it as a cool-as-shit-paperweight and go find a more appropriate grindbox for the trails.

Originally posted by hy_desert_4wheeler


FIRST I would like to state that I am the one who sold the tranny to him..

SECOND I did not insist that it was a SM420 after he PM'd me the pictures and diagrams.. what I DID do is tell him what made me think it was a SM420


Third in a prior PM I told him that if it wasnt the right tranny to send it back and I would refund his money. here is a copy of both PM's




Hey Russ,

Welcome to the discussion. This wasn't meant to be, I apologize if it came across that way, a slam the seller discussion. I'm more interested in learning what the trannie is, cause IF it IS useable, I'd like to see it used by someone.

Also, for the record, Russ was most gracious in offering to refund my cabbage and to take the trannie back. I asked if he would like it back assembled or in pieces. Assembled was the request. I also noted that there wouldn't be any gaskets, but the case was power washed and the gears were all cleaned.

Here is another PM where I accepted his offer and offered him some more info why I DIDN'T think it was an SM420.

Anyway, Russ. If you thought I was trying to slam you, my bad. :emb: No intention on my part. I haven't even mentioned to anyone who I got the trannie from. I'd do business again if the opportunity presented itself. :beer: :beer: to you for being a stand up guy. Thanks!

______________________________________

Re: SM420



quote:
--------------------------------------------------------------------------------

hy_desert_4wheeler wrote on 04-10-2002 01:16 PM:

yes I would like it reassembled.. It came out of a 50 model GMC 1 1/2 ton truck which only has the SM420 listed as being available for four speeds from 47 to 67 according to information I have found. also the picture at www.offroad.com/jeep/tech/convtrans/gm/gmsm420id.html appears to be the same to me..

--------------------------------------------------------------------------------



No problem Russ. Just so you know, there won't be any gaskets, but the parts are all clean, incuding the rust that was on the gears.

Just because it came out of a 50 truck, doesn't make it a 50 trannie . Could have been swapped out, heck, that's what we're doing!! The case certainly looks like an SM420, but that wouldn't be surprising. Why reinvent the wheel. Can you find anyone that has ever seen an SM420 with straight cut gears and no sychro?

Check these gears out - all straight, no synchro - this sucker must whine like a mutha!

http://home.off-road.com/~md11fr8dog/Graphics/SM420GearSet.jpg

Look at the exploded view of the disassembly

http://www.pirate4x4.com/forum/attachment.php?s=&postid=459978

Looks very different than the SM420 manual exploded view(sorry for the large size, but it makes it easier to see)

Huge ass image deleted - SM420 parts diagram can be seen posted by Pin Head elsewhere on PBB
__________________
Sean
8/75 FJ-40 2F rebuild underway, "Antique Roadshow" SM 420 = 1940-47 Chev Trans w/straight cut gears. part# 185", SOA, and PS conversion, frame stripped down to tub only.
1/76 FJ-40 parts car
TLCA #11877

you might want to put the tranny back together and count the 1st gear ratio. There was an older version of the sm420 that had around an 8:1 1st gear ratio. making plate adapters is not all that tough at all.

I would look into it first..

Just checked my '63 and it has helical cut gears.

Might want to check w/ these folks http://www.stovebolt.com/bboard/cgi-bin/ultimatebb.cgi

I used that site to find my sm420, just don't tell them its going in a Jeep, they think we're all butchers :D

Originally posted by Jason M
you might want to put the tranny back together and count the 1st gear ratio. There was an older version of the sm420 that had around an 8:1 1st gear ratio. making plate adapters is not all that tough at all.

I would look into it first..

I planned on doing that! Who can make the adaptor for me??:confused:

Might make a good auxilary box in a dual tranny application, but I sure wouldn't want to shift an unsychronized tranny. That must really take some getting used to. My father in law has a '37 Chevy 1 1/2 ton truck. I wonder if it has the same tranny. I'll have to take a look. I'm also curious what the ratio is. Count the teeth and post what you find.

Originally posted by Grandpa Jeep
Count the teeth and post what you find.

Will do, I just won't get a chance until late April/early MAy. This darn job keeps getting in the way!!:mad:

Originally posted by CJ5-man
...just don't tell them its going in a Jeep,...

Yikes, no chance of that!!:flipoff2: ;)