SM420 adapter from another era…looking for info (1 Viewer)

[39sandaV8]

Working on an old school SM420 Advance Adapters 2 1/4” plate adapter to a 3 speed case. Casting number is 1113. Transmission uses a replacement main shaft that has the LC 10 spline output. (Current one made by AA uses a longer adapter and an “extender” shaft that slides over the original SM420 main shaft).

Anyone have instructions laying around pertaining to this ancient setup? From what I understand, this setup was last available in the 80’s so I’m hoping one of you old timers has some good archives. There is, what appears to be, a 307(?) bearing in the adapter and the stock SM420 output bearing(?) in the rear of the transmission case that need to be replaced…so an old parts list might be nice to come across as well. The bearing in the adapter plate has an OD of 80mm, so it stands to reason that it’s a 307 but before I start tearing it apart I’d like to see if I can gather a little more information on this setup.

Also, the transfer case shifter setup would be nice to see too. The rig in question has numerous fabrications of dubious quality and design (definitely NOT designed by AA when baling wire and hunks of bed frame are used in the design). Any info or pictures you have would be helpful. Thanks!

 

[bsilva132]

I have that adapter on my rig. Bought it off another member many years ago. Mine was missing the lock but and AA was able to look it up in there system and get me the parts I needed. I would just call them and ask.

 

[CruisinGA]

After installing a SM420 in my FJ40 almost 20 years ago and recently swapping it out, I am not a huge SM420 fan. Just mentioning that in case you need to get into buying parts and lots of work to use it I would personally go a different route.

The site seems to be dead, but @Pin_Head did a fantastic SM420 writeup that I used when I installed one in mine. He gives measurements for a transfer case shifter adapter shown here. He also made a few of these adapters and sold them, I bought one and ran it for 20 years. Luckily the writeup is archived here:

sm420

Another shifter alternative would be to buy the AA twin stick kit but would have to do some work to set that up too. I now run those with the H42/split case I swapped in to replace the SM420.

 

[bikersmurf]

I considered that option back in the day.

The upside… crazy low first gear for crawling.

The downside… for daily driving it’s a 3 speed that shifts like a tractor.

AA twin stick configuration to shift.

I chose to keep a stock 4 speed with smoother shifting (and it’s what I already had).

 

[peesalot]

I have that in mine as well, behind a 6.0 ls now. I do have the instructions or a portion of them, I also have a spare adapter & mai n shaft that goes with it.
I see if I can find them and scam/pic so I can post or see if it has the bearing part#. There should be a spacer between that bearing in pic and the input gear IIRC ?

 

[White Stripe]

I have that in mine as well, behind a 6.0 ls now. I do have the instructions or a portion of them, I also have a spare adapter & mai n shaft that goes with it.
I see if I can find them and scam/pic so I can post or see if it has the bearing part#. There should be a spacer between that bearing in pic and the input gear IIRC ?

How is it with the 6.0?

 

[39sandaV8]

I have that in mine as well, behind a 6.0 ls now. I do have the instructions or a portion of them, I also have a spare adapter & mai n shaft that goes with it.
I see if I can find them and scam/pic so I can post or see if it has the bearing part#. There should be a spacer between that bearing in pic and the input gear IIRC ?

Any info would be appreciated. My main concern is the removal process on the rear bearing in the adapter. Looks like I should be able to remove the snap ring from the bearing and then pull the adapter off, but I don’t want to damage the adapter in the process.

 

[39sandaV8]

Here’s a look at what I’m playing with.

 

[peesalot]

No need to remove the bearing unless it is tight on the shaft, adapter should slide off with that bearing in place. Shifter, contact Georg at Valley Hybrids, The updated shift rail for front engagement has a much better attachment point.

Its is fine behind the 6.0. The spread bewtween 2nd & 3rd is the worst part. I drive it on the street quite a bit and it is not bad at all. When its in 4lo third gear is fun as heck as you can idle over rocks and hit the rev limiter when needed, makes for a fun trail ride.

 

[peesalot]

You know the bolts holding tcase to adapter that go into sm420 need to be cleaned & sealed & loctited as they pass through. Not all of them IIRC but the left side lower does. Check the helicoils, overtightening of tcase mount bolts can fubar the aluminum around the helicoil, I dont wanna say that adapter is a one time use but the helicoils need to be checked before hammering it back together IMO.

 

[39sandaV8]

No need to remove the bearing unless it is tight on the shaft, adapter should slide off with that bearing in place. Shifter, contact Georg at Valley Hybrids, The updated shift rail for front engagement has a much better attachment point.

Its is fine behind the 6.0. The spread bewtween 2nd & 3rd is the worst part. I drive it on the street quite a bit and it is not bad at all. When its in 4lo third gear is fun as heck as you can idle over rocks and hit the rev limiter when needed, makes for a fun trail ride.

The bearing in the adapter seems to be pressed on to the mainshaft..(definitely not budging)...the outer race spins within the adapter with some effort...so I'm guessing I should be able to remove the snap ring on the bearing and then remove the adapter so I can get a bearing puller on that bearing.

 

[39sandaV8]

You know the bolts holding tcase to adapter that go into sm420 need to be cleaned & sealed & loctited as they pass through. Not all of them IIRC but the left side lower does. Check the helicoils, overtightening of tcase mount bolts can fubar the aluminum around the helicoil, I dont wanna say that adapter is a one time use but the helicoils need to be checked before hammering it back together IMO.

Good advise! I am usually pretty meticulous about that anyways, but now I know to be ultra vigilant in that task. Thanks!