SM420 Slipping and Shop Recommendation (1 Viewer)

[FJCowboy]

Good Evening All,

I'm currently running an SM420 and Orion transfer case in my '69ish with 2F. It is slipping out of 2nd gear quite a bit and notice it mostly when there is not any torque on the motor, i.e. going downhill, but it will slip out going uphill as well. It will slip out of 3rd every now and then under the same scenario, no torque. Just within the last few weeks, I have noticed that it grinds a bit going into 4th as if I didn't have the clutch in all the way, but I'm pretty sure I had it pegged to the floor. I was hoping we were going to have a tech day/club meeting to meet you all in-person and pick your brains but figured I might as well throw it up on here and start the conversation. All of this to say, I'm guessing the synchros are bad and the SM420 could use an overhaul. I don't have the skills and probably would be best served to take it to a local shop. I read through numerous postings and from what I can tell County Transmission in Vienna and @OTRAMM are my best bets. I'm in Reston, so Vienna would be easiest, but I'm open to suggestions on what might be going on as well as recommendations for someone to repair it. The second part of the question is, I've considered swapping out for an H55F as well. Do I look into rebuilding the SM420 or look to invest in an H55F? Primarily local weekend driving and driving to wheeling spots between PA and NC. Thanks in advance.

 

[bkfj40]

What’s your budget?

 

[FJCowboy]

What’s your budget?

I recognize the SM420 rebuild is in the hundreds ($400?) and the H55F in the thousands ($4-5K?). I would love to work with someone and learn how to do it myself. My understanding of the SM420 & Orion combo is a really strong set up at least per some older posts. Pending cost, I would be willing to do the rebuild now and then look to do the H55F down the road. Even further down the road, I think I would consider an R2.8. I know big dreams, but have to have something to look forward to.

I also should have added Land Cruiser Heaven (@FloridaFJ80) as an option as well.

 

[Stumpalama]

I recognize the SM420 rebuild is in the hundreds ($400?) and the H55F in the thousands ($4-5K?). I would love to work with someone and learn how to do it myself. My understanding of the SM420 & Orion combo is a really strong set up at least per some older posts. Pending cost, I would be willing to do the rebuild now and then look to do the H55F down the road. Even further down the road, I think I would consider an R2.8. I know big dreams, but have to have something to look forward to.

I also should have added Land Cruiser Heaven (@FloridaFJ80) as an option as well.

There are more issues with installing an H55F than just cost... You’d lose the Orion, you would have to relocate the frame cross brace behind the tcase, source a longer front and shorter rear driveshaft. You would also need to move your ebrake to the rear axle.
I would say either source an H41 with the proper output shaft spline count or rebuild or source a new SM420.

I don’t know that LCH has experience rebuilding transmissions, especially US ones. It is not something I would trust to someone who doesn’t have extensive experience and skills in rebuilding manual transmissions.

 

[FJCowboy]

There are more issues with installing an H55F than just cost... You’d lose the Orion, you would have to relocate the frame cross brace behind the tcase, source a longer front and shorter rear driveshaft. You would also need to move your ebrake to the rear axle.
I would say either source an H41 with the proper output shaft spline count or rebuild or source a new SM420.

I don’t know that LCH has experience rebuilding transmissions, especially US ones. It is not something I would trust to someone who doesn’t have extensive experience and skills in rebuilding manual transmissions.

@Stumpalama really appreciate the insight and agree, I would prefer to have a transmission SME do the work. I didn't' realize all of those other factors would come into play. I feel like when I've read the other threads about the swap, it was "fairly" simple. Fully recognize I still have a lot to learn and I may not have fully comprehended what all is in in the swap. Outside of County Transmission or @OTRAMM are there other shops folks would recommend for an old LC? At least, I can get them to take a look and give me an estimate on a rebuild and/or sourcing an H41.

 

[Jakes40]

Swap in a SM465. I’m did a bunch of resource when I put my 465 in but can’t remember the difference in 420 to 465?? I know the 420 is harder to find than the 465. Not sure if the Orion will bolt up my guess is no!

 

[Stumpalama]

some good info here: The right 4 speed tranny for my FJ40??? SM420??

 

[Stumpalama]

The key is the 10spline output from the trans.

 

[FJCowboy]

some good info here: The right 4 speed tranny for my FJ40??? SM420??

@Stumpalama Great find and tons of good info in there. Sounds like the SM420 is the way to go and I'm already built for it, which is helpful. Now to find a replacement kit and shop to take a look. Really appreciate all the assistance.

 

[Jakes40]

The slipping out is probably caused by the shift forks being worn or bent. Fairly easy to replace. Hardest part is getting the top plate off and back on.

 

[jcj_78FJ40]

Wow, SM420 and Orion. That's some low gearing

These guys are pretty helpful.

Parts for the SM420 Transmission

Parts for the SM420 Transmission

www.novak-adapt.com

 

[FJCowboy]

The slipping out is probably caused by the shift forks being worn or bent. Fairly easy to replace. Hardest part is getting the top plate off and back on.

Wow, SM420 and Orion. That's some low gearing

These guys are pretty helpful.

Parts for the SM420 Transmission

Parts for the SM420 Transmission

www.novak-adapt.com

@Jakes40 Good to know about the shift forks.
@jcj_78FJ40 I'm starting to learn the SM420/Orion combo seems to be legit. Those are great references and I think I'm going to look get one of their refurb kits and reach out to County Transmissions and see if they can do it.

 

[FJCowboy]

Quick update for anyone following. I went to http://www.countytransmissions.com/ and really liked the crew there. They were only able to do a test drive and recommended dropping the tranny and doing a rebuild and/or swap. That would take about 2 weeks to complete the job and therefore we decided to wait for a winter project. They were really great and upfront. Basically labor would be the same to pull the tranny and rebuild it as it would be to swap in replacement. The plan is to have a rebuild kit on hand, most likely from Novak (the original came from them). Also, work with Novak to have a replacement SM320 on standby. @Jakes40 in chatting with another mechanic buddy, he mentioned something similar and felt we could at least take the shifter out and take a look versus having the shop do it. Much cheaper.
More to follow...

 

[StaleAle]

Orion's were known for slipping out of gear going downhill, are you sure the problem isn't with the Orion transfer case? I think they got the cause and a fix for it figured out a few years ago, so it might be worthwhile to do a little research on what the fix was, and whether or not your unit was refitted.

 

[FJCowboy]

Orion's were known for slipping out of gear going downhill, are you sure the problem isn't with the Orion transfer case? I think they got the cause and a fix for it figured out a few years ago, so it might be worthwhile to do a little research on what the fix was, and whether or not your unit was refitted.

Hmm...pardon my ignorance and maybe I confused the thread. Would the Orion transfer case affect the transmission if it is in 2H? This is occurring on pavement and on the trail. I can physically feel the transmission shifter popping out of gear vs something in the TC. It normally occurs from a stop, but it does pop out as well while driving if there is no torque on it. I'm hoping we can have a tech day or even a one-off tech day to have someone see it in action. I will be at Fall Crawl, so several can take a look and give opinions. Thanks for the info and definitely something to research.

 

[Stumpalama]

Hmm...pardon my ignorance and maybe I confused the thread. Would the Orion transfer case affect the transmission if it is in 2H? This is occurring on pavement and on the trail. I can physically feel the transmission shifter popping out of gear vs something in the TC. It normally occurs from a stop, but it does pop out as well while driving if there is no torque on it. I'm hoping we can have a tech day or even a one-off tech day to have someone see it in action. I will be at Fall Crawl, so several can take a look and give opinions. Thanks for the info and definitely something to research.

No. the ORION issue was specifically in the T-case. It did not affect the transmission. The ORION lever would physically move to neutral.

 

[FJCowboy]

No. the ORION issue was specifically in the T-case. It did not affect the transmission. The ORION lever would physically move to neutral.

Thanks and I haven't had any issues with the ORION to date, but good to know to be on the lookout for.