SM 420 vs. SM 465

Which would you chose?

Is the 465 quieter?

Pros cons?

I'm on the fence, going to buy one or the outher.

 

Thanks for moving this wasnt sure where to put it.

I have read all the usual stuff on them, novak ect.
And know the pros and con of the install. And thier spec's.

Was hoping for some real life opinions on likes,dislikes ect.

 

I put in the SM420 and it is fantastic. I would recommend it because it's (slightly) smaller and lighter (but still big and heavy).

It's so much stronger than needed I don't think it matters that it's old and hard to find parts for.

Just my .02.

 

I would go with the SM 465, becuase it is a newer design, easirer to get parts for, adapter is shorter and cleaner looking, makes for a shorter package than SM 420. I mainly do not like that long adapter for the SM 420 which puts the T-case away from the transmission. With the SM 465 it looks like they belong together.

 

:iagree: woulda been a tossup for me though before Novak came out with their 1" adapter, If they come out with the same setup for the 420 it's gonna be a tossup again...for me anyway.YMMV

 

The sm420 transmission itself is smaller 135lbs versus 175lbs with the exception of the hump on the passenger side, which is why the adapter is longer, its also shorter but this is negated by the adapter length. The sm420 has a better 1st gear, the reverse on the 420 is much harder and noisier to shift into than the sm465, the sm420 is easier to disassemble do to the design of the reverse gear and the absence of a reverse shift fork. The parts issue being difficult to find is mainly a local issue, around here the sm420's can be had almost anywhere for around $75-$100. I have bought 5 of them for $75 and got 1 for parts for $10. They are noisier than the sm465 but there not as loud as the dana 18 transfercase. Getting parts to me is almost a moot point as there damn near impossible to tear up in a jeep with a 6 cylinder or small v8. All of the general rebuild parts are available though, its the mainshaft and gears that are not available from the dealers. They were made for more than 30 years so there are lots of them out there, if you use one just find one for spare parts and forget it. The sm465 has to be completely disassembled to adapt to the dana 18 and this is time consuming and not easy or doable for everyone, the sm420 can be adapted in about an hours time and does not require disassembly of the transmission.
Another thing is the Buick bellhousing and sm465 front bearing retainer must be modified to work, the sm420 needs no modification.

 

I love my SM420 and wouldn’t trade it now that I’ve already got it adapted in, but if I were to do it over I’d probably go with the SM465 just for the parts availability. It’s been a long time since 420’s were used and no one is making new parts for them.

 

I got the 465 because, well, I found one for $50, got the right bellhousing for free, and I've had a 4.3L just sittin' around. I got lucky (I think) on my finds, and that's what I'm runnin'. If money wasn't an issue (as it always IS), I'd probably use the 420, just because of gearing.

 

Oh how I love my SM465. I can drive the trails in 2nd or 3rd gear. (In low of course.)When I need to crawl over rocks I just put it in 1st. I've also found I don't used any brakes when trying to go up steep hills, if I get stuck in a hard spot. With the low gearing of the transmission it just slowly rolls backwards when I put it in reverse. This was the best upgrade I made. :smash: :driving:

 

I have the sm465 behind a 4.3 GM. I've only been test driving it for about a week. It's not that noisy, but it is certainly noticable. I thought the NV3550 in the TJ was an unrefined transmission, until I drove the SM465. Don't be in a hurry to shift.

Paul

 

I have a SM465 and love it. I picked mine up for $50 and parts are pretty easy to come by, I had to replace a main shaft on mine and a local tranny shop had one. SM420's in these parts are getting pretty hard to come by. I agree the 465 is a bit large but with the Novak kit it is manageable. The crawl ratio with my 4:88's works out to around 78:1, the SM420 is around 84:1, not sure if that is a noticeable difference.
For me this was not a cheap conversion but well worth the money as I mainly drive on very rocky trails. Shifting between 1st and rev. is very easy with the 465 when you are in a tight spot.

 

Re the shift speed, I expect the biggest part of the slowness is due to the weight of the gears. Even the Borg-Warner 3-speeds are slow shifters compared to passenger car transmissions, and the 4-speeds are worse.

Rolling downhill can blow up your clutch disk - don't let your 4-speed in 1st-low or R-low roll on its own with the clutch in ... neutral or engine braking only. There's so much reduction, you can spin the facing right off the disk.

 

Wow!

I appreciate the advice

So it would seem the 465 is better at shifting from second to reverse.

I am using my 225 and buick bellhousing.
So the 420 would be easier to swap.

So is the 465 quieter and smoother reverse shifting ,enough to go to extra trouble or not.

I can get a rebuilt 465 with warrenty all day here.
Or I can get the 420 and adaptor from Herm, but have to add shipping.
And I cant figure out where to ship it to, that would drop ship it except my wifes work and thats out for sure

Thinking...

 

Love these posts. I've decided to go with the 465 since I've got one...

But does anybody have more info on adapting the 465 to the F or L head motors? I've seen mention in the 41-71 CJ rebuilders book that Advance Adapters had parts, but nowhere on their site could I find it. I know their are a few on this site... Anybody?

 

AA is better on the phone.
Personally I dont know.
But it should be out there.

 

Nobody to my knowledge makes an adpater for the L/F head to a SM465 or SM420.
The sm465 needs to be disassembled to adapt to the dana 18 even if it has been rebuilt. The mainshaft has to be changed out to use the 1" adapter, which requires taking the entire thing back apart. The sm420/465 thing is a cost thing in my opinion, get what runs the cheapest and the easiest for you. They will both require driveshaft and crossmember work, the adapters are roughly the same cost, so to me it boils down to what you can find and get the cheapest and easiest.
When it comes to truck 4 speeds none of them shift like a modern car transmission, but then again the Jeeps don't drive like modern Jeeps or anything else so at that point it not really a big deal at least not in my experience.

 

You're right Mike, and that's what I was expecting. But just once, with the 4.3 and dual exhaust, I'd like to bang that thing through the gears. :twisted: Just not going to happen. Sprung over and 35's to boot. It vibrates, it creaks, and it's old, but I like it.