SM420 swap info

I have a sm420 with adapter and v6 bell housing sitting in the shop, I'd like to swap it into my dads stock 67 with a v6 and a T14 as his clutch is shot and I'm pulling trans anyway. Does anyone know what clutch/ pressure plate to use as well as the throw out bearing? I' guessing I'll have to redo my drive shafts, swap for a 6 spline bull gear, anything else? I'm looking for an easy swap here, Dad needs his Jeep up and running again soon. Any info would be great, IS the sm420 to old and obsolete now? It's been years since I did my T18 swap into my 3b. Thanks

 

I used LUK 01-029 clutch kit when I did mine.
Diaphragm type pressure plate.

 

I had a couple issues with my install. The bell housing on mine needed to be machined. The shift rail stuck out past the front of the case and the buick bell did not have a relief there. I had to get a couple T/O bearings until I found one that worked correctly. The one that the kit came with did not work for my application. I don't know off hand which one I used. There are charts that give dimensions. The bottom 2 bolts also need to be put in from the inside of the bell housing. You have to drill out the threads. this negates the possibility of pulling the transmission while leaving the bell in place.

The biggest issue I had was due to the thicker flywheel used on the V6. This caused the whole clutch assembly to be pushed back toward the transmission. The clutch friction disk hub was jammed all the way back and the input shaft splines were not cut far enough back to allow this. The clutch would not release.

To remedy this I cut a chamfer into the clutch friction disk hub. When I asked people about this, no one had ever heard of such a thing. Over time I have subsequently found others who had this similar issue. This solved the problem.

I have recently installed new bearings and synchro rings in mine because I had to double clutch into 4th. SM 420 new synchros and bearings | EarlyCJ5.com I really like my transmission, but some parts are not easy to find such as clutch keys/dogs or whatever you want to call them. Synchro rings seems to come in a couple different iterations that may be difficult to source. There is no provision for back up light switch and pre 53 units do not have a front seal unless you get one made from Novak or do your own engineering.

Its a great transmission for 100 bucks or less because its super old. The sm 465 is a better choice for parts availability, but is a bit heavier. The killer price is the adapter for either of these transmissions to the D18. 500 plus bucks. I saw a jeep t-18 go for 400....

 

I did experience some of the same disc splines/input shaft splines or hub face of the disc interference as mentioned above.
Took the trans out 3 times trying to figure out why the clutch wouldn't release.
The Jeep shop that sold me the clutch finally figured out what was happening and modified the disc hub or splines by cutting them down (chamfer).
They had been using LUK for years and years and hadn't had any issues.
After making all the measurements and modifying mine, they checked the other two LUK V6 clutch kits they had in stock.
Those disc hubs measured the same as mine before modification.
They modified those right away as they said LUK must have changed something to do with the disc hub.
Anyways windy, don't let that discourage you.
Well worth the effort.

 

This post reminded me of a question I have too . I have an old SM420 sitting under the bench and am planning to do the swap in a year or 2 and do the Saginaw PS swap new exhaust etc., at the same time. I figure I will have the tub off for new floors etc and that should make mounting things easier. How much longer is an SM420 - Dana18 combo than the stock T90-D18 set up ? Thanks T.J.

 

its not the combo, but the adapter from the sm420 to D18 to allow the universal from the D18 to the front axle to clear the SM420 case. Its about 4" longer which makes the driveshaft lengths change. If you look at Meisers "Rango" build on Pirate you can see what a home made set up looks like and the issues it presents. I bought the Novak adapter, bolted it on and was done. Its worth it. I am sure the AA kit works as well.

 

If you look around the net there are articles about putting the backup switch on the transmission. The last year these were made (1967) they had a backup switch installed.
I never had the disk problem when I installed the sm420 in firefighter mikes cj6.

 

If the input shaft spline root is the same diameter as the input shaft behind the splines there should not be an issue with running out of travel. The issue is the input shafts where the o.d. of the splines is close to the same as the o.d. of the shaft behind the splines. On those it can be problematic with the thicker 225 flywheel. This can happen on T-18's, SM-465's, etc. etc.
I've posted up about this issue on the old board but that may disappeared as that was several hacks ago.

 

Yea, I wasn't at the shop the day they pulled mine back out of my Jeep.
And I was busy with work that day and couldn't drive by.
I just recall them saying they cut down the hub face and/or chamfered the spline area on the flywheel side of the disc.
They mocked it all up in the shop and took measurements.

 

What I was looking for was how you adjusted for the length change and where things ended up to compensate for the extra length. Did you leave the engine in its original spot or shift it around I assume that the rear mount must get moved back and the drive shafts replaced/modified etc. Thanks T.J.

 

Only picture I took of them side by side.
Offy V6/T90 adapter/T90/D18/Warn overdrive.
vs
SM420 ad Novak adapter.
You can also see the factory cross member under the T90/D18 and where it will end up
due to the holes shown in the Novak adapter.
Yes, the drive lines will have to be lengthened/shortened accordingly.
On my 2A, yes the V6 remained in the mounts; the stok cross member was moved farther back.

 

I was wondering if the engine got moved forward a little bit , I'm considering replacing my firewall with the one off of the parts Jeep tub as mine was totally butchered when the engine was swapped it was bashed for clearance sections torched out and patches pop riveted all over. It was done by a 15 year old who didn't have the experience yet to do better. But I want to make it right since I have the equipment and the skills and mostly I don't want my friends to think I did it that way.

 

Thanks JP a picture can be worth a thousand words did you have to modify the shifter ?

 

Yes, the shifter needed to be modified. I cut mine off, tacked it where i wanted it and finish welded it.

 

I heated it to make the bend I wanted; then I shortened it and rethreaded the cane for the knob.. remember I'm a CJ2A...maybe more cane to dash clearance in a CJ5?

 

When i did my swap back in 1999, i used a Center force package. the P.P. was #cf 361662
the disc was #383271, and bearing #tim 1377c . The total amount at that time shipped was
$ 250.00. I also had to grind the side of my case to clear the front u-joint and fab a new bracket
for my single shift lever. I used a A.A. adapter. I drilled out the bottom holes on the 420 and put a
stud in the bell housing, instead of bolting from the back side into the transmission.I also heated
my shift lever and bent it to where i wanted it. I also put in new drive shafts. I had no clutch issues.

 

Did Chevy/GMC always have a drivers side drop on the transfercase and front axel? Was wondering if you could maybe just put in a whole GM V6/tranny/tc and maybe a matching axle with front and rear geared the same?

 

wow that package is Long

 

How my shafts ended up length wise after the modification process and 5 new u-joints.
V6 in CJ2A
$294 total locally.