SM420 or clutch issue?

I just put an SM420 into my 1969 CJ5 with 225 v6 a few days ago. While everything was out, I put in a new clutch set. Got the tranny and dana 18 twin stick all together using an advance adapter spud shaft kit. Everything went really smoothly. Got the driveshafts made and stuck them in and I drove the it around town for two days and everything was working great. Today a few friends and myself took our jeeps out riding in the snow, and still everything was working great. Found a big mud hole and tested it out for a while with no problems. On the way back to the house, the transmission started not wanting to gear down i.e. it was grinding until I came to a complete stop, however it did fine gearing up while driving. Got to the house and played around with it in the garage for a while and realized the jeep won't roll backwards when the clutch is pushed in... For instance, I can put it into reverse with relative ease and let out the clutch and drive backward, but when I push the clutch back in, it comes to an abrupt stop almost like you slam on the brakes. With the tranny out of gear, it rolls fine, however when I put it in any gear R or 1-4, my buddy couldn't even push the jeep back while I have the clutch pushed in... any one have any ideas?? Ive tried adjusting the clutch cable tension, good fluid in tranny/tc... I'm at a loss any one have any ideas??

 

Did you notice any change in the feel of the clutch. Are you running a bell-housing dust cover? May have gotten sandy mud in clutch.

 

Thanks for the responses guys. I will check all the bolts this evening after church. The mud I was in was pretty gritty, and it was about 28 here so it's possible I could. E panicking over a little grime in the clutch. I will give it a good bath and check the bolts and see if anything changes. Thanks again.

 

Did you check E brake , could be stuck

 

Hey there, I know your pain! I just put my drive line back together old clutch and all, now I have similiar issues like you!!! i cant really tell until I break drive line down again...Worried shread the input gear or.... I'll see. Anyways ucdaniel wanted to ask about your sm420 swap, as I was looking at the used sm420 mated to a 20 that I have hanging around the garage, maybe its time to swap this into my 5!! You used stock flywheel for your sm420? BOP bellhousing pre1970? 10.5 clutch from what year? How about clutch linkage? How u deal with tranns mount? Oh ya how much shorten or lengthening on drive shafts??? Hope this site can help with your issues, I wish I had any suggestions for you! It will be interesting to know what the problem was and the fix.
Thanks J

 

No e-brake or that would be a good idea haha. The sm420 in my jeep has been the best mod I have done so far! I used the stock flywheel, same factory bell housing (1969), clutch kit from auto zone, and as far as the clutch linkage I just had to move the bracket that holds the pedal end of the cable forward about 2 inches on the frame rail. Drive shafts with the advance adapters spud shaft kit ended up moving my drive shafts 2.77" either way (front longer/back shorter). I did have a T90J out of a jeep truck in it before the sm420, but still retained the factory driveshafts. The only reason they changed was because of the sm420 being slightly longer than the T90 and the adapter kit at 4". I lost like 2" and some change in the conversion due to the factory spacer they used on the T86. We just milled it out to take the T90, but I didn't need the spacer with the 420. Good luck with the swap, feel free to holler at me with any questions and Ill do my best to help you out!

 

Thanks for info D, this site is awesome I'm sure one of the members will have insight to your issues!
Later J

 

It sounds like the linkage might just be slightly out of adjustment. Try adjusting it so when the pedal is depressed it pulls the fork just a bit further and drive it again.

 

If you are using the stock throw out bearing and leaver, the thing to worry about is the installation of the arn to the bearing. there is a spring that will get hooked over the lip on the bearing instead of being in the slot of the bearing. I also had issue with the pivot point on the leaver. It had slipped out of the retaining spring. I do not have pictures, but the service manual has a warning in it for the bearing interface. I was able to rebend the spring that holds the pivot point and make that correction.

 

Well, I ended up washing out the flywheel/clutch/bellhousing and didn't have any change. Adjusted the clutch linkage as much either way as possible, still no dice. Bolts were all still tight all around. Thought it may be the new clutch itself, so with a tear in my eye I took up the floor and took the driveshafts loose and dropped the tranny/tc/bellhousing and couldn't find any dirt or signs of wear anywhere it shouldn't be. Decided to put in the old clutch and throw out bearing, put everything back together and still the same problem... I am at a complete loss?? What in the world could be going on with this thing!?!?

 

I still don't think you're getting enough clutch fork travel. Did you inadvertently change the geometry of any of the linkage during the swap?

 

Is it hard to roll both forward and backward or just backward? If just one direction that implies a gear or shaft moving and binding. Maybe the collar on the spud shaft has slipped allowing the mainshaft if the transmission or the input to the transfer case moving and binding?


Sent from my iPhone

 

Clutch linkage would be believable for me IF it would not have shifted/downshifted perfectly for two days of driving after the install. However, I tightened the clutch cable to the point that the throwout bearing was riding on the clutch fingers all the time, and still no change. I can definitely feel a "break-over" in the clutch when I press it, just like I had with my T90. So in short, I think the throwout bearing is pressing the fingers as far as possible... As for the gear/shaft being in a bind, I think it is not in the transmission/tc because when I put the tranny in neutral, the jeep will roll free in either direction with/without the clutch pushed in. And on the flip side, it will roll free with the TC in neutral... With the clutch in, and in 1st gear lets say; I can push really hard on the jeep and rock it forward and backward, the only difference in the two is that when rolling a few inches forward, I can hear maybe the friction plate rubbing against the flywheel like its not completely free. But if that is the case, wouldn't the jeep try to roll forward on its own if the clutch friction plate was still engaging the flywheel??

 

Did you take the top off of the trans when you had it torn down? It is a pretty simple trans to work on and any thing out of place would be very apparent with the top open.

My 420 gave me fits when I got home from an outing once. The trans was acting a little strangely as I got close to home. When I pulled into the driveway, it seemed to lock up. Tear down revealed that the second gear synchronizing ring had come out of the first gear. It is held in with a snap ring that some how came loose and got eaten up(the snap ring is virtually impossible to source, luckily I was able to cut one out from a sheet of spring steel on a water jet at work). I had run over 350 miles and had been through some pretty rough terrain 50 miles from civilization that weekend! The moral of the story is that the 420 is one very tough hombre that won't let you down.

If it does turn out to be a trans problem and you need info, manual scans are available here: http://www.kinzers.com/don/landcruiser/transmissions/

 

I found out last night that the center metal on the friction plate where the input shaft splines go through was riding against the input shaft collar and was slowly filing down the collar length. I figured this could be causing the lockup in drivetrain, but after I dropped it all and lathed off about a 1/4", turns out that was just the sound I could here when rolling the jeep forward, clutch isn't dragging at all! After that I pulled the shift tower off and drained all the fluid to look for any problems in the 420. After about a half hour I find out it's only binding in 1st and R, not 234 now!? Can't turn anything by hand when the clutch is pushed in, but it seems to roll a lot more easily forward than backward. Heatseeker, thanks for that link, those are great cross section pics. I agree that it's an awesome transmission well worth the time and energy to get it fixed back up. I'm gonna take a closer look into the tranny tonight and see if I can figure something out.

 

Well, in case anyone else has similar problems, after yet another tear down, I finally figured out there was some kind of bind in the countershaft in the transmission... Luckily my brother in law had another 420 in his barn. I was able to spend All day today replacing it for the torn up transmission. Got it in and everything is working great again. Thanks to everyone for all of the suggestions!

 

I'm glad to hear that you got it worked out.

Keep the broken 420 for parts! Parts for them are getting harder and harder to find.