When I'm driving down the highway and I hit high RPMs the clutch starts to slip. Mostly its in 4th gear goining up a hill or if I pull out and take off kind of fast. The SM420 that is in there is one of the earlyer ones that I've heard don't have a seal in the front, is that true? It seems to be leaking and if it leaks on the clutch then that is probably why it is sliping right? Is there anything I can do? Seems like the only thing to do is look for another SM420 and swap it out...joy more $$$ to spend(already went through one useless sm420:rolleyes: ). WTOR did the work and said that they couldn't make a seal for the SM420 so what can I do? Its not that big of a deal, unless you pull out and cant get moving with a truck on your arse:eek:
Thanks :flipoff2:

Joseph A.

If you have the proper front bearing retainer, it has a hole that allows the gear lube to drip out before it hits the clutch disk. At least that is the way it is supposed to work with the early model w/o the seal.

The easy thing to do to find out would be to pull the inspection cover and see if there is any gear lube on the disk or whether it is worn out. Either way, you need to replace it.

Also be sure you haven't overfilled the tranny. My similar (no seal)setup doesn't seep fluids from the tranny.

I did pick up another tranny that has the seal (dried out) in the bearing retainer. Does anyone know if this can be retro'd onto older input shafts?

I'm having the exact same problem! Doesn't happen all the time though. If I replace the clutch, is it just going to keep happening because of something inherent in the tranny? I would think there are enough SM420's out there that someone's got a good fix for this. I'd appreciate an help with the matter as well.

could it be the rear main seal on the motor, blowing oil on the flywheel?

I've also got an early sm420 without the seal, and it leaks a little bit on very steep downhills but I haven't had a problem with a slipping clutch, even though I've noticed some oil around the clutch housing and pressure plate. If you haven't replaced your pressure plate recently, I would place that on the top of the list.

BTW - You can't just replace the bearing retainer from a later model sm420. The input shafts are different. The earlier models have an oil slinger and reverse rotation threads on the shaft that help to draw the oil back into the tranny. The later models are machined for the oil seal.

Originally posted by adamto
I'm having the exact same problem! Doesn't happen all the time though. If I replace the clutch, is it just going to keep happening because of something inherent in the tranny? I would think there are enough SM420's out there that someone's got a good fix for this. I'd appreciate an help with the matter as well.

Adam,
I was concerned about the same problem back in January during my 420 rebuild. Here is a link to the thread:
http://www.pirate4x4.com/forum/showthread.php?s=&threadid=27871&highlight=sm420
My 420 is on the back burner for now. I want a AA rockbox
:eek:
Call Greg at Tourist Auto in SLC 1801-364-5743 or better yet ask for Greg's dad at the shop. He will know.
I was told that a newer model input shaft and retainer with the seal would solve the problem. That would be an easy and not so expensive change. The old style cannot be modified, I looked into machining mine and it would not work.



Or here is a link to a guy that knows everything.......

:smokin: http://www.Jameshenrycrusieropinions.com;)

Originally posted by bennett


Or here is a link to a guy that knows everything.......

:smokin: http://www.Jameshenrycrusieropinions.com;)

That is toooooooooooooo funny!

I just drained the transmission and shot the clutch with brake cleaner and de-greaser. Let the clutch dry out and filled the trany with about half as much fluid. Drove it around, started off in 3rd, and did some racing around in it and had no slippage. I'll be gone this weekend so I parked it in a clean spot. I'll see if its leaking anymore sunday or monday.
Thanks for the help... go buy yourselves some :beer:
:flipoff2:

Joseph A.

Just got back...its been 2 days and only a drop of tranny fluid on the ground.
So if you have a early SM420 without the front seal and its leaking, then drain that SOB and feel it up with half as much...
Also solves clutch slippage problem :flipoff2:
Thanks for the help...

Joseph A.