Topic: proper flywheel / clutch set up for 20R to L52

[jmac80]

Hello folks,  I'm doing some preplanning for a next Spring project (if I can postpone it that long).  I'm getting confused looking at Marlin website and other aftermarket parts sites.

I have a 20R w/ L52 in it.  The tranny input shaft seal or housing gasket has started to leak, and I plan to change clutch and probably the flywheel when I do this.....clutch grabs sometimes and has for a couple of years now.  I think there are hot spots in the flywheel.....I also think it may not be balanced well and causing some vibration over 3k RPMs......anyhow, when I look at parts Marlin's flywheel doesn't show compatibility with the 20R but many aftermarket part stores do show flywheels which are 20R and 22R compatible, does Marlin's work on a 20R?  Also, seeing similar type info for clutch, Marlin offers a 79-80 and then an 81-88 clutch.

Which clutch and flywheel do I need....I'm thinking the 79-81 for both?......do I just need to by a flywheel elsewhere and clutch from Marlin; if so, what brand should I go with?

I plan to buy the 1200 lb clutch.  It's my DD w/ 31's on it.....it gets a little trail abuse from time to time but nothing too crazy....there is no reason to go with the 1600 lb, right?

Thanks in advance for your expert opinions....anybody in the Bay area with a used tranny jack for sale, I'm in the market.

[Gnarly4X]

Thanks in advance for your expert opinions....

Hey jmac80,

I believe the clutch disc for a 1980 20R engine and the 22s are the same.

Marlin makes and sells good stuff, a good choice.  I would NOT go with a 1600 lbs pressure plate.  The guys I know who have installed the high clamp pressure plates have had issues with blowing out the clutch slave cylinder.  I wheeled the heck out of my 22R 1985 truck for years with a stock style (1200 lbs) LUK clutch kit and never had a problem with the clutch slipping, including sand duning in Glamis and cross-country Mexico across miles and miles of big sand dunes and deep sand beaches.

I’m more frugal and on a limited budget, so I’d buy an Aisin, Beck Arnley, M-PACT or LUK clutch kit.  I like the quality and price of the M-PACT clutch disc I bought for my recent rebuild.

If the flywheel has heat cracks, you might consider replacing it.  A LUK flywheel is $35 or $40. You can have the flywheel machined.  My flywheel had some heat spots, so I just took some 320 grit emery cloth and flat block and sanded it to get the surface cleaned up.  Either way you could have the flywheel and the pressure plate balanced as a unit.  Any good machine will do this for you.

Edit:  On the input shaft seal, I'd ONLY install a Toyota seal (see my thread on this).  I used Permatex Thread Sealer on the bolts, and Ultra Gray on the gasket and seal housing.

Let us know what you decide.

That’s just my *non-expert* opinion – it may be worthless.

Gnarls.

[jmac80 [OP]]

Edit:  On the input shaft seal, I'd ONLY install a Toyota seal (see my thread on this).  I used Permatex Thread Sealer on the bolts, and Ultra Gray on the gasket and seal housing.

I had just read this thread immediately before posting my questions.  Thanks for input Gnarls.  Always good advice from your end.

So are the flywheels the same then?  If the clutch packs are the same then the flywheels should be too, right?..otherwise the bolt holes on the pressure plate wouldn't line up with the flywheel right?

And for the balancing thing, you just put the pressure plate on the flywheel without disc, get balanced, note orientation, dissemble, put pilot bearing in flywheel, and then install with disc on truck this time?.....obviously, you can't balance with disc loose in between the two.

....I've done a few clutches (like 3) in my life and it's been over 7 years so bare with me please.  The flywheels were always good so just did bearings and clutch only, never pulled a flywheel off.

[Gnarly4X]

I had just read this thread immediately before posting my questions.  Thanks for input Gnarls.  Always good advice from your end.

So are the flywheels the same then?  If the clutch packs are the same then the flywheels should be too, right?..otherwise the bolt holes on the pressure plate wouldn't line up with the flywheel right?

And for the balancing thing, you just put the pressure plate on the flywheel without disc, get balanced, note orientation, dissemble, put pilot bearing in flywheel, and then install with disc on truck this time?.....obviously, you can't balance with disc loose in between the two.

....I've done a few clutches (like 3) in my life and it's been over 7 years so bare with me please.  The flywheels were always good so just did bearings and clutch only, never pulled a flywheel off.

My machine shop balanced the flywheel with the pressure plate, no clutch disc.

The pilot bearing goes into the end of the crankshaft.  Make sure to test fit the new pilot bearing on the tip of the input shaft.  It should slide over the tip of the shaft easily.  Properly torquing down the flywheel bolts is always a challenge if you don't have an air impact or electric impact tool.  Then aligning the clutch disc between the flywheel and the pressure plate is also a challenge.. at least for me when I do it. Even with the plastic alignment tool supplied with the kit, getting the disc aligned perfectly is a trick. Of course if you don't get aligned, when you go to install the tranny, the tip of the input shaft will not slip into the pilot bearing and then you have re-align the clutch disc.

Gnarls.

[jmac80 [OP]]

The pilot bearing goes into the end of the crankshaft. 

  thanks for keeping me straight.

I can remember the struggle with the plastic key/alignment and getting everything back together with a W56....these 4x4 transmissions are just awkward with the x-case hanging off the side   I had remembered the check the pilot inner diameter with the shaft before install rule, but always to good remind everyone.  I'll probably post some pics of the flywheel for some input on possibility of reuse....obviously cracks are a no go but I don't really know what a "hot spot" looks like and what would be acceptable for reinstall.

....all for now, I'll bring thread back alive when I get to working on it and also finish a really old one about the over 3k vibration I've had for forever now.