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Discussion Starter · #1 ·
I have a Wagon with an Onan L634T-A swap. I'm trying to hunt down a rear mainseal (no one in U.S. has one) or identify a potential replacement from another engine series. If anyone has experience with this engine, I would be glad to pay for an hour of their time.

Rear Mainseal: C0509020300 (C0509016900)
Rear Seal Plate Gasket: C0101077600


Wood Sleeve Font Gas Bumper
Wheel Tire Automotive parking light Sky Vehicle
 

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That engine is a Cummins 6AT 3.4 liter. That engine is unique and as far as I know doesn't share parts with other Cummins engines. First off, those number you have there are aftermarket numbers, not the Cummins part numbers. C0509016900 is probably 509-0169 or 509-0203. Here is a link to this parts manual. This could be invaluable for you. 934 0255 Onan L634T A Diesel Engine Parts manual (09 2013) : Free Download, Borrow, and Streaming : Internet Archive Looked at little more and found the crank seal is 509-0203 and the gasket is 101-0600. Parts 39 and 40 in the diagram below. Not totally sure, but that F in the serial number may mean you engine was built by Ford. There are also GM versions of this engine.
Font Schematic Parallel Engineering Auto part
 

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Discussion Starter · #5 ·
I have that manual and an original. Those are the numbers cummins and distributors currently use. None exist in the US. Tried everything on the interwebs.
 

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Just did some more searching and found a road version of that engine which is the 6AT3.4. That ESN is 53120873. That was the good news. The bad news is the parts you are seeking are listed as obsolete and no longer available. These engines are over 30 years old and I guess Cummins has declared them dead. Unless you can find a major Onan shop that may have some in stock the odds are looking grim. One possible source might be military or a marine shop. The military bought those generators so they might have parts but that's a long shot.
 

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Discussion Starter · #7 ·
Just did some more searching and found a road version of that engine which is the 6AT3.4. That ESN is 53120873. That was the good news. The bad news is the parts you are seeking are listed as obsolete and no longer available. These engines are over 30 years old and I guess Cummins has declared them dead. Unless you can find a major Onan shop that may have some in stock the odds are looking grim. One possible source might be military or a marine shop. The military bought those generators so they might have parts but that's a long shot.
Thanks. Definitely not looking so hot.
 

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What Ed said. There should be a National (or whoever actually built the seal) number stamped on the seal itself. They likely just pulled an off the shelf seal and incorporated it into their engine. If worse comes to worse, carry it down to one of the big bearing and seal stores and they should be able to match something up.
 

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Have you tried contacting Cummins to see if they have a recommendation? It is most likely that the crank seal was made specifically for them but stranger things have happened.
 

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Discussion Starter · #12 ·
Update for the geeks who are interested. I've hit every single internet spot imaginable and anyone who may still work on old Onan's. No luck. My friend is a distributor/manufacturer and has a National Seal connection. I put a caliper on it and got the numbers to see if they could match it. Supposed to get some samples back this week. Apparently when there is a "-" or other symbols on a seal it means that it was an OEM seal made specifically for that series and manufacturer. They obviously can match the spec for any seal, but they cant cross reference by the OEM seal number they originally produced and everyone else will say yer shit outta luck. Very annoying. Anyway....I didn't pull it for fear of damaging, but will try to get a handful of seal samples for next go around. Good times.
 

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If that seal has a Cummins part number they have a detailed engineered drawing of it with complete specs. You need to contact Cummins. Their toll free customer service line is 1-800-286-6467. They also offer an online chat line. If you can get a hold of one of their engineers he can pull up the original drawing. They might also give some advice as to where to get the parts you need.
 

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Discussion Starter · #14 ·
char1355...as I said before I've called Cummins numerous times....they dont have an original drawing immediately available and were not too willing to dig in the archives / microfiche...if it even exists. The dude on the phone went as far as to ask "have you tried google". Sigh. Anyway, if anyone has actually had success getting old dimensional drawings from Cummins, I'd love to know before wasting more brain cycles.
 
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