Sorry, I guess I had the check box marked to hide from public view. Thanks again.

That makes sense. I have 2 600 cases that have sleeve style bearings, and one that has 2 sets of needle bearings. (all have the rollers on top) I wanted to remove them to use in another case, replacing the sleeve bearings, and drill and tap for a grease zerk. Thanks again guys!

Scott,

   Interesting questions... 

   Question 1:  According to the Peerless 600 Series Parts Lists, your 639 has a left axle housing that's 2-11/16" long and a right housing that's 6-27/32" long.  Your 612A has the same left housing but the Parts List doesn't show a Peerless right housing (?).  The right housing may have been supplied by the OEM.  If you have "all different length" housings, they've been changed at some point.
Axles
Left Side                                                            Right Side
Length – Part Number                                    Length – Part Number
  8-37/64” (8.578” / 21.8 cm) – 774368       10-15/32” (10.468” / 26.6 cm) – 774286
  8-3/4” (8.75” / 22.2 cm) – 774352            14-27/32” (14.843” / 37.7 cm) – 774079
  9-15/64” (9.234” / 23.5 cm) – 774221       15-1/4” (15.250” / 38.7 cm) – 774137
  9-13/16” (9.812 / 24.9 cm) – 774304        15-21/64” (15.328” / 38.9 cm) – 774241
  9-63/64” (9.984” / 25.4 cm) – 774298       16-1/8” (16.125” / 41.0 cm) – 774305
10-9/32” (10.281” / 26.1 cm) – 774138       16-13/16” (16.812” / 42.7 cm) – 774285
10-27/32” (10.843” / 27.5 cm) – 774410      17-1/8” (17.125” / 43.5 cm) – 774411
10-55/64” (10.859” / 27.6 cm) – 774240      17-13/16” (17.812” / 45.2 cm) – 774367
12-3/16” (12.187” / 31.0 cm) – 774078        17-55/64” (17.859” / 45.4 cm) – 774220
12-3/8” (12.375” / 31.4 cm) – 774284         18-39/64” (18.609” / 47.3 cm) – 774299
19-1/16” (19.062” / 48.4 cm) – 774287

   The above list shows the 600 Series axles that use the most popular style of axles, the ones that have a straight keyway and a snap ring to hold the wheel on.  There are other styles and lengths of axles available for the 600s, a total of 37 lefts and 34 rights.  Axle lengths vary from 6-11/16” to 19-1/16” on the left and from 13-1/16” to 19” on the right.  Axle-end designs came in keyed, pinned, snap-ringed, internally threaded, “Double-D” flattened (the infamous MTD), or a combination of these.

   Your 639 uses left axle #774221 and right axle #774220.  Your 612A uses axles not on this list, as the 612A axles use a woodruff key instead of a straight key — your 612A left axle is 7.0” long #774133 and the right axle is 17-11/16” long #774134.

   For proper support, you may need to use frame-mounted ag-style bearings inside your wheels to keep the axles from bending.  I'm not sure extending the supports would be a good idea.  And...if your spacers or wheels are just outside the axle housing, ALWAYS use a thrust washer between any spacer or wheel and the housing to prevent the housing from being gouged.

   The answer to Question 2 is "get the gaskets" since the gasket thickness is part of the clearance engineered into the case dimensions to allow for proper internal gear, shaft and bearing clearance.  It's okay to use a thin layer of RTV to supplement the gaskets, but never eliminate the gaskets.

   Question 3:  The easiest way to lock the differential is to replace your 600 axles with MST axles and install an MST Diffy-Lock Gearset Upgrade 5 (locking spider gears), especially since ALL the axles listed above are obsolete.  The inner ends on your 600 axles have the "Double-D" flats; the MST axles are fine-splined.  Upgrade 5 will replace the original spiders in your 600s. 

   Question 4 (Thread 2):  The 600s use a ball bearing supporting the top of the input shaft, inside the housing (like an 820 transaxle), with a bronze bushing below the ball bearing.  The grease zerk is a good-idea modification.  Peerless input-shaft bushing and bearing Part Numbers: Bronze - 780061; Ball - 780093 (all except plain 612, including 612A), 780092 (plain 612).  Bearings and bushings are still available.  Your "steel bushings" are not original. Are these bushings or needle bearings?

   Closely inspect all remaining bearings and bushings when prepping a transaxle or transmission.  Replace any worn or questionable items. 

   Final Note:  As more of the 600's parts become obsolete due to its age, you might want to plan on replacing your transaxle at some point with an MST 200.  It's not only more current and more popular, but its inline-shift pattern also makes it easier to shift and it's available with up to six speeds.

Thank you so much! I can't wait to see it! Thank you for taking the time to do this, as I know it might help other people besides myself. One of the cases I have must have been "race prepped" to some degree as it has a bronze bushing at the input shaft and a grease zerk installed to the input shaft housing. I noted that the other 2 cases have steel input bushings. Is there a recommended list of bushing and bearings that should be replaced when prepping them? Thank you once again.

First, is there a master list of all the different axle lengths and support tubes that are available? Reason being is I have 3 of the 600 series and all 3 have different length axles and tubes. (2 are 600-639, and the other is 600-612A) Also if I went with a longer axle, would I be able to just use a pipe with 3/4" inside dia. as a sleeve to reinforce? I read on here about it, but it did not go into much detail, like do you need to add thrust washers or anything where it may contact the end of the tube? I was worried about the axle bending where it leaves the support tube.

Second, can you just use RTV to seal the case? Or should I get the gaskets?

And third, locking the diff. Is there any trick besides using a piece of 3/4" drill rod. I don't have access to a machine shop, so adding a keyway is not an option for me. I was almost thinking about adding a piece of square tube between them, or welding the spider gears and then grinding them down like the locker kits I have seen for the other transaxles. I have not measured to see how much room I have for extra stuff in there either. I figure I would ask before trying to re-invent the wheel.

What are you guys using for the exhaust header on these engines? The stock header pipe is about 40 bucks... A bit much just to chop up.

Thanks everyone for the help, I did not know if the coils where the same, and I know some had a resistor, but I had no idea they where THAT universal. I believe it does has a condenser, but I will have to double check. Thanks again.

It looks like an automotive type coil, but I did not know which one it would cross to. I was hoping to just go to autozone or napa and pick up something cheap, or do the ebay thing and wait. Why would an auto coil not be good if I could find one? The Kohler coil is not as cheap, and I don't even know if the engine will run, so I did not want to invest much money into it only to find it's junk.

Thank you so much for your quick response!