Balance shaft eliminator redesigned...

[jltcat]

Went to install a balance shaft removal kit for a 2G DSM. Upon installing in the front cover/oil pump it became evident that the engineering design was not sound. The lateral thrust on the oil pump driven gear will cause premature wear on the aluminum cover. Since oil pump clearences are measured +/- .001" or so clearence between the gears will very quickly go out of spec as the cover bearing surface wears.

This is what we came up with for a solution...(see attachment file)

This design will eliminate the twisting motion on the driven shaft by retaining the large rear bearing to absorb the lateral load on the gear. We realize there may be some advantage to blocking the oil hole in the rear bearing area when you intall the (eliminator kit); but any gains in oil supply will be quickly lost when the bearing surface on the front cover go out of round.

This shaft is fully balanced, and as a result there is no internal harmonics setup by the balance shaft so a very tight tolerance is possible thereby allowing for minimal oil loss from the large bearing, while at the same time retaining the tolerances in the oil pump.

 

[awd4bangr]

Nice work but various people have been doing the lathed balance shaft for quite some time.

 

[jltcat]

I never said I was the first to think of it I just wanted to display/explain it so others who havent thought of this would take it into consideration.

 

[Beemer]

You are correct on the thrust part, but the 4G61 didn't use balance shafts, and would run past 100,000 miles on the stub shaft from mitsu. Every single one of the "balance shaft eliminator kits" uses the 4G61 stub shaft. Some folks cut a groove on a lathe to ensure oil gets to the bearing surface full time at high rpm like the Buscher kit, but unless you are winding the piss out of the motor all the time, the stock 4g61 stub shaft works ok.
dave

 

[GalantVR41062]

The rear balance shaft (oil pump one) is fed down the middle of the balance shaft itself. So what I did was cut the shaft at the pump cover, tap the hole with a 7Mx1.25 tap and put a bolt and lock washer in there. My motor ran for 5500 miles with no problems that I know of, I still need to take apart the oil pump and make sure though, befor it goes into the built short block. So is it just the stub shaft that has proven wear and tear, and not a cut stock unit? The cut down shaft looks nice though, are you planning on selling such a unit or did you do this just for you?

~John