Intermediate shaft backlash problem

[David Goodman]

During my enging rebuild, I noticed that the intermediate shaft gear was worn so I replaced it. It was a "0" (identifying number) gear and I replaced it with a "0" gear. Upon reassembly, I measured the backlash at about .07 mm. the upper limit in the PP rebuild book and the factory manual .049 mm. The crank gear does not look worn at all, and it seems hard to believe that the aluminum I-shaft gear could cause wear on the steel crank gear. Any opinions on this ? I am really having a hard time deciding what to do here. I can replace the "0" crank gear with a new "0" gear but I am afraid I will still have the same backlash problem (FYI the gear is $275). I also noticed that in the factory manual certain combinations of gears are permissable for my "0" block (Sec. 38EN page E93). One possible combination is a "0" crankshaft gear and a "1" intermediate shaft gear. Based on page 93a, it appears that the "1" I-shaft gear is .05 mm larger than the "0" I-shaft gear. Is this an acceptable method of reducing my backlash ? Any help on this would be greatly appreciated.
Thanks,
Dave

[john walker's workshop]

two hundredths of a mm is not a whole lot. good luck finding a new "1" aluminum gear these days. not much you can do but run it.

[David Goodman]

Thanks John. Does this mean that I shouldn't bother replacing the crank gear ?
Dave

[john walker's workshop]

as you figured, it really doesn't wear much, running against the aluminum gear. the aluminum gear sure does. i guess it's a try it and see thing, if you want to spend the dough. once everything is torqued up, the clearance may decrease a bit anyway. they're just laying in there loose now. the shop manual shows a measurement technique for the aluminum gear, but not the crank gear.

[jimz61]

Are you sure that your I-shaft gear is supposed to be a "0" gear? Check the case for the number to be sure you didn't already have a "0" gear in a "1" case.

[Wayne 962]

It's tough to accurately measure this, you're .07 may be off...

-Wayne

[rcwaldo]

I ran into this exact situation last year while rebuilding a 2.7L. I was about .002 thou out of spec as per a dial indicator and human eyesight. I ended up runnnin' it with no issues of noise.

Like John said, once the cases are botled together, that lash will more than likely decrease. Also, with heat, that alu gear will expand some and help you out even more!

Now glue that thing together already!!!

Chris

[David Goodman]

Thanks guys for the help.

Jimz61 - It's definately a "0" case. The book says I can have a "0" or a "1" I-shaft gear with a "0" case and a "0" crank gear.

Wayne - I checked the measurement several times with the same result.

rcwaldo - Thanks for the encouragement. I've got so much $$ into this thing that I want it to be perfect. At some point (soon because I'm running the One Lap of America again this year) I've got to bolt this thing back together and move on.

So this is what I am going to do. Tomorrow I have another new I-shaft gear arriving from a respected engine builder in FL who has them custom made for him sized between a "0" and a "1". It's going in the block tomorrow, I'll let you know how it goes,
Dave

[Wayne 962]

I wouldn't really worry about it...

-Wayne

[snowman]

THis this is NOT critical in any sense of the word. The only thing that can go wrong is, NOTHING. There are specs that are important, and specs because you got to have specs, this is one of them. You may get some scatter in the timing due to the valve train jittering a little, but I don't think you will be able to measure it let alone feel it. As long as you are constantly pulling, ie accellerating you should not know the difference. If you let off it and then get back on it there may be some kind of a miniscule hickup, but I do not think that at the difference you are talking about there will be anyone who could tell the difference.