Let me start the post by saying I spent some hours trying to locate an answer to this by doing searches on "layshaft", "countershaft" and "intermediate shaft". Lots of hits, but nothing I could find on my particular question. I did find a thread describing *no backlash* (not the problem here).
I'm into another engine rebuild .... One area I've never found to be of a lot of concern is that of the crank gear to intermidiate gear play. I've done the measurements before -- I have the spec books -- but can't recall all the outcomes, and can't recall ever being concerned enough about what I measured so that I bought a new gear or found a reason to change anything... Just put the intermediate shaft/gear back as it was.
On this rebuild, I have not proceeded as quickly as in the past due to some issues with the nature of this particular engine, and have spent more time than ususal researching some things. ( Anyone ever been into a '79 Factory Upgrade 3.1 liter engine, or ever seen one, for that matter?)
Anyway, the '78 -'79 spec book gives backlash numbers in the range of 0.016 mm to 0.049 mm. That's only 0.0006" to 0.0019". My measurements show 0.12 mm of backlash. Almost 10 times over the minimum number. This is about an 80K mile engine. Everything in the bottom end looks to be in reasonably good shape. The crank and rod bearings and journals show very little wear. The intermediate gear teeth surfaces don't *look* to have any abormal wear. The case is a "0", the layshaft gear is a "0", and I seem to find a "0" lightly etched on the crank gear. The backlash numbers, BTW, seem to be installation numbers, and not wear limit numbers.
I have several used countershaft assemblies lying around, and decided to check out the backlash of these while I had the dial indicator set up. None of these had any *less* backlash. All 6 were "0" stamped, except for one "1". The "1" had more backlash than the others (just more worn?). All of these are used gears, so I'm not sure what all this says. I thought perhaps one gear might have less backlash than the one from the engine and give me some clues.
The spec book shows a measurement technique for measuring the gear alone, using 4.5 mm steel rollers. Now, let me see, where in my meaurement tools drawer, did I mis-place those 4.5 mm steel rollers? The numbers given here are for the wear limit, so if I can ever find those pesky 4.5 mm steel rollers (doesn't everyone have a set of these?), I might get the answer.
What happens when the gears in question are out of the installed spec with regard to the backlash? Cam timing hard to set? Issues with engine performance? Issues with premature wear of something? I can't find any discussion of this "problem"(Is it?).
Replies from anyone with any insight appreciated.