Well here we go, you asked for it. Not much of this will be relevent to your everyday synchro gearbox but you don't get to see one of these every day. Or ever for that matter. There are probably only a handfull in Australia. # Fact. Holinger Engineering, in the mid 1980's were supplied option 1 gearbox's by Nissan Motorsport and were commissoned to turn them into dog boxs with wider gear teeth. Approximately 50 were done all in standard option 1 ratios retaining the origional synchro first.

This one arrived to the fitting room and was handed to me mostly in parts,(missing a few too) and I stripped and crack tested it to see what needed replacing. It was in fairly good condition overall anly needing 4th spline gear replaced. A new spline gear was made and also a drawing was made up to convert it to dog first. It took a few weeks (or more which is normal for us during porche season) but the parts finally came through and onto the bench it went for assembly.

I guess you'll notice that the layshaft has massive coarse splined for the individual spline gears. I am led to believe that the Hewland spline was used for ease of getting gears made at the time. It makes sense to have individual gears so that you don't have to replace a whole cluster when sh!t breaks.




The input shaft had eaten through the case hardening on the spigot roller face so a new sleeve was made to repair the shaft. Not normal practise for us but it would have been very costly to remake a shaft, and time consuming.

So don what are you going to do with this??

customers car im guessing for all those race nissans they are restoring.

he said shaft hehehehe

It's not mine Nick, It is from George Fury's old Group A DR30 Skyline. It came into work. There is no way I could afford one of these.

So the first thing to do is build up the mainshaft, I lube the needle bearings with SAF XA LSD oil whick is the oil we reccommend and 4th dog gear goes on followed by 4th/5th selector hub which is retained by a ground to size washer and circlip.




Then the same applies with 3rd dog gear, no circlip as the rest is retained up the back with lock nuts.




Then 2nd gear bearing sleeve goes on. The things that you don't see are probably the most important. I can roughly calculate how much endfloat a gear will have by measuring the sleeve and gear and allowing for crush of the sleeve determine the endfloat. Approx 0.004" ber side of a gear is what I look for. So 0.008" is good but a little less is o.k. When there are 2 gears sharing a bearing sleeve it would be 0.012" or thereabouts. Sometimes these bearing sleeves can errode through fretting and your endfloat decreases. The hole is for a 5mm ball that located the 2nd gear thrust washer.




Followed by 4th gear and needle roller.

Very interesting, keep the photo's coming.

im glad your working on that thing and not me....i been working on little gearboxes for our german wheelchair hoists as there have been major faults on there stupid gears....they went for a nylon gear instead of a stainless gear like the rest and thats enough to give me the ships with all those baby roller bearings and circlips

why is it called a 'dog' box?

Sorry don thought you'd get a few extra parts made for you so you could build one or turn one of your box's into something like it!!

DD its called a dog bog as it uses dog teeth to engage the gears rather than synchros

they would be the tabs you can see in the first and last pic of that last post

Also cause its sounds like an angry dog :)