Thread: Daihatsu diesel conversion problems

update.......The plate was out by 0.012mm but only up and down (?) the plate was parallel. I managed to get it down to 0.004mm by carefully filing the dowel holes and plugging with locktite and epoxy putty. Anyone reckon this is close enough? The crank has a bit of play like 0.005mm up and down I`m thinking this isn`t helping...any thoughts?

ok first off, are we working in thousandths of an inch or in mm? if in mm you must have a very very fine set of files as you're working on a finer tolerance than my verniers.

assuming its in thousandths of an inch

thats more than close enough, its probably better than OEM specs.

whats important now is to see how the play on the shaft goes and to see if you can replicate the box jumping out by operating the box by hand.

if you have too much float on the support and input bearing for the input shaft you'll get jumping out of gear any time theres enough drag on the output shaft that tries to pull the shafts apart

(have a look at the angles on the teeth, + remember the layshaft is always driving)

Phew! I` was beginning to think I should go and juggle it again.....I`m going to fit the bellhousing and input shaft alone and perhaps try and measure how square the rear of the input shaft in relation to the rear face of the bellhousing, I`m thinking this should be dead on otherwise it will wobble it out of 4th? I`m also assuming that the crank float will be forced down when the engine is running but then again maybe some weird gyroscopics are going on. I centred the adaptor by taking up all float before measuring the eccentricity (the adaptor not mine)
There`s a little play in the input shaft when the box is assembled, no oil leak (amazement) and all the bearings were new 80km ago so they should be OK. I`m not sure about inspecting the 3rd and 4th female splines (on the 3rd gear and input shaft) They look a tiny bit tapered but also look like the steel is harder than that on the synchro hopefully saving them....I have a spare input shaft but it looks identical.....
Thanks Dave your advice is much appreciated (and everyone else...)

worry less about the movement on the spigot side of the input shaft and more about the back and forth movement of the shaft in the box.

remember that the input and out put bearings cantelever off of themselves on the center support bearing as well as get their "preload/endfloat"

a lot of movement on the spigot side of the input doesnt equate to a massive amount at the center support bearing and its more of a problem if the input shaft is running "off center" which it appears yours isnt. My next line of thought is that when the box is running the various thrusts being created from the input shaft, the lay shaft and the output shaft is enough to cause the 4th gear syncro to disengage enough to allow the baulking ring to throw it back out of gear.

Just been out to the shed in my PJ`s seems like no back and forth movement, a little on third gear which measured fine when I replaced the distance piece. The thrust washers were within tolerance. I replaced the rear bearing (in the transfer box) but not he outer race (couldn`t work out how to get it out and it looked ok) I can`t feel any wobble in the shaft (its engaged in the input shaft). The layshaft has no endfloat either...
By the way I thought I was in mm but my feeler gauge has no units(!). I used them with a bar bolted to the flywheel to compare clearances and tried to get spot on but settled with much better than before...

Did you check the synchro unit to make sure it is the correct way around while you have it apart.

I would go with that

I once had a centre PTO ( it fits on the back of the transfer box ), it had a fault causing the gearbox to jump out of 4th.
I put the blanking plate back on and the problem went away. Look at the bearing inside that blanking plate.
So that backs up what Dave has said about bearings.
You haven't got a wrong size bearing some where ?

Can you tighten up the thrust washers in the engine? as any increased crankshaft end float could be moving the input shaft to and fro a fraction, walking the 4th gear coupling apart under load.
I have had PTO's on tractors disengage when the implement's drive shaft hasn't been sliding freely and again it was causing the coupling to walk apart, with the transfer of the fore and aft movement into the PTO dog clutch.

Double check the linearity of the centre line of the crankshaft to the centre line of the gearbox mainshaft, as any slight tilt at all of the input shaft will walk that coupling apart .
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