Offroad gearbox build

[idw]

Did you work out what the clutch noise was?

 

[NachaLuva]

Well done!

 

[El_Freddo]

I don't mean to doubt you Alex, I'm sure you're spot on but I want you to really be sure - have you fitted the diff with the pinion shaft in place and roughly lined it all up to see if it really is going to clear - it only takes a tiny bit of movement to make things go astray.

I'm only asking as I've never heard of a crown wheel not being shaved even a little bit with the 1.59:1, I'm sure phiz still shaved his a bit (it's been sometime since I've read his thread!)

Keen to see a 4.44 crown shaved to fit the 1.59:1 low range - that would be the ultimate setup! But I think that also requires chasing down a turbo gearset as they're wider than the NA gearsets - with a 4.44:1 diff ratio it should pull them back into a good spectrum for an NA application.

Cheers

Bennie

 

[Ratbag]

^ Gidday DM

If I were you, I would take great cognisance of Bennie's thoughts on this, and double check all your working clearances against standard clearances.

In theory, shafts shouldn't flex, and bearings don't wobble. In reality, they all move around a bit, specially when under extreme pressure.

Don't find out that Bennie was right by breaking your gearbox ...

I know it's different, but with the head, valve and camshaft modifications I made to my Morris 1100 all those years ago (Good God, it was nearly 50 years ago ... !!). A BMC Works 1340 cc racing Cooper S was running stronger inner and outer valve springs, and bigger exhaust valves than I was. I used standard outer springs with the racing Cooper S inners. My exhaust valves were stage 2 (not stage 5) and my inlet valves were stage 6 - as large as they got.

Without knowing the risks, I ran a 25-65° full race cam vs the Cooper S cam which was a 20-60 (inlet and exhaust valves open for 270° each out of the total of 720°; this compared with 260° for the racing engine). This leaves less than 360° for the full compression and power strokes, even after allowing for the overlap when the inlet and exhaust valves were open simultaneously.

The lift measured at the valves for mine was 0.40" vs 0.38". How close the valves came to the piston crowns, and each other, beggars the imagination!

Anyway, it worked. The car went like the clappers (relatively speaking) - with a standing quarter mile time of around 17 seconds from an 1100 cc engine in a car weighing 16 cwt tare ...

The crankshaft lasted nearly 40,000 miles before it broke in two (three bearing crank ... ), and by then, the case hardening on the camshaft was starting to break up. IOW, the engine was rooted. I fixed the broken crank, then traded it in on a Wolseley 24/80 MkI almost immediately ...

The lesson? Don't push things too far!

You might be dead lucky and get away with it, as I did for quite a while. Chances are far higher that you won't, and it will end in tears.

Check and double-check all the clearances for thrust washers, bearing play in all shafts, gear play on the shafts, synchro ring engagement. Do a dry run (or three ... ) with the gearbox open but fully assembled.

Far easier to take it apart and do it again than it is to fix a badly broken box ...

Just FWIW.

 

[Dedman]

Your photo is actually an excellent example of how synchro rings work as well as constant mesh gears. Do you mind if I use it at some stage for that purpose?

Yes that is fine

No machining on the synchro ring…

This was one of the areas where I used that ingenuity I was speaking of. To take some off the outside of the syncro sleeve I remount the syncro hub on the L series shaft in the L series case without any of the low range gears. I put the sleeve on the hub and packed it a bit so it couldn't slide off. By doing this the syncro sleeve was able to freely rotate on the l series shaft bearings which has a very similar effect of mounting the syncro sleeve on a lathe.

Next I set up a hose to trickle water over the syncro sleeve to keep it cool whilst I ground some material off.
To do the actual grinding I just gave the L series shaft a turn by hand and whilst it was still spinning I carefully applied the grinder (with brand new perfectly flat disk) to the syncro sleeve. The friction from the grinder make the shaft rotate faster (1000+ rpm) so material is removed very evenly and by carefully holding the grinder flat a very neat result is obtained.

This is something I have done many many times successfully before on other parts and projects but I wouldnt recommend others try it as it is very difficult and very dangerous (water and metal filling flying everywhere including covering a 240V angle grinder....)

Did you work out what the clutch noise was?

What noise?

 

[Dedman]

Have you fitted the diff with the pinion shaft in place and roughly lined it all up to see if it really is going to clear

Yep I have put it all into the other half of the casing with the diff and it clears, looks to be about a millimetre of clearance I have also assembled the two halfs (although I didnt put any bolts in) and it seems to be fine, sounds like something is scraping a tiny bit but it might just be lack of oil,

I'm only asking as I've never heard of a crown wheel not being shaved even a little bit with the 1.59:1, I'm sure phiz still shaved his a bit (it's been sometime since I've read his thread!)

I was following phiz's thread very closely and there was no mention of touching the crown wheel. Same for the thread on AUsubaru you pointed me to.

Keen to see a 4.44 crown shaved to fit the 1.59:1 low range - that would be the ultimate setup! But I think that also requires chasing down a turbo gearset as they're wider than the NA gearsets - with a 4.44:1 diff ratio it should pull them back into a good spectrum for an NA application.

Cheers

Bennie

That's what I want, the ultimate setup :ebiggrin: I think I really only need to change 5th gear slightly so im not revving my tits off on the freeway. The donor 4.44 box should have a good option which will keep freeway revs about the same as current and the gap between 4th and 5th will still be smaller than an SG forester

 

[Dedman]

If I were you, I would take great cognisance of Bennie's thoughts on this, and double check all your working clearances against standard clearances.

Any Idea where to get these standard clearance numbers? Whilst it might be good to compare these clearances in reality I know that I have far less than standard clearance so all I can do is make an assessment on if it is sufficient or not.

 

[jf1sf5]

Yep I have put it all into the other half of the casing with the diff and it clears, looks to be about a millimetre of clearance I have also assembled the two halfs (although I didnt put any bolts in) and it seems to be fine, sounds like something is scraping a tiny bit but it might just be lack of oil,

You should assemble the 2 halfs and bolt them together within specs but without silicone joint to be sure everything clears the ring and move the LR lever…I had to do it twice !

 

[Dedman]

You should assemble the 2 halfs and bolt them together within specs but without silicone joint to be sure everything clears the ring and move the LR lever…I had to do it twice !

Its on the to do list, after I have tried to get the 4.44s and front LSD in.

 

[Ratbag]

Gidday DM

What I was talking about (not very clearly ... ) was that you need to ensure that the various thrust washers have exactly the right clearance (this prevents gears moving along the shafts when under load); and that all bearing play (radial tolerances) are well within spec (this prevents shafts and gears from moving away from each other when under load, also allowing the gears to become both misaligned and not engage properly with each other).

Constant mesh, helical cut, spiral gears are designed to have a 3:2 tooth mesh at all times. If bearings and layshafts (aka 'countershafts'; also aka input shaft/first motion shaft, second motion shaft, third motion shaft and output shaft) have any looseness or radial play, it allows these to change their perfectly straight alignment to meshing at an angle, or allows the gears/shafts to move away from each other, the gearbox will destroy itself in a very short period.

Holdens and Falcons (in my youth - 40+ years ago) were renowned for the weakness of their layshafts and layshaft bearings, along with the inadequacy of their secondary gear sets. IOW, if you drove them hard in the intermediate gears, they would break. Some of my friends managed to do this about every 5-10,000 miles! In top, they were straight-through drive (i.e. no overdrive - just a 1:1 input/output shaft relationship), the input shaft and output shaft were locked together in top gear. In this position, the boxes were quite robust. In the intermediate gears, they were weak as the proverbial.

 

[Dedman]

Cheers RB, yeah I didnt get that from your first post at all. Yes I am checking all that as best I can and if I am not confident I will get a professional to check it.

On another note I ordered a donor box for the 4.44 gearing, front helical lsd, DCCD and taller 5th gear. Now I have all the parts I should need for the build.

The box came as a package deal with a rear suretrac LSD. No Idea if it will be a direct bolt in or not but I will just flog it if its not. Has anyone had any experience with one of these suretrac diffs off road? I cant imagine they would be anywhere near as good as a plated diff but still better than an open one.

 

[NachaLuva]

Awesome! Any info on where/how much you got the box from?

I think Suretrac is a version of a helical diff, will still work well but not as good as a plated diff

 

[Rally]

Suretrac overheats and gives up.

 

[Dedman]

Gearbox done

Hi Rally. Is this experience from a rally situation or proper off-road driving? I am very intrigued how it will go off road as I really have no idea how the diff works...

Suretrac overheats and gives up.

The box is out of a Version 6 RA, Japanese import by a mob in QLD. Was sold as "in great condition" but when it arrived it had a faulty centre diff coil and a bearing gone in the transfer case. Was not happy... After discussing with the seller I managed to get a partial refund which made it a relatively cheap box.

Last weekend was a huge weekend of gearbox building, 30+ hours of solid work. Came out of it with a completed box ready to be installed. Managed to get everything I wanted in to it. L series low, front helical, 4.44 final drive with .825 5th to compensate and DCCD centre which I rewound myself.

I had to take a fair bit off the 4.44 crown wheel to get it to fit so it will be interesting to see how it goes and how noisy it is.

Now to find time to install it and try it out. Unfortunately wont be for a few weeks though. It is going to be a very tense moment driving for the first while as this is the first gearbox I have built and for all I know it may explode under load...

More pics to come when I get a chance

A few things to note for anyone else doing this.

This front helical diff had axles that go into the gearbox with spring clips to hold them in. These did not come with the box and I had to shave the ends off the forester ones to get them to fit. I also had to take a tiny bit off the circlips.

To get the DCCD to fit you need both transfer gears and the rear housing of the DCCD transfer case. They will not fit in the standard AWD transfer case. This may not be true for pre 1999 boxes which had the earlier style centre diff but AFAIK you will still need at least the lower transfer gear.

Swapping the 5th gear from the RA box to the SF box is a bit of a pain and the synchro needs to be swapped as well and the internal diameter is different. The RA synchro is also a different style, the same as the synchro on the low range.

To get the 4.44 to fit with the L series low mean you have to take a lot of the crown wheel. I think it should be fine but I would recommend that you wait and see if my box fails before trying this....

 

[jf1sf5]

To get the DCCD to fit you need both transfer gears and the rear housing of the DCCD transfer case. They will not fit in the standard AWD transfer case. This may not be true for pre 1999 boxes which had the earlier style centre diff but AFAIK you will still need at least the lower transfer gear.

Well done Dedman !

On the '97-'98 SF's, the DCCD housing is a direct swap, yours must be a '99+ gearbox ?

Now you have the most 4WD gearbox one can have in a Subaru !

 

[Dedman]

Well done Dedman !

On the '97-'98 SF's, the DCCD housing is a direct swap, yours must be a '99+ gearbox ?

I thought that might be the case. Im very happy with the way it turned out though. Good thing I bought the whole DCCD gearbox and not just the diff!

You just reminded me of another thing I did. The 99+ boxes had the return to centre gear selector springs inside the box where as the RA has the external return to centre spring. I took the whole return to centre arrangement from the old box transfer case and put it in the new one.

Now you have the most 4WD gearbox one can have in a Subaru !

Haha I am not going to say that until I test it and check it works.

 

[Rally]

The overheating of the Suretrac overheating issues came to light from circuit racing. After about 2 or so laps, the diffs would open up. With regards to the front helical diff, my axles went straight in. It all depends on a bit of a lottery as to whether or not the diff you source for your car mates up with the axles. Some do, obviously not all.

 

[NachaLuva]

Exc work, well done

To get the DCCD to fit you need both transfer gears and the rear housing of the DCCD transfer case. They will not fit in the standard AWD transfer case. This may not be true for pre 1999 boxes which had the earlier style centre diff but AFAIK you will still need at least the lower transfer gear.

So if I got the transfer case complete that would be all I need? I'm p[lanning on putting this in an SG box...

 

[Dedman]

Yeah for an SG box a complete transfer case swap would be your best option. Bare minimum you would need the diff, both transfer gears and rear of transfer case housing.

 

[Dedman]

My new exedy heavy duty clutch arrived today and picked up a new pilot bearing to go with it as well. Looks like the box is going in this weekend :ebiggrin:

I also grabbed a speedo corrector kit from Jaycar so I can accurately compensate for the change in final drive ratio and get the speedo within 1% of what it is meant to be.

https://www.jaycar.com/productView.asp?SUBCATID=965&CATID=76&ID=AA0376&URL=index