FJ20 Gearbox / Clutch Issue - Help needed

[PLAYA]

Yea but there is 2 dowels, the bolts only hold the box on they dont locate it. Do you have the 2 original dowels?

[tim510]

1 mc-dowel in the block

[tim510]

so I've bought a dial gauge and a magnetic stand for it....



what do I do next :D

[TurboRA28]

Reading with interest as I have somewhat similar problem with a custom adapter plate.. But potentially could simply be a bad gearbox in my case.. Kicking myself for changing too many things at once.. Hindsight says I should have put original box back in which I knew was quiet.

[jmac]

get a high tensile bolt with a 3-4inch shank but the right thread to suit a flywheel bolt, with any luck you'll be able to anchor the dial indicator to the shank, if not, make up a sleeve or whatever it takes to do that, inster bolt, tension up so it bottoms out in threads and attach dial indicator linkage (leave 1 or 2 of the arms on there) fit the gearbox, then manouver the dial indicator so the 'finger' is on the snout of the gearbox (the support for the clutch throwout. then slowly turn the crank, and watch for the reading on the dial to fluctuate. Note the max and min reading and at what 'clocking' they occured at.

let us know when you get to that point.

[tim510]

get a high tensile bolt with a 3-4inch shank but the right thread to suit a flywheel bolt, with any luck you'll be able to anchor the dial indicator to the shank, if not, make up a sleeve or whatever it takes to do that, inster bolt, tension up so it bottoms out in threads and attach dial indicator linkage (leave 1 or 2 of the arms on there) fit the gearbox, then manouver the dial indicator so the 'finger' is on the snout of the gearbox (the support for the clutch throwout. then slowly turn the crank, and watch for the reading on the dial to fluctuate. Note the max and min reading and at what 'clocking' they occured at.

let us know when you get to that point.

that all makes sense....

I'm not 100% sure how I'm going to read the gauge when it's hidden inside the bellhousing... im considering using a small camera and recording it.... I can get vision through the clutch fork hole and through the starter motor hole...

[townie :)]

hmmm was doing some searching and found a paragraph that rings a slight bell.

There is a bit of confusion over the larger front bearing that Nissan decided to use in the series 3 Bluebird and all RB 71 boxes .
I think they found that the extra torque from the larger NA engines ie RB30E and smaller turbo sixes like the RB20DET was overloading the lower or counter shaft/cluster gear front bearing .
What they did was bore a larger lower hole in the gearboxes bell housing and fit virtually the largest bearing they could in the space available . If you could see a large and a small hole pair of bell housings side by side its very obvious because the distance between the holes is very small with the large lower bearing type .
The bearing journal size on the counter shaft is the same so from that perspective they are interchangeable .
It's entirely possible to have a small hole type bell housing ie FJT bored out accurately enough to fit the larger bearing though you need to also use the front bearing retainer/clutch bearing spigot plate because its machined to suit the larger bearing . These are found in RB type 71 boxes .
I found this out because I wanted Jacko to get an RB20 turbo box behind an FJ20 in a Bluebird and don't like this "slotting" of the RB type bell housing to fit the FJ20 blocks top bolt spacing . The real problem is that the top dowel hole is also differently located on an RB housing compared to an FJ one so you have to flick it and risk miss alignment in the cranks pilot bearing .
Stu's suggestion was to bore the FJ's bell to suit the larger lower bearing and re use the RB ones front bearing cover plate . It all works factory style using a std bearing and seal .

Full thingy here.
http://www.bmsc.com.au/forums/rallyi...gearboxes.html

Could be a better option but I am unsure about enlarging the hole or whatever, someone with the right equipment might be able to do it for cheap?.

[tim510]

hmmm was doing some searching and found a paragraph that rings a slight bell.



Full thingy here.
http://www.bmsc.com.au/forums/rallyi...gearboxes.html

Could be a better option but I am unsure about enlarging the hole or whatever, someone with the right equipment might be able to do it for cheap?.

rbman, I'm up on the FJ-RB bell housing convertion, but a few things stopping me from doing that.

1. I don't have a donor bellhousing.
2. I don't want the added expense to get someone to modify the FJ bellhousing (they will tell me it's a shit idea and I should spend $1000 to rebuild the inferior FJ20 donor box)
3. I don't want to split the RB25DE box I have. Fucking thing cost me $1100 and I don't want to open it up!

[jmac]

Shit I just realised - additional instructions - check which type of crank is used in these engines. In some the flywheel bolts go into blind holes (if so, do as instructed) on others, the flange is wider than the crank tail and so the bolt holes/threads go all teh way through, and if the threads on teh bolt are long enough, it can go through the crank flange, and actually hit the back of the block stopping it from being able to be spun. If it is the latter, you either shorten the threads on the bolt, or add a nut and lock it once there is sufficient bolt engagement with the crank flange threads.

[tim510]

ok so I had a go at measuring this thing...

these measurements were taken with the engine attached directly to the gearbox, no backing plate (better access to the gauge + adjusters).

I set it up the way JMac suggested. The dial gauge attached to the crank... I wasn't able to get a solid reading, I couldn't get the gauge's tip to reference correctly and the reading would change as the weight of the gauge acted on the tip of the gauge, the adjusters weren't tight enough....at 12oclock it read hugely different from from 6 oclock...

edo spec photos of the first attempt:


dummied up on my clutch tool



so then after skinning my knuckles and getting rather pissed off, I decided to rig it up a bit different, I'm not entirely sure if this reading has any merit (critique me!) but it made sense to me...

In both sets of photos the block and box are upside down, it was easier to set it up this way..

I attached the dial gauge and it's magnetic base to the block and measured the input shaft (it had a smooth section that was perfect)... I popped the box in-gear and rotated the yoke... it had a total variation of .2mm... This crank also had no spigot installed, so the input shaft was floating.






thoughts? feedback?

[jmac]

thoughts - whiskey tango foxtrot. You won't get any meaningful reading reading a dummy inputshaft in the crank, because the spigot bush will have enough slack that it can droop.

You have the dial indicator attached correctly to the crank, BUT you need to put the finger of the dial indicator onto the 'snout' of the ACTUAL GEARBOX, or any other concentric/centred on gearbox axis point.

like for example if the input shaft was totally out of the gearbox, and the input shaft front bearing, you could run the dial indicator finger in the 'hole' where the bearing is pressed into, which is centred on the box (since wherever it's drilled that bearing slides in and locates the input shaft)

I haven't got any webspace any more but I can do a picture if you need in mspaint and email it to you and you could upload it or something.

[tim510]

thoughts - whiskey tango foxtrot. You won't get any meaningful reading reading a dummy inputshaft in the crank, because the spigot bush will have enough slack that it can droop.

You have the dial indicator attached correctly to the crank, BUT you need to put the finger of the dial indicator onto the 'snout' of the ACTUAL GEARBOX,

yeah sorry, just a photo of my dummy up... i was attempting to get a reading from the throw out bearing slide snout... I understand a limp-dick input shaft won't give me a reading...

was my 2nd setup useful at all? i can't see why that wouldn't be accurate...

[jmac]

no, it's still wrong.

You need the dial indiactor attached to the crank like in the top picture, so that the WHOLE dial indicator turns around with the crank. THEN you manouver the dial indicator so the finger is on the throw out bearing slide snout (to use your terminology)

Send a pm with your email addy and I'll do the mspaint and send it.

[tim510]

john, I understand how it needs to be setup..

I had it setup in that way but had difficulty getting it aligned correctly... the point on the dial gauge likes to be at 90degrees to what your measuring..

I couldn't get the dial gauge to tighten on it's bracket so when it rotated the reading changed, not because of mis-alignment, but because i wasn't able to get the instrument to stay still...

I'm going to have another go tomorow...

again, is the 2nd measurement I took of any value?

[jmac]

Which pic is the second measurement? FRom what i can see, none of them thus far are of any use as far as checking the alignment. it's the snout you need. The input shaft will go into the spigot and try and attain angularity to satisfy both axes, you need the snout instead which is rigid and allows a true representation of any mis alignment.