g'day punters, west aussie here. i have a hjz79 needing a new gearbox as they do. its a bit of a roughy ex miner; just a work ute, and im looking for a cheap fix. just wondering what other boxes people have fitted and any links to such threads. seems the turbo diesel 6 a popular option. have a free 80 series wagon box at my disposal; anybody done this? or other ideas?
HZJ79 replacement gearbox options?
- Thread starter west aussie
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Gear box.
Gee this is a late model for you
back to the question.
They are a bit week those boxes. One of the hire companys here fitted HZJ75 series boxes to their 78/79 cars.
They used the 79 t/case [fill the extra bolt hole in]
lenghten or shorten the drive sharfts.
Make a c shaped gearbox crossmember.
Use a 75 gearbox cover on the floor.
They converted about 10 cars and worked well.
Even got a blue tag for the job.
Gee this is a late model for you
back to the question.
They are a bit week those boxes. One of the hire companys here fitted HZJ75 series boxes to their 78/79 cars.
They used the 79 t/case [fill the extra bolt hole in]
lenghten or shorten the drive sharfts.
Make a c shaped gearbox crossmember.
Use a 75 gearbox cover on the floor.
They converted about 10 cars and worked well.
Even got a blue tag for the job.
- Thread starter
- #3
don't you hate working on late model when there so many more interesting old tojos laying neglected in the same shed! ive only recently ventured away from the 25 page haha, but guess 2H is the main game here. HZJ box was my original idea but don't have one to hand. (seems HJ75 and HZJ75 have different input shaft in length as well as clutch spline). i've pulled this 80 box and reckon its worth a closer look. would love to get away without fabricate a new crossmember but we see. its a roughy ute and want a cheap fix. also got the number of a 4wd wrecker in perth who has supposedly done this conversion couple times so call him tomorrow. thanks for the input will let you know. and if anyone else wants to chime in that be great.
- Thread starter
- #4
well punters, the combination of want of better ideas, budget of $0, and a need to get this ute going i decided to leap in the deep end and have a go. anyways todays work seems promising at least, got the big lump bolted up to the motor and it fits in the hole at first glance. at present is sitting on a jack with a couple bellhousing bolts done up. spoke to a couple of people today who have heard of this conversion but nobody who has actually done it. i went rough early; ran old clutch and thrust bearing, took a cold chisel to the floor... will have to modify crossmember as the 80 box will want to mount a little further forward. rough is fine; its that sort of ute (and budget). will take my camera tomorrow in case i can make this work the info may be of some use to others. i also hear tobay there are several variations of 80 wagon boxes; though all internal differences? anyways if i can make it work i am happy to have shafts fabricated as i am done with the original HZJ79 box. done with HZJ79 altogether truth be told. also have a blown front diff. anyone know if my donor 80 wagon diff gonna fit?
If your talking about just the front diff center, then yes it will bolt straight in. No dramas there.
The rear on the other hand will bolt in but the 80 has a 30 spline axle compared to the 79 which has a 32 spline axle. Long story short, axles won't go in
The rear on the other hand will bolt in but the 80 has a 30 spline axle compared to the 79 which has a 32 spline axle. Long story short, axles won't go in
Hzj 80 is 4.1 not 4.11
If you have both diffs fit both then the gearing will be right.
- Thread starter
- #8
thanks for the input. so seems i would need to run both diffs and also 80 rear axles? i can check this if i pull them anyway. wrote a big post here last night but lost it while posting somehow so gave up. anyways the gist of it was i got this conversion up and running yesterday. in summary i used
80 box, bellhousing, thrust bearing and clutch fork.
80 spigot bearing; they are different
79 clutch slave and pushrod
80 gearbox mount bolted to the 79 crossmember
had to lengthen the 2 gearbox mount holes on the crossmember with the oxy so that the mount could ride about 10mm further forward. melt away carefully doing this as this piece is 2 thin layers so if you go too hard with the oxy it blows crap out of the top layer.
had to butcher the flor a bit (but i butchered it a lot!) will post some pics later so that if anyone else tries this they can be neater than me. both 80 sticks fit well and are comfortable to use without modification
80 box, bellhousing, thrust bearing and clutch fork.
80 spigot bearing; they are different
79 clutch slave and pushrod
80 gearbox mount bolted to the 79 crossmember
had to lengthen the 2 gearbox mount holes on the crossmember with the oxy so that the mount could ride about 10mm further forward. melt away carefully doing this as this piece is 2 thin layers so if you go too hard with the oxy it blows crap out of the top layer.
had to butcher the flor a bit (but i butchered it a lot!) will post some pics later so that if anyone else tries this they can be neater than me. both 80 sticks fit well and are comfortable to use without modification
- Thread starter
- #9
ran the 79 tailshaft without modification but my gut feeling tells me it may be the tiniest bit long. need to measure the available spline travel on a stardard 79. fine for a test drive but wont be doing any jumps with a pallet of cement on the back just yet. sure 79 front shaft will be fine but need to sort my diff issue. anyways happy with the conversion not so much with the donor box it has a few issues. it came from an anonymous meekatharra highway wreck after all. put the seats in loose and test drove the 12 mile to town last night for stores and a beer. the grinder cut floor folded up out of the road and red hot air blowing up past the sticks played havoc with the backpackers ankles. thanks again and will try get a pic up soon of the floor cuts
Yes your right, I stand corrected.
The thing with using the 80 series axles is they will be too long to fit in the 79 series housing.
You can't run the rear 80 series ring and pinion in the 79 series carrier because the bolt pattern is different.
IMO theres 2 ways you can go with the parts you have.
1. Fit the complete 80 series rear end. Involves alot of cutting/welding. Not to mention the track difference.
2. Use the complete 80 series rear center, fit the 79 series side gears to allow you to run your standard axles. You will need to machine the part where the axles go through the housing 1.5mm to give you clearance. This is the simplest way.
I know the second way works because I'm running 80 series ring and pinion (3.727 ratio) in my hdj79
Hope this helps you out.
- Thread starter
- #12
ok i try post a couple of pics
- Thread starter
- #13
this computer stuff drives me mad but got it to work eventually. first shot above is my butchered trans hump where i chiseled the spot welds out. this was pretty much the state of affairs on my first test drive to town no need to be this brutal but i was rushed for time and had a small window off opportunity when there a couple able hands about to help me get the big lump in position. 2nd shot is the 80 4wd lever that needs to be removed before fitting. i try some more
- Thread starter
- #14
ok without chiseling the trans hump off i reckon these (above) are the cuts i could have got away with. gearstick, transfer lever and a general view. trans cut needs to be large enough to reinstate the lever assembly. and hopefully below a look with the patch pieces glued and screwed into place
- Thread starter
- #15
and the slight nitching of the holes where the gearbox mount meets the crossmember. once the goo sets tomorrow i reinstate the floor covering and 80 series boots. am yet to measure driveshaft travel on an unmolested example but if slight modification needed i am thinking just to slice a small amount off the male spline to prevent it ever bottoming out
Nice job done! Do you have any issue of running the speedometer?
Look like you need some attention on your floor pan.
- Thread starter
- #18
i'll put it this way; i don't have any issue with not running the speedometer haha. the speedo wires plug right up and i did this with no joy on my first test drive. reverse and 4wd wiring is just tied up out of the way for the moment; i haven't even checked if the plugs mate up. i will get to this but wont try too hard wiring is really not my thing. pretty sure the speedo was working before the box failed so will see if the 79 sender will fit the 80 box. this may even make up for the difference in diff ratio. think i've decided not to bother with the diff conversion thanks to all the good info posted here. just keep my eye open for a replacement 79 diff or see if any of my knowledgable friends think my existing one is rebuildable. just need all my options sorted before i open it up and render this pos undriveable again. nothing like a rusty ex miner 79 to demotivate when there a 25 and a fleet of 45, 47 and 75 that all need more love than they get. will get back when i studied the speedo situation more
- Thread starter
- #19
ok had a play. discovered the needle that drives the speedo sender broken in the donor 80 box. swapped in the 79 needle and sender but still no joy. these units are identical and there is no reason for this not to work. the needle turns exiting the box so the problem is electrical and downstream. i was pretty sure the speedo worked previously; perhaps i was wrong or perhaps we damaged a wire somewhere pulling the old lump. this must be an easy fix though. got both reverse and 4wd light working. used the 79 switches so the wiring meets up with the plugs on the original harness. the switches are different at a glance but the difference is in the amount of travel in the switch (the 80 has more) and not the overall dimensions, but all works fine. will play with the speedo further down the track but absolutely sure it is all easily doable
Thank you for your information ^^