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Prado 95 transfer case issue

Tee Jay

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Aug 22, 2023
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new_zealand
I'm pulling my hair out! My Prado has a worn out transfer box and I can't find a replacement. Can someone help with some information? It's a 2002 J95 1KZTE Manual trans, no ABS, no
traction control, it has a rod-shift centre diff-lock system (no actuator motor), does anyone know if a 1kz hilux case will fit, will an Auto case fit, or can anyone suggest an alternative? I'm struggling to find any information online. I live in NZ and most Prados here are Auto trans. Thanks in advance.
 
Hilux is not an AWD system. So unlikely to fit the Prado's shafts even if it will mount ok to the tranny.
 
An Auto transfer box won't work either - the selector shafts for high/low ratio and centre diff lock stick out of the front whereas on a manual they are inside. They can be converted (I have done a couple) so if you can find an Auto TB in good condition you could swap the selector shafts over with your old one.

Other differences:- The Auto TB doesn't have synchromesh on low ratio (the manual does) and there is an extra detector switch on the Auto that you could ignore.

Rebuilding a TB needs care, I'm afraid I'm in Edinburgh UK so not really able to help - apart from advice and pictures if you're stuck !

Good luck.

Bob.
 
There are quite a few 4WD wreckers here on the east coast of Australia and I've seen quite a few manual tranny 1KZs about. Could the 120 1KZ manual transfer case also fit I wonder - the 120 diesel was 1KZ for a couple of years here at least.

I know shipping will be a PITA from here but slightly easier than from Europe/Japan maybe.
 
An Auto transfer box won't work either - the selector shafts for high/low ratio and centre diff lock stick out of the front whereas on a manual they are inside. They can be converted (I have done a couple) so if you can find an Auto TB in good condition you could swap the selector shafts over with your old one.

Other differences:- The Auto TB doesn't have synchromesh on low ratio (the manual does) and there is an extra detector switch on the Auto that you could ignore.

Rebuilding a TB needs care, I'm afraid I'm in Edinburgh UK so not really able to help - apart from advice and pictures if you're stuck !

Good luck.

Bob.
Thanks Bob, really appreciate you giving me this info. If I found an auto TB would I need to take it apart to fit the selector shafts, or would they slot in? Also, is there a disadvantage to not having a synchromesh on low ratio?
 
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There are quite a few 4WD wreckers here on the east coast of Australia and I've seen quite a few manual tranny 1KZs about. Could the 120 1KZ manual transfer case also fit I wonder - the 120 diesel was 1KZ for a couple of years here at least.

I know shipping will be a PITA from here but slightly easier than from Europe/Japan maybe.
That's a good point, I believe the earliest 120s in NZ did have the 1KZ. Thanks for that.
 
Thanks Bob, really appreciate you giving me this info. If I found an auto TB would I need to take it apart to fit the selector shafts, or would they slot in? Also, is there a disadvantage to not having a synchromesh on low ratio?

I'm afraid its a full strip-down to change the selector shafts, plus they have an interlock mechanism at the rear that can be tricky.

On a manual GB/TB you are supposed to be able to engage 'Low' at 5 MPH - that's what the Synchro if for. On an Auto you have to be stationary with the drive in neutral before engaging 'Low' - it objects loudly if you try anything else (well, my Auto '100' does, I assume the '90' is the same - mine is a Manual).

The Selector shafts sit above the main epicyclic gear cluster and the assembly has to be inserted 'as one' - pictures:
 

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Thanks Bob, really appreciate you giving me this info. If I found an auto TB would I need to take it apart to fit the selector shafts, or would they slot in? Also, is there a disadvantage to not having a synchromesh on low ratio?

I'm afraid its a full strip-down to change the selector shafts, plus they have an interlock mechanism at the rear that can be tricky.

On a manual GB/TB you are supposed to be able to engage 'Low' at 5 MPH - that's what the Synchro if for. On an Auto you have to be stationary with the drive in neutral before engaging 'Low' - it objects loudly if you try anything else (well, my Auto '100' does, I assume the '90' is the same - mine is a Manual).

The Selector shafts sit above the main epicyclic gear cluster and the assembly has to be inserted 'as one' - pictures:

Thanks Bob, I think a full strip-down is a bit beyond my skill-set, looks like I'm gonna have to find a manual TB.

I took the front drive shaft off yesterday thinking it would be better if I ran it in 2WD to bypass the transfer setup, when I went to take if for a test run it wouldn't move. I went through all the gears with no throttle and there was no forward movement. I gave it a bit of gas, but still nothing. I could hear the front output shaft turning, and that was it. There was also a slight vibration, which got worse as I selected a higher gear. I was puzzled to say the least, so I thought I'll try it in HL to see what happens, and it drove off perfectly. I tried it in H again, and I got nothing again. Does this mean that the TB is more than just worn out? Does driving it in HL pose a risk at all, will it cause any further damage? Will I be able to use it like this until I get a replacement TB?

Thanks in advance
 
Yes HL (centre diff locked) would be needed if you've disconnected one of the driveshafts. Otherwise the centre diff will drive the easiest one, the disconnected front drive, and it'll be double the usual speed hence the vibration possibly.

I am not a mechanic but I don't see this causing damage. It's RWD only of course so probably don't want to go extreme off roading. I'd do the same on my own rig and probably leave it 10kkm until I get off my arse and fix it.

The rear axle is the strongest one anyway.
 
You won't do any harm running on the rear prop with the Centre Diff locked, just treat it as a road car.

It would be interesting to see what happens if you reverse the process - remove rear prop, replace front prop and run with the Centre Diff locked. This will put all the drive through the Hi-Vo chain and the front wheels. If the chain is the cause of your problems expect some loss of drive and nasty noises. Don't run it on the road like that, the front diff is known to be weak and you have problems enough !

Bob.
 
Yes HL (centre diff locked) would be needed if you've disconnected one of the driveshafts. Otherwise the centre diff will drive the easiest one, the disconnected front drive, and it'll be double the usual speed hence the vibration possibly.

I am not a mechanic but I don't see this causing damage. It's RWD only of course so probably don't want to go extreme off roading. I'd do the same on my own rig and probably leave it 10kkm until I get off my arse and fix it.

The rear axle is the strongest one anyway.
Thanks mate, I actually don't go any extreme off-roading, the nearest I get to it is crossing a patch of grass and the odd gravel road. You make an interesting point about the vibration, that it could be attributed to a higher output shaft speed.
 
You won't do any harm running on the rear prop with the Centre Diff locked, just treat it as a road car.

It would be interesting to see what happens if you reverse the process - remove rear prop, replace front prop and run with the Centre Diff locked. This will put all the drive through the Hi-Vo chain and the front wheels. If the chain is the cause of your problems expect some loss of drive and nasty noises. Don't run it on the road like that, the front diff is known to be weak and you have problems enough !

Bob.
Thanks Bob, I'm actually beginning to think that the problem may not be entirely in the TB, or may not be there at all.

'Adventure Wagon' raised a good point, he said that the vibration I get might be down to higher output shaft speed due to the front drive-shaft being removed, which makes me think that the problem could be in the front diff.

The reason I removed the front drive shaft was to by-pass the TB, thinking it was worn out. The problem I had, was a banging under the floor when I lifted the clutch during gear changes and when I was easing on and off the gas, It was like someone was hitting the tunnel with a rubber mallet. I checked all the gearbox and diff mounts, and the UJs on the shafts and it was all fine, I even installed new gearbox crossmember mount just in case. The banging problem went away when I removed the shaft, but I had that progressive vibration in the output shaft when going through the gears in H whilst not moving forward an inch, which lead me to further conclude that my TB was worn out. It's worth pointing out that at idle speed the vibration is not there in 1st gear and only starts becoming noticeable in 2nd gear, again with the car not moving at all.

So for me, this raises a few questions: Does the vibration indicate a problem with the TB? Is there a way to check the TB condition? I see from some schematics online that the diff-lock is engaged by a 'diff-lock sleeve' that slides on the shaft, is this sleeve strong enough to take ongoing torque from daily use without giving up?

I'll start looking around for a front diff in the meantime, does anyone know if they differ in ratios between auto and manual?

Thanks all
 
Are you leaking oil from the front diff input shaft and/or the TB front output shaft ?? A worn-out bearing in either place would cause vibration. You say that the propshaft UJs are fine, they can be a source of vibration when worn.

Loose propshaft bolts would also cause vibration.

The Centre Diff Lock sleeve is a substantial lump of steel, I think it will survive any abuse, let alone normal running on one propshaft.

Thumping when taking up the drive (manual clutch) could be the exhaust system hitting somewhere - have you checked this ?

I had 'thumping' when taking up the drive on a Volvo Estate that we towed horses with - it was an engine mount that had come unbonded. It looked normal when at rest of course. I would check the engine as well as the gearbox & TB mounts.

I can't think of anything inside the TB that would thump only when taking up the drive. The weakest component (the one I change most frequently) is the Centre Diff Planet Carrier that can split or shatter when overworked with off-roading. That would be obvious all the time.

You could try setting a smart phone to 'video record' and set it under the car. If you get thumping when taking up the drive it should show up on the recording. You may have to do this a few time looking in different directions to catch it.

A few ideas for you. An interesting problem this !

Bob.
 
Are you leaking oil from the front diff input shaft and/or the TB front output shaft ?? A worn-out bearing in either place would cause vibration. You say that the propshaft UJs are fine, they can be a source of vibration when worn.

Loose propshaft bolts would also cause vibration.

The Centre Diff Lock sleeve is a substantial lump of steel, I think it will survive any abuse, let alone normal running on one propshaft.

Thumping when taking up the drive (manual clutch) could be the exhaust system hitting somewhere - have you checked this ?

I had 'thumping' when taking up the drive on a Volvo Estate that we towed horses with - it was an engine mount that had come unbonded. It looked normal when at rest of course. I would check the engine as well as the gearbox & TB mounts.

I can't think of anything inside the TB that would thump only when taking up the drive. The weakest component (the one I change most frequently) is the Centre Diff Planet Carrier that can split or shatter when overworked with off-roading. That would be obvious all the time.

You could try setting a smart phone to 'video record' and set it under the car. If you get thumping when taking up the drive it should show up on the recording. You may have to do this a few time looking in different directions to catch it.

A few ideas for you. An interesting problem this !

Bob.
No leaks from the TB and bearings feel ok, propshaft UJs seem fine also, and the bolts were tight when I removed the shaft.

I took it for a decent run over the weekend and it was like a new truck. It seems that removing the front shaft has done away with the thumping noise. I bumped into a mate Sunday afternoon who knows a wee bit about transmissions, and he suggested that the thumping could be a backlash on the front diff, so I jacked her up yesterday to check it out. The front diff flange has a free play of around 15deg or roughly 3 minutes, and the TB output shaft has a free play of around 5deg or 1 minute roughly. So from this I'm thinking that my front diff is the main root of the problem, but the question is, does the slight free play in the TB output shaft indicate a problem in the TB?
 
The 5 degree play in the front output shaft is just caused by slight slackness in the Hi-Vo chain. even new chains aren't bowstring tight !

5 degrees sounds minimal, I wouldn't worry about it.

Bob.
 
The 5 degree play in the front output shaft is just caused by slight slackness in the Hi-Vo chain. even new chains aren't bowstring tight !

5 degrees sounds minimal, I wouldn't worry about it.

Bob.
Thanks Bob, I'm going to service the TB and leave it in place. My focus is now switching to finding a front diff. I believe the early autos and all the manuals came out with a 4:1, so l think the search will be relatively easy.
 
Hi Bob i saw the tread I have some issues with my gx95 diesel automatic. I was stuck yesterday an put it in low range with of course center diff locked crawled a bit with a little foot on the brake and the gas at the same, time no odd noises all is good. Now she won't unlock the center diff drives fine go easily in low range an out again og won't unlock, any clues? Best regards Simon Olesen BTW I have been working with toyota 15 years not much on lc 90 these are too old to get to authorized toyota shops.
 
Simon,
The low ratio selector is direct acting - the transfer lever moves the dog that engages low. The centre diff lock, on the other hand, works via a sprung selector. This allows the diff lock to be engaged at speed (up to 50mph I believe the book says) but it won't engage until everything lines up - it helps if you back the throttle off a touch!
If you haven't used this feature for a while or if the oil hasn't been changed and is contaminated the action may be stiff.
Try driving backwards and forwards a few times to get it to free-up.
The more the diff lock and low ratio are selected the better they will work.
There is a feint chance that the detector switch is faulty but it should be obvious if the diff lock is actually engaged (tyre squeal and rolling resistance when cornering).
Bob.
 
Simon,
The low ratio selector is direct acting - the transfer lever moves the dog that engages low. The centre diff lock, on the other hand, works via a sprung selector. This allows the diff lock to be engaged at speed (up to 50mph I believe the book says) but it won't engage until everything lines up - it helps if you back the throttle off a touch!
If you haven't used this feature for a while or if the oil hasn't been changed and is contaminated the action may be stiff.
Try driving backwards and forwards a few times to get it to free-up.
The more the diff lock and low ratio are selected the better they will work.
There is a feint chance that the detector switch is faulty but it should be obvious if the diff lock is actually engaged (tyre squeal and rolling resistance when cornering).
Bob.
Thanks for quick response it is locked feels funny backing up while turning, I would say I have tried back and forward a dusin times, could anything been broken? I was thinking of removing the transfer case and taking it apart on the table, do you think it would be overkill?
 
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