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Hi guys
I have been thinking one this for a while now, I have had my Prado for about 10 years and this has always given me the sh!ts, the inability to engage low range without the CDL (centre diff lock) being locked.
There have been a number of threads on here over the years on this topic and several people have expressed an interest in changing this "design feature", but it has always been resigned to the too hard basket.
https://www.pradopoint.com.au/forum/...d-in-low-range
https://www.pradopoint.com.au/forum/...range-unlocked
I fail to see why Mr Toyota/Aisan, limited the VF4B transfers from being able to be low range unlocked. It’s not that the manual box 5/6 speeds are limited this way, possibly due to the smoother torque output of the autos, if the car has VSC/traction control then they have the VF4BM which can be driven in low unlocked. They are the same box internally apart from the CDL actuation method. Even the owners manual advises to only lock the CDL in low range when absolutely necessary - the Torsen centre diff is pretty good in that regard.
My Prado is a '05 KZJ120 GXL with the 5 speed R150F manual gearbox and VF4B manual transfer case. I tow often and do a fair amount of off road work, the 1KZ isn't a power house - first gear on the R150F is quite tall requiring some clutch slip to get going. I have had, on a number of occasions, towing up a steep hill in hilly areas on tarmac, been down to first gear - and losing speed with no more gears left. Not a good idea to engage low range on tar with the CDL engaged unless it's a straight road. Also, a steep hill-start with a fully loaded car and camper trailer in high range isn't at all kind on the clutch. It would also be to great be able to reverse my camper trailer slowly uphill at an angle on the driveway into my carport in low unlocked. I like to think I have some level of mechanical sympathy.
So, serious thought into making this mod happen. FJ Cruisers in the states came with VF2A part time transfers or VF4B/M full time transfer cases. The full time FWD manual transfer cases can be fitted with aftermarket twin sticks for not much $, to select range and CDL independently. They use a similar VF4B transfer as well though they are a top shift transfer, whereas the Prado VF4B/M are forward shift (top shift - the gear lever is in the top of the transfer whereas the forward shift have the gear lever mounted on the transfer adapter on the back of the transmission). I had no intention of butchering the interior of my car - cutting extra holes in plastic and creating dramas sealing up the rubber boot arrangement for the gear levers. So, single stick it had to be, or replace the transfer with a VF4BM and rig up an electrical system for the CDL. My transfer case is in good condition so I didn't want to spend $500-$600 on another second hand case.
I have the factory service manual and spent some time studying it to figure out if the interlocking arrangement of the shift rails for lock and range can be separated. I ordered some parts from Amayama to play with and set to work, it's not a huge job removing the transfer case on the Prado. I stripped the transfer and worked out what needed to be done. Once I had all the notes I needed, I rebuilt it and fitted it back into the car.
The main mod involves increasing the lock shift gate slot dimension so that the gear lever can be moved across to the range shift gate without moving the lock rail first into lock. Then the gear lever needs to be biased to the range rail by the spring, so that the increased free play doesn't cause the lever to float backwards and forwards slightly in the gate. This is just my personal preference and if you feel that's not needed that's up to you. This gate also needs a lug welded to the end to stop the lever moving across to dead space between the gates when in low unlocked.
There is an interlock pin between the two rails that prevents low range unless the lock rail is in the lock position. That can easily be removed, but there is also a link between the two rails, such that when low range is selected it forces the lock rail positively into the lock position. This link also has the function of preventing the lock rail rotating and limits the range rail travel in the low range position, so it couldn't be just simply removed. Some workarounds for this took some figuring out. I wanted the mod to be completely reversible, cheap and reliable. The last thing I wanted was for something to fail hundreds of km from civilisation. The range shift gate requires a stop welded to it to limit the travel of the lock rail once the circlip and interlock pin are removed. The stop contacts the transfer housing next to the rail seal. If this isn't done the rail will over travel resulting in the range hub going out of mesh and it will be very hard to get the rail back and synchro hub to realign and engage.
So parts required to complete the mod.
36315-60030 HEAD, TRANSFER GEAR SHIFT, NO.1 $8.43 x1
36316-60010 HEAD, TRANSFER GEAR SHIFT, NO.2 $6.92 x1
Big expense hey? I bought a few other things as well seeing as it was a viability exercise, spare roll pins, a rail shaft, seals, circlips etc. All up I probably spent around $100 for everything inc. freight.
You could remove the transfer and mod the shift gates for zero parts cost, but I wanted to be able to revert this back to standard operation and I didn't want the car to be off the road for an extended period. It is my daily drive.
There is labour cost (mine was free) and you may want to change seals, oil etc while the case is out. For the 10mm tool steel, I bought a cheap pry bar from supercheap for about $12 which will give you enough material to modify 10 gates. You will need a welder - I have a TIG - I used EN70 filler rod using preheat and post heat treatment, if I had the rods handy I suppose I could have used 312 stainless (good for welding dissimilar/high carbon/tool steel/heat treated metals).
Pictures to come
Edit, video added
https://youtu.be/fNvnI1MCkqY
I have been thinking one this for a while now, I have had my Prado for about 10 years and this has always given me the sh!ts, the inability to engage low range without the CDL (centre diff lock) being locked.
There have been a number of threads on here over the years on this topic and several people have expressed an interest in changing this "design feature", but it has always been resigned to the too hard basket.
https://www.pradopoint.com.au/forum/...d-in-low-range
https://www.pradopoint.com.au/forum/...range-unlocked
I fail to see why Mr Toyota/Aisan, limited the VF4B transfers from being able to be low range unlocked. It’s not that the manual box 5/6 speeds are limited this way, possibly due to the smoother torque output of the autos, if the car has VSC/traction control then they have the VF4BM which can be driven in low unlocked. They are the same box internally apart from the CDL actuation method. Even the owners manual advises to only lock the CDL in low range when absolutely necessary - the Torsen centre diff is pretty good in that regard.
My Prado is a '05 KZJ120 GXL with the 5 speed R150F manual gearbox and VF4B manual transfer case. I tow often and do a fair amount of off road work, the 1KZ isn't a power house - first gear on the R150F is quite tall requiring some clutch slip to get going. I have had, on a number of occasions, towing up a steep hill in hilly areas on tarmac, been down to first gear - and losing speed with no more gears left. Not a good idea to engage low range on tar with the CDL engaged unless it's a straight road. Also, a steep hill-start with a fully loaded car and camper trailer in high range isn't at all kind on the clutch. It would also be to great be able to reverse my camper trailer slowly uphill at an angle on the driveway into my carport in low unlocked. I like to think I have some level of mechanical sympathy.
So, serious thought into making this mod happen. FJ Cruisers in the states came with VF2A part time transfers or VF4B/M full time transfer cases. The full time FWD manual transfer cases can be fitted with aftermarket twin sticks for not much $, to select range and CDL independently. They use a similar VF4B transfer as well though they are a top shift transfer, whereas the Prado VF4B/M are forward shift (top shift - the gear lever is in the top of the transfer whereas the forward shift have the gear lever mounted on the transfer adapter on the back of the transmission). I had no intention of butchering the interior of my car - cutting extra holes in plastic and creating dramas sealing up the rubber boot arrangement for the gear levers. So, single stick it had to be, or replace the transfer with a VF4BM and rig up an electrical system for the CDL. My transfer case is in good condition so I didn't want to spend $500-$600 on another second hand case.
I have the factory service manual and spent some time studying it to figure out if the interlocking arrangement of the shift rails for lock and range can be separated. I ordered some parts from Amayama to play with and set to work, it's not a huge job removing the transfer case on the Prado. I stripped the transfer and worked out what needed to be done. Once I had all the notes I needed, I rebuilt it and fitted it back into the car.
The main mod involves increasing the lock shift gate slot dimension so that the gear lever can be moved across to the range shift gate without moving the lock rail first into lock. Then the gear lever needs to be biased to the range rail by the spring, so that the increased free play doesn't cause the lever to float backwards and forwards slightly in the gate. This is just my personal preference and if you feel that's not needed that's up to you. This gate also needs a lug welded to the end to stop the lever moving across to dead space between the gates when in low unlocked.
There is an interlock pin between the two rails that prevents low range unless the lock rail is in the lock position. That can easily be removed, but there is also a link between the two rails, such that when low range is selected it forces the lock rail positively into the lock position. This link also has the function of preventing the lock rail rotating and limits the range rail travel in the low range position, so it couldn't be just simply removed. Some workarounds for this took some figuring out. I wanted the mod to be completely reversible, cheap and reliable. The last thing I wanted was for something to fail hundreds of km from civilisation. The range shift gate requires a stop welded to it to limit the travel of the lock rail once the circlip and interlock pin are removed. The stop contacts the transfer housing next to the rail seal. If this isn't done the rail will over travel resulting in the range hub going out of mesh and it will be very hard to get the rail back and synchro hub to realign and engage.
So parts required to complete the mod.
36315-60030 HEAD, TRANSFER GEAR SHIFT, NO.1 $8.43 x1
36316-60010 HEAD, TRANSFER GEAR SHIFT, NO.2 $6.92 x1
Big expense hey? I bought a few other things as well seeing as it was a viability exercise, spare roll pins, a rail shaft, seals, circlips etc. All up I probably spent around $100 for everything inc. freight.
You could remove the transfer and mod the shift gates for zero parts cost, but I wanted to be able to revert this back to standard operation and I didn't want the car to be off the road for an extended period. It is my daily drive.
There is labour cost (mine was free) and you may want to change seals, oil etc while the case is out. For the 10mm tool steel, I bought a cheap pry bar from supercheap for about $12 which will give you enough material to modify 10 gates. You will need a welder - I have a TIG - I used EN70 filler rod using preheat and post heat treatment, if I had the rods handy I suppose I could have used 312 stainless (good for welding dissimilar/high carbon/tool steel/heat treated metals).
Pictures to come
Edit, video added
https://youtu.be/fNvnI1MCkqY
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