Gearbox/Transfer Box - Confused or Mis-lead

Would someone please Confirm/Clarify......I have now changed the Gearbox oil and filter several times on my P38, I was led to believe that you could not change ALL of the oil in the gerbox as several litres were left in the transfer box and the suggestion was to run the car for a couple of hundered miles and then do it again.....

However, while randomly lying under the car the other day, I noticed a drain plug and filler plug on the back of the transfer box.

So...........Are the gearbox and Transfer box linked? or are they two seperate units? If I remove the drain plug on the transfer box, will I lose the gear box oil? Don't want to do this as I have just changed the gear box oil, but I have NEVER replaced the transfer box oil I have had the car nearly 3 years and have put 65,000 miles on it, I have no idea when it was last changed and the car is now on 180k......

Advice please

transfer box and gear box are totally seperate ,you cant change all the oil in a auto box as torque convertor cant be drained

You indeed cannot drain the entire gearbox oil out, if you want to do a better change drain and refill then run for a few days and drain and fill again. The transfer box is separate from the gearbox and must be drained and refill independently.

They are seperate units transfer box runs off shaft from rear of gearbox . The gearbox ( if it's an auto ) doesn't drain fully due to torque converter , but you can drain and refill transfer box without affecting main gearbox .

scotchgit said:

They are seperate units transfer box runs off shaft from rear of gearbox . The gearbox ( if it's an auto ) doesn't drain fully due to torque converter , but you can drain and refill transfer box without affecting main gearbox .

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Yes two boxes one for gears and one for low box and diff lock

wammers said:

You indeed cannot drain the entire gearbox oil out, if you want to do a better change drain and refill then run for a few days and drain and fill again. The transfer box is separate from the gearbox and must be drained and refill independently.

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Thanks Wammers, I just went back to my original post regarding changing the gearbox oil, and it was you who did state that it was the Torque converter, So i have obviously mis-read (or at the time probably mis-understood) the difference....

How often should the transfer box oil be replaced? same time as the gear box oil??

Thanks...

hoarec said:

Thanks Wammers, I just went back to my original post regarding changing the gearbox oil, and it was you who did state that it was the Torque converter, So i have obviously mis-read (or at the time probably mis-understood) the difference....

How often should the transfer box oil be replaced? same time as the gear box oil??

Thanks...

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Every 24,000 miles. Same as gearbox oil.