2007 Mercedes benz actros with semi trailer... SWAP?

Condition:	Used
For Sale by:	Private Seller
Manufacturer:	Mercedes-benz
Type of Title:	Clear (most titles)
Model:	Actros
Price:	AU $56,000.00
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My 2007 Actros is up for sale with 45ft flatbed trailer. have owned it for past years. It is in very good condition for its age. Genuine 610,000km. Some of previous repairs includes:

Last year (2018).
- Full rebuild of differential
- Gear cylinder.
- New exhaust.
- All new pads and rotors
2-3 years prior
- New turbo
- New clutch
- New intercooler
-Recently serviced
PTO fitted
What is wrong with it?
The 5th gear is crunching when down gearing (only at down gearing) at high speed. Requires new synchro but according to mechanic it is not worth it until it  time to replace the clutch. we just skip 5th.

Trailer:
45ft purchased at same time as truck.

What is wrong with it?
-requires correct size airbags. We had to replace airbags few years ago, but we couldn’t find same size so were replaced with little smaller.
Will consider swapping +/- with late model auto dual cab ute.

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