I have a 1996 Fiat Ducato that i had changing gears without crunching them this a synchro problems since 35Km. I had a gear oil change at 45km which showed signs of water in the oil. At 65Km the 5th gear jumped out and would not stay in. Had the gearbox removed and sent to a gearbox re-manufacture. This is what i have experienced.
The gear crunching is caused by synchro ring and the gear cone getting warn down which means they don’t bind together well and the gear gets harder and harder to change into over time. The crunching can result in wearing down the meshing teeth and eventually the gear will start jumping out. Or if the synchro and cone wear down too much they will slip which eventually they won’t mesh and you won’t be able to change into that gear.
I had all 1st- 4th synchro rings replaced at £50 each as the gears were ok. The 5th gear hub and gear mesh were warn to bad and all had to be replaced. Synchro hubs cost £150 main 5th gear £150. Sourcing 1st-4th gears and hubs is near impossible, so i was lucky that i did not need those. My 5th gear ratio was 51/31 which works out to be 51/31=1.64551 turns of the drive to make 1 turn of the output shaft( good for standard motor-home). Other ratios that can be found and many others are 53/31=1.70967(good for a towing motor-home) and 51/33= 1.54545( not good for heavy motor-homes). This is were the fun starts. The only way you will know what you have on your gearbox is open the end cover up and check, as there is no way of knowing by the reg as some vehicles were converted by motor home builders and some were after market converted. Other problems is I ran into then two gearbox styles for the 5 gear box, hydroponic or cable clutch. This makes a difference to the shaft size of the gears inside the box. My box is cable and the 5th gear shaft size is 34mm. Parts suppliers don’t have enough knowledge of their stock to distinguish the different shaft sizes for what style of box you have. So you are going to need to confirm with them what size the shafts are before purchasing.If you are lucky the gearbox manufacturer will know all this for you. You might look at changing ratio’s , but if you do that the you will need the matching pair of large drive gear and small driven gear. The small driven gears are extremely hard to get because these rarely wear out, so chances are you will only be able to get the large gear that matches your original small driven gear. It’s worth staying in conversation with your gearbox repairer as parts are varied and sometimes unavailable and so your repairer might need encouragement to continue the repair. The main reason all this happens it seems is water ingress through the breather on top of the box as many motor home screen rain water channels drain onto the gearbox. The gearbox gears are Teflon coated and the water in the box does something to wear off the coating leaving bare steal that is warn down on the gear synchro cones. So for anyone out there, get your gear oil changed and ask the garage to make something up to divert water off the top of the box. As eventual failure will happen costing just under £1.5k in labour and parts. The average price for sychro rings which you will need 5 of is £50. each gear that needs replacing is about £150. and each sychro hub is about £150. Then there is the rebuild labour costs of about £300. And then the cost of your local garage to remove and replace the box at minimum of 4hrs some say 6hrs .Oh and the clutches are another can of worms. As no doubt the clutch bearing will need replacing and they only come with a new clutch, which there are many varieties of those as well.
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By: Andrew Titcombe
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