tiagoc Posted March 30, 2006 Share Posted March 30, 2006 I know the common solution for the problem of gears jumping out of 1st or 2nd, is to check if the synchros or the gear's teeths are worn out. But if it only seems to happen in high 1st, could it be the same problem? When in low 1st, the gearbox can hold the pressure. I didn't try to descend a *very* steep hill, yet... So I'm not sure if it would happen also in low 1st. The problem is that the gearbox+transfer were bought with a 12 month warranty (still in effect, so I don't want to open it) and the gearbox was checked several times allready by the seller, who diagnosed several worn out parts, that were replaced by brand new ones (so they say...). I'm sorry, but I don't know the names of those parts in English The seller is now saying that the problem has nothing to do with the gearbox+transfer and that they can't be responsible for the "abusive use of the vehicle, that causes the probems described". Do they consider light off-roadding with a SIII an abusive use of the vehicle? Seems like it... Anyway, the seller says that the gearbox is a suffix D, with new parts installed. Before I go to court, to ask for a refund, I'd like to know what you think of this problem and (hopefully) give me some explanation/solution for the "jumping gear". I'll add that the SIII has an overdrive installed, but it's always disengaged when the "jump" occurs (I only use it in high 4th gear). Quote Link to comment Share on other sites More sharing options...
minivin Posted March 31, 2006 Share Posted March 31, 2006 Can't remember the exact terms either at this time in the morning but it sounds to me that the angle on the teeth for the engagement dog to the 1st gear are worn, such that under the heavier torque loading of running Low-1st the teeth are under enough loading to keep them engaged, but in Hi-1st with the lower torque the forces are no longer enough to keep the teeth engaging each other. Therefore I would think that it's either of two scenarios: 1) The teeth have been machined the wrong angle for keeping them engaged 2) The teeth have moderatly worn, such that they are still engaging under load, but not under a moderate load. It's failed within the 12 month warrenty period, it needs replacing! Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted March 31, 2006 Share Posted March 31, 2006 In a suffix D box the engagement teeth in the syncro hubs are machined with a relief so that when in gear there is a ridge that would need to be ridden over to jump out of gear. These gears are refered to as ECM gears. Jumping out if both gear and syncro hub are new and the correct part, this also includes the selector rail, for a D suffix box can only be down to incorrect setting of the selector fork on the selector rail, making it so that the engagement is not far enough in, meaning that there is no ridge to ride over to jump out of gear. Quote Link to comment Share on other sites More sharing options...
tiagoc Posted March 31, 2006 Author Share Posted March 31, 2006 2) The teeth have moderatly worn, such that they are still engaging under load, but not under a moderate load. I also thought about that, but I didn't know if it would make much sense... I'm glad you also think that could explain it In a suffix D box the engagement teeth in the syncro hubs are machined with a relief so that when in gear there is a ridge that would need to be ridden over to jump out of gear. These gears are refered to as ECM gears. Jumping out if both gear and syncro hub are new and the correct part, this also includes the selector rail, for a D suffix box can only be down to incorrect setting of the selector fork on the selector rail, making it so that the engagement is not far enough in, meaning that there is no ridge to ride over to jump out of gear. looking at some pictures from the Repair Operation Manual (page 37-7), I see that the selector rail for the 1st/2nd is the one in the middle. It's the only one with 4 grooves on top, but the selector fork should be aligned with the first groove ("nearest to the front of the shaft"). What you're saying is that the selector fork could be aligned with the wrong groove? BTW, the lenght of that selector rail is the same, on gearboxes with different suffixes? How can I make sure that the correct selector rail is being used? Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted April 1, 2006 Share Posted April 1, 2006 There is only 2 options for the selector rail, suffix A, B & C and D onwards. The differences on a D on are; the front groove is wider allowing more lengthwise adjustment movement of the fork on the rail, the other is on the 3 grooves on top(1-N-2), the distance between 1/2 and N is larger on the D suffix as they need a larger depth of engagement. If the early rail has been fitted with D gears it will jump out of 1st & 2nd. If you look at page 37-20 there is some info about the setting of the 1st/2nd fork on the rail for D on boxes. Hope this helps. Quote Link to comment Share on other sites More sharing options...
tiagoc Posted April 3, 2006 Author Share Posted April 3, 2006 There is only 2 options for the selector rail, suffix A, B & C and D onwards. The differences on a D on are; the front groove is wider allowing more lengthwise adjustment movement of the fork on the rail, the other is on the 3 grooves on top(1-N-2), the distance between 1/2 and N is larger on the D suffix as they need a larger depth of engagement.If the early rail has been fitted with D gears it will jump out of 1st & 2nd. If you look at page 37-20 there is some info about the setting of the 1st/2nd fork on the rail for D on boxes. Hope this helps. Great information, Phil. Thanks a lot! I also checked the parts catalogue for a list of part numbers and references for suffix D, so that will help too (I hope). By looking at the pictures, I get the impression that it's possible to adjust the fork without taking the gearbox out. Just openning the top lid I should have access to the rail and the screw that fixes the fork in place. Is this correct? Or does the gearbox have to come out, one more time? Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted April 3, 2006 Share Posted April 3, 2006 Great information, Phil. Thanks a lot! I also checked the parts catalogue for a list of part numbers and references for suffix D, so that will help too (I hope).By looking at the pictures, I get the impression that it's possible to adjust the fork without taking the gearbox out. Just openning the top lid I should have access to the rail and the screw that fixes the fork in place. Is this correct? Or does the gearbox have to come out, one more time? Yes just take the top off in situ to get at the selectors. DONT drop the selector detent balls or plungers in the box when you take the top off. On the A, B or C selector rail the notch that the selector fork pinch bolt goes thro is only slightly bigger than the bolt but the D on rail has an extended notch that will allow more movement to the fork so the bottom of the notch is flat. Quote Link to comment Share on other sites More sharing options...
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