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+--- Thread: 1st motion shaft (/showthread.php?tid=2108)
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1st motion shaft - Simon Scott - 11-12-2018
The gearbox jammed and I have now started stripping it. Four springs and 5 ball bearings came out in the oil and another 3 have since dropped out the drain hole. There appears to be a circlip on the 1st motion shaft bearing but Woodrow doesn’t mention one, does it need to come off?
RE: 1st motion shaft - Chris KC - 11-12-2018
Simon,
I'm going to hazard a guess you are talking about a 4 speed synchro box, though this still leaves at least two versions; and the input shaft has two bearings...
I'd suggest looking at Harold Perry's account on p149 of the A7 Companion, it should tell you all you need to know.
The 'secret' is that you must drop the layshaft cluster off its shaft before you can get the top gear sets out. The input shaft should then simply drift out from inside together with its main bearing, once the front cover (and with it the smaller roller bearing) has been removed. A warm box is much easier to strip than a stone cold one.
Sounds like a selector sleeve has sailed over its detent balls and released them - indicative of too much end float somewhere.
RE: 1st motion shaft - Terrytuned - 11-12-2018
Simon the balls and springs will be from 1st/2nd syncro hub there are 6 ball/springs in the hub 3 larger balls in the selectors. When you drop
the layshaft cluster by removing the shaft from the rear the 1st motion shaft complete with bearing will come out from the front.
Heat the front of the case to assist removal.
Terry.
RE: 1st motion shaft - Simon Scott - 11-12-2018
Thanks. It’s a 3 synchro 4 speed. I’ve got the layshaft out, Woodrow does say you can use a soft faced mallet on the 3rd motion shaft to drift out the 1st motion shaft bearing maybe I just need to warm it up and hit it harder. And get a copy of the companion.
RE: 1st motion shaft - Dave Mann - 11-12-2018
Yours is the fourth instance I've heard of this problem Simon, it happened to me descending a steep hill in Cornwall in bottom gear after which I found the transmission locked and the gear lever stuck in bottom. We wheeled the car into a car park on the front wheels where I removed the gearbox top and put the box into neutral with a borrowed crowbar, with balls and springs flying inside the box. I drained the oil and put it back in the box collecting the balls and springs and continued our honeymoon. It was a few months before I returned the balls and springs to their rightful place.
RE: 1st motion shaft - Chris KC - 11-12-2018
Happened to me in Switzerland, removed the engine and gearbox, stripped and rebuilt it before driving out over the Stelvio pass... The good news is you may well find there is no damage. Just reassemble with new balls and springs and sort out the end float.
RE: 1st motion shaft - jansens - 11-12-2018
I put mine in the oven at 100C and it all came apart pretty easily. A heat gun used carefully works too. One trick it embarrassingly took me a few minutes to discover is that to get the main shaft out you need to push some of the gears fully back on the shaft so they will clear the lip at the top of the box.
I am changing mine over to closer ratio gears and am just about to reassemble it all after having replaced the gears and all the synchro balls and springs. The hole in the tin can method for replacing the synchro balls works well.
Simon
RE: 1st motion shaft - Chris KC - 11-12-2018
(11-12-2018, 07:59 PM)jansens Wrote: I put mine in the oven at 100C and it all came apart pretty easily. A heat gun used carefully works too. One trick it embarrassingly took me a few minutes to discover is that to get the main shaft out you need to push some of the gears fully back on the shaft so they will clear the lip at the top of the box.
I am changing mine over to closer ratio gears and am just about to reassemble it all after having replaced the gears and all the synchro balls and springs. The hole in the tin can method for replacing the synchro balls works well.
Simon
+1 for a low oven, safer than local heating.
Simon, I don't know if it's any help to you but I wrote up my Swiss adventure in A7CA mag 1997D. The gist of it was to eliminate wear in the bearings, synchro cones and selector balls and springs as far as you are able then arrange for about 15 thou of end float in the shaft by shimming. Take care with the circlips on the bearings as you may need to transfer them to any new bearings you fit. The box in my Ulster continued to give good service for the next 20 years and was still going well when I opted to try a crash box last year. It was rather stiff when first rebuilt, which I attributed rightly or wrongly to failing to fit the selector rings in the same orientation.
RE: 1st motion shaft - jansens - 11-12-2018
I have a little toaster oven in the garage I use for heating up small housings or bearings and for baking paint onto small parts. I think it cost me $20 from the op shop. Very handy. The entire A7 gearbox fits easily in a domestic kitchen oven. Being a bachelor helps!
Simon
RE: 1st motion shaft - Simon Scott - 11-12-2018
I have already been told what will happen if I put it in the oven?? so need to try an alternative. With bit of luck new springs and balls and sorting the end float is all that will be required. I’ve only been 7ing a couple of years and totally in awe of the “just fixed it roadside and carried on” skills.