Hi Mike,
What can happen is, if the diff bearings are failing, the crown wheel tilts over a little bit, and the plastic drive gear for the speedo catches on the housing. When this happens, there are some lugs on the plastic gear which shear off. The plastic drive gear can then spin relative to the crown wheel, which could explain your speedo behaviour (in fact it is the classic first symptom of failing diff bearings on this gearbox - most owners weren't as observant as you, and didn't see the preceeding driveshaft seal failure!). You can check if this has happened very quickly by withdrawing the speedo drive pinion, and probing the drive gear through the hole in the diff casing. Also, see if you can "wobble" the diff by moving the driveshafts up and down while looking through the hole at the diff.
Other than this, is the car in good condition? Does the gearbox have any other faults?
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If you choose to go ahead:
If the gearbox is a four speed, they are really easy to do - budget for the price of the plastic drive gear a new speedo drive pinion, the new diff bearings, new diff seals and some gaskets. It's probably worth putting a clutch kit in, while the gearbox is out.
If it's five speed, you will probably need to hire, borrow, or buy the fifth gear removal tool - they are pressed on very tight!, and you can't split the gearbox without removing fifth gear first! Otherwise, it's a very similar job to the four speed.
Number_Cruncher
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Thanks for your reply NC.
I haven't had a look at the speedo pinion as I'm not at home but I'll have a look when I return.
Car was owned and garaged for 13 years by my grandma, and has always passed MoT with only some advisory welding done this year to the rear sills - other than that it is structurally sound. So on that count I'd sooner the devil I know.
It is a four-speed. I've been having a look at this guide www.quantums.info/gearbox.htm and am concerned by reading it that the output shaft might be knackered by it being used as the inner bearing surface, and the cost involved in replacing it (£100). Is this the same on all B4 boxes?
As I can't keep it off the road too long, and the work will have to be done at my leisure, I was thinking of getting a donor gearbox (be it 4- or 5-speed with donor linkage) and doing a straight swap after I'd rebuilt the box. If the box has 5 speeds, will the 5th not come off with a normal puller? Also, with any of the work, will I need to get a press to get the bearings off and on the shafts? Will something like this do the job cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=3200...2 ?
Sorry for all the questions, but I much appreciate the advice!
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Mike Farrow
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As you say just get a good known box, £35 for one of these from my trusted local breaker..
Go for a 5 speed same cc if possible, eg out of a 1300 car so the ratios are the same and quite rightly you need all the linkage but they used to unbolt out of the floorpan quite easily (inside under the rubber)
Escorts always dropped their diffs as n/c says, it was the law at one time and the moving speedo was the quick giveaway plus as he said lift in the shafts.
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If, like oldman, you can get a 'box for £35, it's definitely not worth going to the trouble of stripping yours down.
The gearboxes I did obviously weren't too bad, because the output shaft surfaces were OK, it was just the diff bearings that had failed.
I found great trouble removing the fifth gear, and the first one I did damaged my small Sykes puller. Thankfully, I was on the same day release course as a local Ford mechanic whom I had known for years, and we struck up a neat if unofficial arrangement, where he would allow me to use the Ford special tools, while I gave him access to Vauxhall tools. The problem with the fifth gear is that there is a thoughtfully provided groove in the upper part of the gear hub for a puller (which you can just see on the upper gear in the piccies you linked to), but it isn't deep enough to get a good grip with a standard puller. The ford puller engages with the entire circumference of this groove, rather than just where the two or three legs of a standard puller would engage.
The bit in the link about carefully grinding the inner race on the difficult side of he diff is exactly how I used to do them - if you are careful, and grind to a uniform remaining thickness, you can get the inner race to crack long before you are in danger of marking the shaft with the grinder.
If you do find the output shaft has failed, then I would imagine that the outer part of the bearing will be a real pig to get out, because it is a blind bearing, and you will struggle getting anything behind the outer race.
But, if you just fit a known good gearbox, you won't have to put yourself through this trouble!
Number_Cruncher
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But, if you just fit a known good gearbox, you won't have to put yourself through this trouble!
Too late :-$ ! I decided that not knowing the mileage of the new 'box I wasn't going to chance having the bearings let go on that, so I bought a rebuild kit from eBay. As you can see, it's taken me a month to get this far, hence why I didn't want a 'live' project on my own gearbox!
Thanks for all the help and advice so far. The story as it stands is:
'New' gearbox bought and stripped
'Box looks like it's been rebuilt before (!). 5th gear off OK but I think I'll loctite it back on
Diff bearings seemed to come off OK with bearing puller and ring gear removed
Outer race of mainshaft came out fine after I fabricated my own tool (I'll put a piccy somewhere when I've finished) and the oil slinger was removed (read destroyed)
Parts cleaned and checked ready to be put back.
One question before I proceed. What should I use on the gears and the synchros? Should I follow Haynes guide and buy the moly paste from Ford or will dad's decades old moly grease suffice? Same question goes for the detent cap seal (loctite?) and 5th gear on input shaft (lithium grease?).
Thanks again.
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Mike Farrow
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