More gearbox trouble on a diesel Rover

Well, I seem to have jinxed another one. This time the manual box on my 620D has started making really loud noises whenever the car is being driven
(not so bad when coasting though), and there is very little drive when in reverse gear and it judders a lot. Suffice to say I think it's got problems...
So I read the Rover overhaul manual for this gearbox (PG1) and it says that the same gearbox is fitted to a number of petrol and diesel Rovers throughout the last decade or so.
I couldn't find a 620D gearbox but I did find a 220D one on eBay (same engine, smaller car) and from the photo it looked the same as mine. However it wasn't until I got it home that I spotted the difference - mine had a cut-out and bolt holes for a hydraulic slave cylinder whereas the 'new' one has an arm for cable operation. :-(
I haven't removed the original gearbox from the car yet, but I'm planning on opening them both up and transferring the innards. From the symptoms mine has I would say it's likely to be collapsed bearings on one of the shafts or differential (especially as there's an almighty oil leak out of one of the driveshaft seals). I just hope that they are more similar inside than out!
Anybody done this before? Obviously I won't know exactly what's died until I split the original 'box apart, but a google search throws up a few mentions of diff bearings so I'm hoping that that's all it'll be (presumably I can just swap the diff complete from the other g/box, maybe changing the final drive ring gear if needed?)
Scrapyards near me want 150 for a s/hand gearbox with 30 day warranty - being as they only pay a tenner on average for cars they get in (and it's about 200 to have mine reconditioned) I thought it would be worth a shot at having a go myself - just wish I'd noticed the clutch release mechanism before I'd bought it!!!
Darren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"> I haven't removed the original gearbox from the car yet, but I'm planning on

Well I've split open the replacement gearbox I bought - all looks straight-forward enough inside and the bearings seem fine; except the inner one of the two on the gearbox casing end of the output shaft which feels loose. Is this normal or should I worry? I'd have thought it should feel just like the other bearings but with the two being mounted next to each other I wasn't so sure.
How difficult is it to replace these bearings WITHOUT any special tools or pullers? I know that I'll need to un-stake and remove the nut on the end of the output shaft first, and pull off the (good) outer bearing, but how?
Looks like I'm going to be having a 'fun' weekend...
Darren
P.S.
Rover have an irritating habit of using RTV (whatever that is) silicone sealant instead of proper gaskets - what can I use in place of that for sealing the gearbox seam when I put it back together? Would ordinary silicone work, or maybe even blue Hermatite???
Darren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I've been working on the car today and managed to remove everything around the gearbox but not the 'box itself (will try that tomorrow if it's not raining). However, I have now found at least one problem with the gearbox - as I pulled out the LH driveshaft a rather worn oil seal and loads of little steel balls fell out!
I can see that the diff bearing is knackered but I hope that that's all there is wrong with the gearbox because it's the higher torque version of the one I got from eBay (which has a different release arm anyway) and the shafts aren't interchangeable between the two types. :-(
So... I'm hoping that I can just replace the diff on it's own (complete with bearings) and if needed, the final drive ring gear. What worries me is if the speedo drive gear is different between the two diffs (the 600 uses 15" wheels whereas I think the new shape 200 still uses 14"). Unfortunately you have to pull the bearing off to replace the speedo drive and I don't have any type of bearing pullers to do that with.
Maybe I've taken onboard more than I can handle? Still, even if I can't get fix the gearbox myself I'll have had the experience of taking yet another apart...
Darren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well I've now removed the gearbox and opened it up. Unfortunately the bearing spread itself all over the insides of the casing and has managed to wreck the teeth of the diff ring gear and the final drive pinion on the output shaft (the only one which isn't replaceable!). Of course, there is also 'swarf' everywhere inside the casing and it'd be a pain to clean it all out of the other bearings effectively.
So... my gearbox is essentially scrap. However I have since found out that the one I got from eBay *is* the uprated version and I only need to swap the release arm over (very quick and doesn't need the gearbox dismantling), so at least I have one to put back on.
I still have the problem that I don't know if the speedo drive is the same gearing (I think it is but if not then I'll also use the new speed sender and forego the speed-sensitive PAS function), and I think that the gearing itself is probably slightly higher - but I don't imagine that being too much of a problem.
Darren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.