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| Removing gearbox front cover | Rate Topic |
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| Posted: 08-08-2025 06:10 am |
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1st Post |
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rr@porte-velo.com.au Member
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Having difficulty removing the front cover, to replace the front gearbox seal. Even though exploded drawings indicate the cover should come off easily, about 3mm movement is all I get. Any assistance appreciated! Attachment: JH Front Cover.jpg (Downloaded 51 times)
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| Posted: 08-08-2025 08:22 pm |
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2nd Post |
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vnavaret Member 
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Sorry, but it is not that easy (I am assuming we are talking 4 speed, correct?). To replace the oil seal, you need to remove the primary shaft. =:-( The front cover carries the oil seal and the primary shaft input bearing, which has a retaining clip (item #27) that rides inside the front cover. To get at the front seal the primary shaft must come out of the casing along with the front cover. The retaining clip then can be removed along with the primary shaft and bearing, and only then the seal can be replaced. So you are looking at removing the top cover, the tail shaft housing, gear clusters, etc. Look at the bright side: It's a good excuse to go through the entire gearbox to replace those worn synchros and shift forks. OK, maybe that is a stretch if your only complaint is an oil leak. Time for a five speed conversion? Vance Attachment: Screenshot 2025-08-08 121408.jpg (Downloaded 44 times) Last edited on 08-08-2025 08:23 pm by vnavaret |
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| Posted: 08-10-2025 08:03 am |
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3rd Post |
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rr@porte-velo.com.au Member
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And just when I was beginning to believe in the tooth fairy again....! Thanks Vance for the clarification - I'd overlooked the front retaining clip. It's nearly all apart, except that 1st gear doesn't simply slide off the main shaft as the shaft is being withdrawn, as some good reports indicate it should. In fact 1st gear refuses to go anywhere, ant it's not easy to restrain it while tapping the shaft. Life really wasn't meant to be easy......
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| Posted: 08-11-2025 02:02 pm |
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4th Post |
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rr@porte-velo.com.au Member
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Update, Vance. By placing two steel flats between the front of the casing and the back of the 1st gear cog, then applying some heat, a brass hammer drifted the shaft through the gear. One gearbox in pieces! But in hindsight, I reckoned the mainshaft didn't need to be removed - the layshaft just had to be lowered. I had another 4-speed, so I attacked it. I used a 19mm diameter timber dowel, 167mm long, as the dummy shaft for the layshaft. It was a loose running fit through the casing. 167mm was the distance between the two thrust washers, 52 and 53. Using a 3mm screw in one end of the dowel, set off-centre by about 5mm, I drifted the layshaft out so the dowel occupied the space between the thrust washers. Then another offset screw went into the dowel at the other end, and the layshaft dropped down by about 10mm onto the screws, taking the rollers and abutment rings, 51, with it. Everything was contained, hanging on the screws, and free of the primary. Pulled the cover and primary out, replaced the seal, and refitted the primary into the cover. Refitting the assembly was dead simple - once the rollers and collar of the primary were greased up, the cover assembly was bolted in place. Then by tipping the the box upside down, the layshaft just fell back into place. The layshaft itself took a minute or so to fit, to get the thrust washers in line, and with a bit of heat on the rear of the casting, the shaft just slid in. It was really satisfying that it worked, and it saved several hours (and a lot of angst!) in the process. Bob
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| Posted: 08-11-2025 05:09 pm |
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5th Post |
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vnavaret Member
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Excellent! You are a true steely-eyed British car man! Vance P.S. When I get in these situations, I tend to start spouting anatomically unlikely combinations of the part and the engineer who designed it. I am so going to hell for the naughty things that I have said. =:-( Last edited on 08-11-2025 05:10 pm by vnavaret |
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| Posted: 08-11-2025 10:29 pm |
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6th Post |
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rr@porte-velo.com.au Member
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Hahaha ...steely-eyed British car man - yes, but clearly a glutton for punishment! And I too, often wonder about the questionable lineage of some of their engineers. Still, we colonials mustn't grumble. Bob
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| Posted: 11-29-2025 04:08 pm |
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7th Post |
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fenflame Member
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There has been very few projects in the last 40 years I've been working on British cars where something was just best left to someone who has done it many times. This was actually one of those jobs. I felt the risk of something going pear shaped on me seemed higher than I was willing to risk. I ended up stripping it down to the bare gearbox and sending that off to Delta Motorsports. A trip from NH to AZ via Fedex. Mike replaced both front and back seals, inspected the entire box, paying attention to all potential wear items, gears, bearings and synchros and he gave it a clean bill of health confirming that the mileage on my car and the wear in the box were aligned. He shipped it back to me a couple of weeks later with some bottles of Redline MTL. The cost was very reasonable indeed. That was two years ago. Its been great. No leaks and super smooth shifting. I love working on every aspect of my cars and sure I would have been able to figure this out, but as an Engineer myself, I knew there were times you hand off to someone who is more experienced in something very particular. This was one of them. No regrets. Maybe I've just got soft over the years. However, congrats on figuring it out. The process to change that one seal is absolutely insane. Last edited on 11-29-2025 04:16 pm by fenflame |
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| Posted: 12-04-2025 05:45 am |
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8th Post |
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rr@porte-velo.com.au Member
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There's always another way... Attachment: Shaun.jpg (Downloaded 4 times)
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