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[VintageLambo] Re: Urraco Blog #04: It was a quiet week...

Mike Dodge

Hi Laust, Well the story is like this! I was driving on a navigation rally and during an urban section of the run I started to hear a ticking sound from the back of the car. (almost as if it was a stone caught in a disc brake or similar sound) I stopped to check it out jacked up and spun the left rear wheel while i was doing this the ticking was eminating from the diff housing and not at the wheel! I then trailered the car home and proceded to remove the engine/gearbox for closer inspection. Once the cover was of the differential it was apparent what the problem was! I couldnt find the missing tooth but removed the crownwheel and it was sitting in a small hollow under the crownwheel hidden from view. (Incidently the backlash was about .010" and not adjustable! but wear on all faces minor and no problems with the mesh evident)At this point i was glad i trailered the car home to avaoid further dammage to the pinion which is part of the output shaft! The tooth had a large Fatigue crack that had started in the centre of the thrust face of the tooth right at the root radius. After further magnetic dye penetrant inspection (I am an aircraft engineer by trade) we discovered another tooth that was also cracking in the same area but aprox 120deg from the other one. I took the crownwheel to a well known gear repairer and manufacturer here and he repaired the broken one with totally new special welding material. He suggested leaving the other one as the crack did not apear to be very large. I decided to repair this at the same time. It was indeed cracked through aprox 30% of its thickness in an arc eminating in the same area as the first. They do crack !! My car had covered 63,000 mls from new at that time. The teeth are large and straight cut so one tooth is always under load at any one time where as helical/hypoid types often have two or more teeth carying some of the load at any one point. The rest of the gearbox had no cracking evident and is very strong! I heard that it is very similar to a Muria box? Being of the same era I would think that to be true. Someone once told me that early Muira cars had the engine oil intermixed with the gearbox oil? Cheers Mike --- In VintageLambo@yahoogroups.com, "lgpdk" wrote: > Mike Dodge, > > What do you mean by the two statements below?? > I am getting a little nervous, since I am putting significantly more > horsepower into my Jalpa and believe the transmission is the same as > yours. My Jalpa had too much crown-wheel gear noise due to sub- > optimal gear engagement and after agonizing for a long while, I have > decided to move the output shaft closer to the pinion gear. > If you still have the "lost tooth", I would be very interested in > taking a look at it to see what the problem could be (and return it > when done). > > Laust > > > From: "Mike Dodge" > Date: Tue Feb 10, 2004 1:31 am > Subject: Re: Urraco Blog #04: It was a quiet week... > > The gearbox is very well made and very strong. > > My crownwheel also failed by loosing a tooth and a second one was > cracked nearly all the way through so might be best to check that as > well. ------------------------ Yahoo! Groups Sponsor ---------------------~--> Yahoo! Autos. Everything you need to know about buying or selling a car. FREE Quotes, 360° Tours, Research, Blue Book, Compare Vehicles, Buy Used http://us.click.yahoo.com/kEZsdA/bwnGAA/YiGOAA/9jLplB/TM ---------------------------------------------------------------------~->