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J type overdrive leaky or no leaky


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Advise required please on J type overdrive unit leak.  Spent £12k with a local classics specialist sorting out oil leaks from engine, gearbox, diff and overdrive.  8 month's later I notice oil under car. I  phoned specialist and they have looked at it and have said that it is the overdrive unit. After looking at schematic drawings of the unit they decide that one side of the shaft has seals and the other a plain bush and no seals and that with no seals there would always be a leak. As an engineer I find it difficult to believe that a box containing oil only has seals at one end of the shaft. The overdrive went back for refurbishment in the original work.

Am i being fobbed off by specialist or does the J type overdrive unit leak? :(

 

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hi 

mine does not leak oil on the floor, cant say its totally dry ( i havent looked )but it does not drop on the floor, thats after a year on the road.

 

Len

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Hi Bob,

which shaft are you talking about.

The three gear selector rods are contenders for the eternal leaky thing on a TR GB. t=There should be 'O' rings on each rod but they appear not to be too effective.

I have tried 'Q;seals in this area. They are like 'O' rings but with a 4 leaf clover cross section.  Some members have had success with these.

Another member fitted Lip seals to the rods and it looked a fabulous mod.

I broke into the rear cavity of the top cover and put tie wraps around the rods making any migrating oil drip off.

 

Roger

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There are only two shafts exiting the J type (excluding the gearbox selector rods as mentioned previously)

The main shaft is the obvious one, the other being the speedo drive shaft. The speedo drive has an O ring on the outside of the bearing assembly (which is just a plain drilling in the alloy housing), and an oil seal between the bearing assembly and the speedo drive shaft.

These do leak with advancing years, but I have regularly found a problem where someone has fitted a bolt that is too long on the cable retaining fork. This tends to break off the end of the casing at the bottom of the bolt hole which lets oil wick up the thread of the bolt and leak out. This is easily cured with sealant on the thread of the bolt before refitting.

One other possibility is the bolts that hold the adaptor plate to the gearbox housing. These suffer the same problem with oil wicking up the threads, again sealant does the job, and I have found loads with copper washers fitted on the bottom bolts which was not a factory fitment but stops the leaks!

Neil

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