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Gear Box Seal

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Hello all,


I currently have the gearbox out of the car, a 71B. The gearbox has been fine with no issues apart from the rear seal has been leaking allowing transmission oil to be spun around from the drive shaft. Firstly where is the best place to buy one locally, I see Motorsport Auto has them in the US but suspect these will be only for 4 speed gearboxes? And secondly, what is involved in replacing the rear seal, is it easily done, or will the gearbox need to be pulled apart? As the gearbox is otherwise fine not looking to have a rebuild done ATM.



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Places like Datsport, Stewart Wilkins Motorsport will have them, probably get them at most spares places (Repco, etc). They are common across a large number of cars fitted with 71B boxes (pretty much most Datsuns with L-series engines from the 70's and 80's) Most bearing shops will have them as well, whether they will have a listing to know what bearing is required is another question - bearing shops will refer to them by outer diameter, inner diameter and thickness rather than what car they fit.


To replace, just poke a big-ish screwdriver in behind the "lip" of the old seal and lever it out (being careful not to scratch the housing it presses into). Check that there is no groove or other damage on the tailshaft input. Clean the area. Run a smear of oil on the sealing part of the seal (the "lip" that the tailshaft yoke runs in) Then just push the new seal in, being careful not to let it "twist" or "cock" in the housing - try to keep it straight as you tap it in place with a hammer. If you have a large socket or similar (or even a bit of wood with a hole in it), use that as a "drift" on the outer edge of the new seal to drive it in evenly, otherwise tap it in carefully all around the edge, a very small amount at a time.


EDIT: Here he is http://www.swmotorsport.com.au/product_info.php?cPath=16_71&products_id=1145


Judging by that link, the 71C boxes probably have the same seal (as it mentions it fits a 200SX 5 speed)

Edited by 1600dave

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I'd check for play in the tail shaft yoke. If there is much play, I'd recommend replacing the extension housing bush, otherwise you might have another leaky seal sooner rather than later.





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Over time (30+ years of use) the smooth metal sleeve of the slip yoke that goes into the back of the box, can develop "wear" grooves, very slight, these can sometimes be just enough to allow a bit of weepage, and combined with an old seal lip, which adds to the weep.


If on install it still weeps, you may need the outer diam of the yoke shaft sleeved, if badly grooved, or if lightly, ( run your thumb nail along it) i slight touch on a lathe, and a fine polish finish may fix.

Otherwise, another front yoke/shaft assy will be needed.


As the diff (assuming a Z) is fixed, the tailshaft does not move fore/aft like cart axle sprung cars, hence the fine wear groove!

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