LT77 again...

[lebochet9]

Still trying to get my 5-speed box back together. Got the input shaft endfloat just right and had a spacer ground down to the correct thickness for the laysahft. Fitted it today and somehow, in 2 weeks while the box was stiing on the bench, another 0.5mm of play has crept in to the affair, so now with the "correct" spacer in, I still have lots of play. I swear I measured the play correctly (like 30 times) and wrote down the figures for the calculation, but there is no denying the total float is now 2.5mm when it was like 1.9mm. So back to getting another spacer then...

Any theories...

But here is my real question: The Haynes manual specifies a preload on the layshaft of 0.025 to 0.05mm, wheras the Triumph repair manual (posted recently)...shows a float no the layshaft of 0.005 to 0.055mm

Which should it be???

Thanks

1980 DHC TR7-V8 (was an 8V, then a Sprint)
Back on the road after 3 years restoring...

[Beans]

My Haynes manual specifies a clearance (or endfloat) between 0.005 and 0.055 mm [8)]
Which is the same as what my BL workshop manual specifies ...

<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (not very well known yet, but back on the road)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC
http://tr7beans.blogspot.com/</i></font id="blue"></center>

[flynns tr 7]

When changing the spacers remember to torque up the bolts to the correct torgue.Grinding down the spacer is not really the best thing to do unless it was turned down on a lathe becuase grinding can vary the thickness.Also did you check the thickness of the spacer using a micrometer before you refitted the spacerand also lubricated the bearings not with greese.The overhauling of the LT77 box is not easy and should not really be attempted without the correct tools( i have done a few in the past).If you have fitted new bearings and the tolerance is within or close to the spec we are talking a cople of hundreths of a mm as long has you can turn the shafts by hand and are confident they are not excessively preloaded i would proceed bearing in mind the bearings will loosen up after a couple of hundred miles.
Flynn

[lebochet9]

Interesting Beans. The TR7 Haynes manual does indeed say the same as the Triumph repair manual. However, for some reason, in the SD1 manual that I was using, this refers to pre-load. I think I'll go with the majority....

Seems Mr Haynes changed his mind...


Flynn - I had the spacers ground in several stages on a magnetic surface grinding table at work and used a micrometer to verify the final thickness at severl points around the surface.



1980 DHC TR7-V8 (was an 8V, then a Sprint)
Back on the road after 3 years restoring...

[Workshop Help]

We set ours up on the tight side and experienced a pronounced whine or whir during acceleration thru the gears. It has taken several thousand miles for the gearbox to quiet down. It is our opinion the new bearing preload has the input shaft gear and laygear re-aquainting themselves after having been slightly separated by the bearing wear. Thus the new noise is now being quieted down as the gear teeth find a new meshing point and the new tight bearings wear in.

Or, could we be wrong?

Mildred Hargis

[samco]

When i rebuilt mine i was advised to give the shafts a good clout with a heavy object from either end to help the bearings bed in before checking the endfloat. (similar to checking the end float on a rebuilt v8 motor with the central two piece main bearing) I must confess that where I live any kind of specialist is thin in the ground and I struggled for advice. One gearbox supplier actually said that every lt 77 they rebuilt went back together with the original shims and new bearings and that the end float was never tested!! I would concur with flynns comments re end float. As long as they can turn by hand and there is some measureable endfloat I would also carry on. My endfloat was well below the specified amount but did show on the dial guage so there was some there. I suspect that when a few miles have been covered it will have bedded in nicely. The inherent design fault with the lt77 is the two facing tapered bearings at either end which give this end float. I was told by another lt77 specialist that they would give most boxes an average life of 60,000 miles before ideally they need to be re shimmed to remove excessive endfloat caused by normal wear. There is a modification that removes one of the tapered earings and replaces it with the other type (its correct name eludes me at this time) which all but removes the need to have the endfloat so precise, and makes the box then problem free. Sorry but I cant remember the name of the company and it does require the gearbox to be re machined.

If it doesn't fit you obviously need a bigger hammer.

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1980 Californian import converted to right hand drive V8. Under construction.