LT77 5 Speed Overhaul

Lovel

Lovel

Member
Spurred on by another thread I finally got going and have begun renovating my gearbox, however upon disassembly I noted that there is quite a bit of wear on the tips of the 1st/2nd selector fork. These selectors seems to be hard to come by, but I have spotted one brand new but it does not come with the shaft, I believe they were sold as an assembly.

1. Would anyone have any experience/recommendations on how to (or don’t bother) remove either of these two pins from the selector shaft in order to fit a new selector?
2. Any thoughts on building up the existing fork at the tip where it contacts the synchro ring, I would imagine that these are cast bronze and would have similar melting point to brazing and therefore impossible to add material to the face?
3.Would any other Landrover LT77 selectors fit such as FTC1490 looks very similar (it’s cheaper too) and perhaps with a bit of fettling would fit?

Round Pin located in 5th gear casing looks to be the easier to replace. Is it tapered?




 
I have heard that this type of selector wear can be caused by drivers keeping a hand on the gearlever and loading the selector against the synchro continuously....Cant help with your query unfortunately. Was there a symptom of this wear evident in using the box? What prompted the overhaul ?
 
jp928 said:
I have heard that this type of selector wear can be caused by drivers keeping a hand on the gearlever and loading the selector against the synchro continuously....Cant help with your query unfortunately. Was there a symptom of this wear evident in using the box? What prompted the overhaul ?
Click to expand...

Unfortunately I don’t know the history of the box, it came with my car when I purchased it 10 years ago. I could not fit the box without an inspection and after seeing the seals were perished I had to open it up. Additionally when you apply leverage radially at the input shaft there appeared to be some play that I did not like, however all the taper bearings were in good shape and all else I think it just the design that will always give radial play unless supported at the Bush in the crankshaft . It‘s just the selector fork on 1st/2nd is bugging me as I don’t want to put it all back and then find an issue. I am currently renewing all the bearings as a matter of course. i’m a bit concerned about the radial play on the input shaft when it comes to coupling up to the engine as I will try and avoid any radial loading on the shaft as much as possible.
 
I have a TR8 box ready to go into mine sometime, and , FWIW, the input shaft has pretty much zero discernible sideplay, same for the output shaft. There is some sealer gue on the centre plate gaskets, so I think its been opened in the past. Since the the oil pump checks out ok I plan to stuff it in and cross my fingers. I think you are wise to go through yours all things considered.
 
Change of tact. I’m going to try building up that worn area with silver solder to see if I can build it up which melts at a lower temp than the brass/alloy fork, and then file into shape.
 
If that doesn't work maybe you could machine off the worn part of the selector altogether, then drill through the selector, and then make and fit brass selector pads like the ones fitted in the P6 manual boxes.
 
Well I tried with silver solder and here are the results after a little dressing off. The material didn’t feel too soft to file and was comparable to the hardness of the bronze fork itself. I used rods with 30% Content. Certainly an improvement, hopefully lasts a while. Compare the before and after photos in my first post.
 
Looks pretty good to me. If you can get them to fit with the same clearances as the undamaged fork you might get away with it. Depends a bit on what caused the wear, and how many miles it took to produce it, compared with the miles you are going to do from here on. Interested in how much you needed special equipment to dismantle - extractors, pressing etc. Re shims for the shaft bearings - I asked Ashcrofts about shims for LT77, and they said they dont do them anymore.
 
jp928 said:
Re shims for the shaft bearings - I asked Ashcrofts about shims for LT77, and they said they dont do them anymore.
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I know someone who had a load of those, so when I get a minute I'll shoot him an email and see if he still has them.
 
Thanks Harvey, that could help quite a few - at least knowing sizes and thicknesses.
 
Lovel said:
:thumb:I could be looking for some too, just about to start shimming up.
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I emailed him yesterday, and they have all been sold. A random person walked past his workshop as everything was being sold off or disposed of and bought the lot.
 
Lovel said:
1. Would anyone have any experience/recommendations on how to (or don’t bother) remove either of these two pins from the selector shaft in order to fit a new selector?
2. Any thoughts on building up the existing fork at the tip where it contacts the synchro ring, I would imagine that these are cast bronze and would have similar melting point to brazing and therefore impossible to add material to the face?
3.Would any other Landrover LT77 selectors fit such as FTC1490 looks very similar (it’s cheaper too) and perhaps with a bit of fettling would fit?
Click to expand...
The pins will be interference fit, wooden or nylon block, pin punch a bit smaller than the hole, a buggering stick and some carefully calibrated thumping should suffice.
The Land Rover parts should be the same, the major differences are input/output shafts and maybe ratios.
 
unstable load said:
The pins will be interference fit, wooden or nylon block, pin punch a bit smaller than the hole, a buggering stick and some carefully calibrated thumping should suffice.
The Land Rover parts should be the same, the major differences are input/output shafts and maybe ratios.
Click to expand...

I got concerned I would damage the selector rod so I opted to build up the missing area with silver solder which seems to have turned out ok.
 
harveyp6 said:
I emailed him yesterday, and they have all been sold. A random person walked past his workshop as everything was being sold off or disposed of and bought the lot.
Click to expand...

That’s a pity about the shims, but thank you for enquiring about them.

So I need some shims after checking with the dial gauge. The shims currently fitted in the cavity do not seem to be the correct OD or ID, this means they have a relatively small contact point on the outer bearing race and could result in slight compression of the shim altering the pre-load or end float. Initially I wasn’t going to change the bearings as they all looked and felt good, however upon further inspection I found an inner race was pretty well gone possibly due to not enough pre-load over time.



Method used to remove the inner roller bearing outer race which is difficult to get out without the right puller. A run of weld about 2/3 the circumference, a thump on the bench and the outer race fell out easily.
 
Very interested in how you solve the shim issue. I have an indicator that could check the layshaft, but the mainshaft might need something specially constructed. In my 50+ years playing with cars Rover is the only maker I have found that specifies an end float for front hub tapered rollers - 3-5 thou. They went to some lengths with P3 and P4 to make it easy to obtain with the 52 step nut&washer on them. Maybe I havent worked on enough other makes..?
 
jp928 said:
Very interested in how you solve the shim issue. I have an indicator that could check the layshaft, but the mainshaft might need something specially constructed. In my 50+ years playing with cars Rover is the only maker I have found that specifies an end float for front hub tapered rollers - 3-5 thou. They went to some lengths with P3 and P4 to make it easy to obtain with the 52 step nut&washer on them. Maybe I havent worked on enough other makes..?
Click to expand...

Same for me, I’m currently also working on a Imp box with taper rollers on the input and that requires a pre-load reading too which you achieve by shimming and wrapping a long piece of string on the circumference one particular cog, attaching a spring balance and taking a reading until a certain reading on the spring balance is achieved. Perhaps it has something to do with heat expansion, but being cast iron I would have thought less of an issue. My Imp box is an all alloy material and would probably expand or contract more, hence I’m confused about the specs given by Rover TBH.

I have compared later Landrover LT77 specs and they slightly differ, compared to Rovers, however both still have end float on the mainshaft with Rovers tolerance slightly wider. I’m aiming for .001” end float here, but the shims are not available and actually jump in size too much for me, so I will shim with proper shim steel to get it bang on at .001“ end float (Landrover) for the mainshaft and +.002” (Rover) for the lay shaft. Because my original shims do not seem to fit the outer bearing or housing properly I am trying to source some undersize original shims which are hopefully wider in diameter and ID, then I will add in some shim steel to make up the .005” or so to get it optimum to factory specs. I can imagine that after a years or two running I may need to take the box out and check again as there may be some settling in to consider, and as you can see that little roller bearing on the mainshaft gets a hard life.

If the step gap in shim sizes are anything to go by I could envisage a few of the boxes coming out the factory missing the tolerance target.
 
Here’s how I worked out the shimming from the other face of the gearbox with the front plate bolted up fully. Gently on the tyre levers.

Layshaft clock set to zero and lifted up to show .005” or so. Rotate the gear between readings to settle in, and repeated many times.




Mainshaft zeroed and tyre lever used to take up clearance Note the use of a jubilee clip to hold the gear wheel on the mainshaft to measure the current end float.

 
I found these in the link below are a perfect fit for the mainshaft and with different thicknesses will get you do down to exactly the clearance you desire for the mainshaft having a wide contact area with the outer race much better than the originals that I found fitted in the box which were able to rattle about in the recess and had some deformation due to small contact area on outer race. For the layshaft shim a little fettling on the OD is required which I did on the lathe as the shim what relatively thick but if thin enough could be cut with scissors or tin snips. All explained in the photos below hopefully.

After much reading and deliberating over Landrover documents I have made mine:
.001” preload layshaft
.000” on the mainshaft

1.5mm THICK SHIM WASHERS HIGH QUALITY STEEL DIN 988 ALL SIZES | eBay

PS, I found them slightly below the thickness they quote on the eBay ad, doesn’t really matter at the end of the day though as long as you fill the gap.


 
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