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Fitting Sprite gearbox


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I know this subject has been well covered but I have searched the posts and cannot quite find the answer I need. If anyone can direct me to some relevent information, I would be very grateful.

I have a 1971 non-overdrive car and a Dolomite Sprint box with J type overdrive. I also have a tr6 input shaft and layshaft gear.

Can anyone let me know the procedure for modifications to get this box to fit and what other parts I will need.

From reading other posts, I am aware of the need to fit a modified rear mounting.

Edited by Quark
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I know this subject has been well covered but I have searched the posts and cannot quite find the answer I need. If anyone can direct me to some relevent information, I would be very grateful.

I have a 1971 non-overdrive car and a Dolamite Sprint box with J type overdrive. I also have a tr6 input shaft and layshaft gear.

Can anyone let me know the procedure for modifications to get this box to fit and what other parts I will need.

From reading other posts, I am aware of the need to fit a modified rear mounting.

 

you need to fit the tr input shaft and matching layshaft gear.[constant pinion gear]to the sprint box

make sure the input shaft you have is metric to match the sprint mainshaft.

the rear flange will need changing.or altering.

the speedo drives gears in the back of the od drive will req changing, remove rear of od.

or get the speedo recalibrated,

make up or buy a mounting.

you should be able to strip and swap the bits over in 1 day.

richard

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you need to fit the tr input shaft and matching layshaft gear.[constant pinion gear]to the sprint box

make sure the input shaft you have is metric to match the sprint mainshaft.

the rear flange will need changing.or altering.

the speedo drives gears in the back of the od drive will req changing, remove rear of od.

or get the speedo recalibrated,

make up or buy a mounting.

you should be able to strip and swap the bits over in 1 day.

richard

 

How can I identify whether I have the correct input shaft? There do not appear to be any identification marks on it.

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How can I identify whether I have the correct input shaft? There do not appear to be any identification marks on it.

i dont know what the measurments are.

you will have to measure the hole in the input shaft [where the bearing fits].

and see if its the same as the sprint box. if the tr one is bigger its imperial,

and will req a bush.moss sell them.

dont try and pull the input shaft out of the sprint box,it wont come out untill the

laygear has been droped into the bottom of the gbox.

if i were you i would strip the sprint box.have a good poke around and see how it all fits toghether.

check the 2/3rd gear for play[there will be some].but you dont want tons.

check the rear of the lay shaft/gear for wear.

dont be too concerned about the gaps between the baulk rings. push them onto the gear and feel how well they grip.they should stick if you push them on hard.

then order any bits you might need.

ors sheffield is best, get a new layshaft and ask them to test it for hardness.

the sprint box is better than earlier boxs it has steel bushes instead of bronze.

the gbox in your 71 tr6 should be metric unless someones been in there already.

+ you will need the nose from the tr box.

id better stop now, im rambling on a bit... richard

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i dont know what the measurments are.

you will have to measure the hole in the input shaft [where the bearing fits].

and see if its the same as the sprint box. if the tr one is bigger its imperial,

and will req a bush.moss sell them.

dont try and pull the input shaft out of the sprint box,it wont come out untill the

laygear has been droped into the bottom of the gbox.

if i were you i would strip the sprint box.have a good poke around and see how it all fits toghether.

check the 2/3rd gear for play[there will be some].but you dont want tons.

check the rear of the lay shaft/gear for wear.

dont be too concerned about the gaps between the baulk rings. push them onto the gear and feel how well they grip.they should stick if you push them on hard.

then order any bits you might need.

ors sheffield is best, get a new layshaft and ask them to test it for hardness.

the sprint box is better than earlier boxs it has steel bushes instead of bronze.

the gbox in your 71 tr6 should be metric unless someones been in there already.

+ you will need the nose from the tr box.

id better stop now, im rambling on a bit... richard

 

Sounds like a more complicated operation than I hoped. I am guessing that fitting the J type overdrive to my A type non-overdrive box would not be any easier?

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Sounds like a more complicated operation than I hoped. I am guessing that fitting the J type overdrive to my A type non-overdrive box would not be any easier?

 

no its not as bad as it sounds pull the sprint box in bits and have look at it.

and no way will the j odrive fit on the back of a non odrive box .it will if you change the mainshaft.

richard

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no its not as bad as it sounds pull the sprint box in bits and have look at it.

and no way will the j odrive fit on the back of a non odrive box .it will if you change the mainshaft.

richard

 

I have just read some advice on fitting a J type overdrive unit including changing the mainshaft (which appeals because I know my current box is good) and it would appear that I need £850 worth of bits and would be better off changing the whole gearbox! I am really scared now, I thought I had found an inexpensive solution?

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I have just read some advice on fitting a J type overdrive unit including changing the mainshaft (which appeals because I know my current box is good) and it would appear that I need £850 worth of bits and would be better off changing the whole gearbox! I am really scared now, I thought I had found an inexpensive solution?

 

i dont know where youve got £850 from i would say £125 top

new rear drive flange £45

layshaft £25 full compliment rear laygear bearing £15

speedo gears £40

gaskets oil seals£25

the main bearings will be ok.if not use the tr ones.new ones not so good.

your tr6 box wont be as good as the sprint remember it will have bronze bushes,

where as the sprint has steel.plus it will have a higher first gear.[close ratio]

again id say pull the sprint gearbox in bits and get to know how it fits toghether.

cost nothing.

richard

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I have just read some advice on fitting a J type overdrive unit including changing the mainshaft (which appeals because I know my current box is good) and it would appear that I need £850 worth of bits and would be better off changing the whole gearbox! I am really scared now, I thought I had found an inexpensive solution?

 

OK, I'll have a good read of Haynes and give it a go. If anyone knows any good tips and pitfalls to avoid, I would be pleased to hear from you.

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OK, I'll have a good read of Haynes and give it a go. If anyone knows any good tips and pitfalls to avoid, I would be pleased to hear from you.

 

Williams has quite a lot to say about gearboxes. For example, p54 of his How to Improve book.

 

Ivor

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Hi Quark,

I did exactly what you are proposing to do, in my case I adapted a 1974 Dolomite Sprint J-Type overdrive gearbox to fit in my TR6.

Richard has summed it up really well, it may sound a daunting task, but it's pretty simple providing you take it slowly.

The only advice I can give is to take lots of photos as you're doing it. I kept costs down by only replacing what needed to be changed ( I didn't have a job at the time) and refer to the manual and reference books. I found the Practical Classics Triumph TR6 Restoration book invaluable for reference photographs (ISBN 1 873098 27 8).

I actually used the input shaft and laygear from a Triumph 2500 that I had been given free because I wanted to use the 2500 clutch release mechanism and bearing that doesn't suffer from all the well known TR problems. Because the 2500 release bearing presses further towards the ends of the clutch pressure plate 'fingers' due to its slightly smaller diameter, you need to apply less force on the clutch release bearing, but longer movement. This has the effect of longer life of the bearing and less stress on the tapered clutch fork bolt. (You dont see many posts on the Triumph 2000/2500 Register forum about clutch release mechanism problems).

Good luck with it.

Chris

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