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5 speed conversions

PostPosted: Wed Jun 30, 2010 9:09 am
by worzel
Hi all- enjoy the weather

Just a bit of a footnote really-I've had a T9 in my sprint since around 1999. With a 3.54 diff ration and std 80 aspect 13 inch tyres it gives roughly gearing of 22.7mph/1000 revs. Having heard of a clever mod (to further raise 5th gearing) that's possible only on boxes sourced from ".8 engined Capris etc the opportunity to try it out presented itself when I had to have 3rd gear attended to.

Basically you swap the complete 5th gear cluster from a 1.6/2.0 sourced box. This ups 5th from 0.82 to 0.75. In my case 5th is now approx 24.5/1000 revs. To see 50 mph at around 2000 revs is to say the least "interesting". Any concerns I had about "bogging down" were unfounded- 5th is still perfectly usable in give and take driving. No difference in noise levels though- and probably no significant difference in fuel use either. Worth doing though if anybody else has a similar T9 in their car.

On a related note- any ideas on a problem. I lifted the box to cure an annoying noise that occurred only on overrun- it's developed over the last 2 years or so. Something like a light rattle. Definitely not a whine or grinding. Gear operation seems entirely unaffected on both up and down shifts. Only 3rd is affected.

I demonstrated the fault to somebody who has worked on these boxes (and probably most other types of box as well) over the last 30 odd years. He didn't know what it was likely to be. Gave me some pointers to look for once I had it apart.

I couldn't see anything obvious so I handed the problem to him. What did he find- absolutely sod all. No odd wear patterns, no stress cracks on the teeth, no teeth chipped. All bearings etc were as new. Selector forks are as new. As I had a brand new 3rd gear he swapped it over as a last resort. I'm 100% certain it isn't related to the conversion simply because for years I've had no problems with it. The box is fairly low mileage from new

You can guess the outcome- problem still there. No worse but no better. I've done the usual checks- prop joints, gearbox mounting, checked for contact between the box and other components, engine mounts etc.

Any ideas?



Re: 5 speed conversions

PostPosted: Wed Jun 30, 2010 9:38 am
by trw99

Gearstick? If it is only when in third on the over-run, then perhaps the bottom part of the stick is lightly touching some part of the trim or body or whatever is in the area at the time! (I know nothing about the intricacies of the T9 conversion).

Such an exact science, finding rattles!


Re: 5 speed conversions

PostPosted: Thu Jul 01, 2010 9:20 am
by kstrutt11
I also have a T9 in my +2, I don't have the noise you describe.

My suggestions would be:

Does it only do it when hot or is it there all the time?
Did you change the clutch?
Have you checked propshaft U/j's.
Does it change only when you change gear, if so is it as you let the clutch up, just after clutch engagement etc?

My initial thoghts were gear rattle which is when the loose gears on the main shaft are excited by vibration answers to some of the above may give a better idea.

Re: 5 speed conversions

PostPosted: Thu Jul 01, 2010 3:57 pm
by worzel

Thanks for the ideas/suggestions.

To answer the last posting-

Noise occurs hot and cold- not more noticeable when engine/box warmed up.

Clutch is new- less than 30 miles- noise was there with old clutch.

No noise linked to operating the clutch.

Prop joints are fine- this is a new GKN unit that has covered only about 4000 miles and is always greased regularly.

Have looked for any "contact" points in lever etc but none apparent- clearance is ok around the box etc.



Re: 5 speed conversions

PostPosted: Fri Jul 02, 2010 10:43 am
by elansprint
John i,m with Tim gearstick my Tuscan has just started doing it whilst touring France drove me nuts.