is the lt77 gearbox man enogh for the job

[993phill]

put an lt77 gearbox in my tuscan converstion {because i had one already out of a 400se} but has now been mated to a rv8 500
some people say it will only last a short while some say it will be ok
any ideas

[JR]

Although derived from a sixties Triumph design, SteveH has been pushing mega hp through it for quite a while now :-)

[Boosted LS1]

It's down to your final drive gearing imo and how fast you can get through the gears. I had a TT 5.1 with 2.84 diff. Never broke the box built by ken tomlinson. Friend had a similar engine and low diff (3.9) ratio, broke lots of boxes.

I'd use it

Boosted.

Edited by Boosted LS1 on Friday 7th September 23:37

[JR]

Hi Mike. That's odd how you can have two posts seemingly identical but edited at different times.

[shpub]

JR said:

Although derived from a sixties Triumph design, SteveH has been pushing mega hp through it for quite a while now :-)

The old LT77 goes back even earlier... 1940s Jaguar 4 speed IIRC and it is stronger than many give it credit.

[Boosted LS1]

JR said:

Hi Mike. That's odd how you can have two posts seemingly identical but edited at different times.

Hi JR, strange but it happens. Got rid of one of them I'll have to call for that chat!

[GreenV8S]

Boosted LS1 said:

It's down to your final drive gearing imo and how fast you can get through the gears. I had a TT 5.1 with 2.84 diff. Never broke the box built by ken tomlinson. Friend had a similar engine and low diff (3.9) ratio, broke lots of boxes.

Any idea why the 'box suffered more with the lower final gearing? Given that the tyre acts as a torque limiter I'd have thought that lower gearing would put less load on the 'box. I wonder whether there may have been some other factor involved - different tyres, half shafts, clutch, driving style?

[Boosted LS1]

GreenV8S said:

Boosted LS1 said:

It's down to your final drive gearing imo and how fast you can get through the gears. I had a TT 5.1 with 2.84 diff. Never broke the box built by ken tomlinson. Friend had a similar engine and low diff (3.9) ratio, broke lots of boxes.

Any idea why the 'box suffered more with the lower final gearing? Given that the tyre acts as a torque limiter I'd have thought that lower gearing would put less load on the 'box. I wonder whether there may have been some other factor involved - different tyres, half shafts, clutch, driving style?

Driving style, he hammered it off the line and broke the box when he got traction all of a sudden. My gears were more spread out and I didn't hammer it in first gear or second come to that. There wasn't any point.

Oh my box was built by KT so that may have had a lot to do with it

Edited by Boosted LS1 on Saturday 8th September 15:00

[GreenV8S]

It's my view that the transmission suffers far more from shock loads than from smooth sustained power, which is why I've gone for a very wide power band now - to reduce the number of gear changes, gaining performance and giving the transmission an easier time of it. This is contrary to the other popular view that torque kills gearboxes and it's better to go for something that will rev rather than something with shed loads of torque. It seems to be working so far - my (KT built) LT77 seems to be coping OK so far with the thick end of 400 lb-ft. Mind you I'm a long way shy of the sort of power and torque that Steve Heath has to play with and not at all surprising that he has to take more drastic measures. Still, I reckon the LT77 is a good old box which is often underrated.