Gearbox dead - where from here ?

Gearbox dead - where from here ?

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gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
I've had my 4.0L engine upgraded to 5.0L using the V8D package which has been running very nicely, but it looks like my gearbox has let go. It's a V8S so has the same LT77 as the early Chimearas and Griffiths ( I think). It makes a horrible grinding noise in all gears, related to road speed. I assume the extra torque has been too much for it.

What are my options from here ? Should a rebuilt standard LT77 be OK or should I be upgrading something in the gearbox or even switching to another gearbox ? Any suggestions who could do this ?

Thanks

Note - I've posted in general rather than S Series as I believe some of the options may come from the Chim/Griff



Oldred_V8S

3,714 posts

237 months

Thursday 2nd October 2014
quotequote all
I would have thought a recon LT77 will be fine.

These things were built to move a large Range Rover around and occasionally up steep inclines, with loads of torque, so unless you are spanking the car around permanently I would think another LT77 should be fine. The only reason TVR moved to the T5 was that Rover stopped producing the LT77.

QBee

20,905 posts

143 months

Thursday 2nd October 2014
quotequote all
Oldred_V8S said:
I would have thought a recon LT77 will be fine.

These things were built to move a large Range Rover around and occasionally up steep inclines, with loads of torque, so unless you are spanking the car around permanently I would think another LT77 should be fine. The only reason TVR moved to the T5 was that Rover stopped producing the LT77.
+1 - the LT77 was fitted to the early 430 Chims, which produce not far short of 500 power/torque, so should be well capable of handling the power of your V8D lump.

Nice, aren't they? The V8D lump, I mean.

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
Thanks. I was planning to do a lot more track days next year so it will be in for quite a bit of spanking. In fact it was a bit of spankage this year that caused the issues with this gearbox. Is there a weak point in the box that could be improved while it is being refurbished ? Any recommendations for specialists ?

QBee

20,905 posts

143 months

Thursday 2nd October 2014
quotequote all
You will need advice as to whether it will fit etc, but this may be the sort of thing you need?

click here

TvrJohn

1,058 posts

254 months

Thursday 2nd October 2014
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you need to contact Reid Racing ? supplies the TVR Challenge teams

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
QBee said:
+1 - the LT77 was fitted to the early 430 Chims, which produce not far short of 500 power/torque, so should be well capable of handling the power of your V8D lump.

Nice, aren't they? The V8D lump, I mean.
It was a real pain getting it running with the megasquirt but very nice now. Checking the dyno plot, it says 314/328 peak bhp/torque so that's well below those 430 Chims you mention although 500bhp sounds a lot from a 4.3L, no ?

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
TvrJohn said:
you need to contact Reid Racing ? supplies the TVR Challenge teams
Is that Readman Racing / Grantura Engineering ? Their website refers to BorgWarner T55 gearboxes but not LT77. Is the LT77 used in Challenge cars ?

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all


From this thread : http://www.pistonheads.com/gassing/topic.asp?t=125...

"The LT 77 was last used in 1994 and has a Suffix H - this is a bullet proof box capable of running 300 Hp and 280 Ft Lbs. It has widened gears, larger diameter layshaft and has a dual syncro on 1st & 2nd. The oil pump was also increased in width. The H was also known as the LT77S.

Go search for the lettering of at least G but preferably H on the box."

My engine exceeds this spec ??

brett84

1,291 posts

152 months

Thursday 2nd October 2014
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I'm looking to get mine done next year and have been recommended these guys
http://www.ashcroft-transmissions.co.uk

peteA

2,680 posts

233 months

Thursday 2nd October 2014
quotequote all
gifdy said:
It was a real pain getting it running with the megasquirt but very nice now. Checking the dyno plot, it says 314/328 peak bhp/torque so that's well below those 430 Chims you mention although 500bhp sounds a lot from a 4.3L, no ?
I think he meant Griff / Chim 500 ie 5 the litre V8 engine - TVR 'stated' 340 Bhp from memory so yours sound healthy!

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
peteA said:
gifdy said:
It was a real pain getting it running with the megasquirt but very nice now. Checking the dyno plot, it says 314/328 peak bhp/torque so that's well below those 430 Chims you mention although 500bhp sounds a lot from a 4.3L, no ?
I think he meant Griff / Chim 500 ie 5 the litre V8 engine - TVR 'stated' 340 Bhp from memory so yours sound healthy!
Oops smile Makes sense

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
brett84 said:
I'm looking to get mine done next year and have been recommended these guys
http://www.ashcroft-transmissions.co.uk
Thanks - from their website they look like they know what they're talking about. I'll give them a ring

NTEL

5,051 posts

239 months

Thursday 2nd October 2014
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Also, speak to Brian Hosfield of Lawfield Engineering. He builds and repairs boxes for some Tuscan Challenge cars etc

QBee

20,905 posts

143 months

Thursday 2nd October 2014
quotequote all
gifdy said:
QBee said:
+1 - the LT77 was fitted to the early 430 Chims, which produce not far short of 500 power/torque, so should be well capable of handling the power of your V8D lump.

Nice, aren't they? The V8D lump, I mean.
It was a real pain getting it running with the megasquirt but very nice now. Checking the dyno plot, it says 314/328 peak bhp/torque so that's well below those 430 Chims you mention although 500bhp sounds a lot from a 4.3L, no ?
Sorry, that's not clear - I meant not far short of Chim 500 power and torque levels. The 430 makes about 275 of each.

Edited by QBee on Thursday 2nd October 20:41

TV8

3,118 posts

174 months

Thursday 2nd October 2014
quotequote all
Noise as described doesn't hold much hope, however....try diff lock gear box oil. I had a LT77 gearbox and on my first track day with the car, the synchro's crunched badly once the oil got hot. Changed to diff lock oil and much better gear change and a quieter gearbox!

http://www.difflock.com/evolution1

phillpot

17,105 posts

182 months

Thursday 2nd October 2014
quotequote all
gifdy said:
It makes a horrible grinding noise in all gears
I'm guessing 5th is an overdrive gear in the LT77 so "normally" things should be a bit quieter in 4th because the drive goes straight through, lot less load on the bearings/gears?

Have you tried draining the oil to see if it looks "very metallic" or maybe a tooth or two will fall out (some gearbox's have a built in magnet to hold metal particles)?

gifdy

Original Poster:

2,065 posts

240 months

Thursday 2nd October 2014
quotequote all
phillpot said:
gifdy said:
It makes a horrible grinding noise in all gears
I'm guessing 5th is an overdrive gear in the LT77 so "normally" things should be a bit quieter in 4th because the drive goes straight through, lot less load on the bearings/gears?

Have you tried draining the oil to see if it looks "very metallic" or maybe a tooth or two will fall out (some gearbox's have a built in magnet to hold metal particles)?
I'll have a look at the oil but pretty sure it's the box. Ashcroft say the LT77 isn't strong enough for this torque level and recommend the R380 instead. I'll also swap the oil for this difflock stuff to see if it will quiten it while I work out what to do.

Thanks for advice so far.

Hoover.

5,988 posts

241 months

Thursday 2nd October 2014
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The Lt77 is a relatively cheap gearbox to get refurbed ....... I however choose to fit a T5 in it's replacement

FlipFlopGriff

7,144 posts

246 months

Friday 3rd October 2014
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My precat Griff also has a T5. Apparently easier to change the clutch too.
FFG