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LT77 gearchange
Scotty - 13/9/10 at 06:46 AM

hi all
have finally decided to uprate the v8 engine this winter (aiming for 275bhp )
BUT
have a problem with the gear changing, the cluch seems ok, (will roll backwards on hill in first with clutch in) but is difficult to take out of gear in first or third, others seem OK
If i change gear slowly, no problems. but if i try for quick gearchanges, it crashes the box all times
any ideas anyone ?

cheers in advance

Agriv8 - 13/9/10 at 07:05 AM

1, the ubbers between the gearchange housing and gear selctor may be worn periched.

2, the gearchange unit is unboltable so take it off and check the movement if free.

3, what oil are you running in the LT77 ? IIRC ATF is recomended as this improves gearchange ( please check ) .

regards

agriv8

britishtrident - 13/9/10 at 07:27 AM

Special oil grade for these gearboxes --- MTF94


In earlier years ATF or 10w/40 engine oil was recommended as a stop gap measure until MTF94 was developed specifically for Rover Group to counterr oil drag and needle roller bearing lubrication problems which were encoutered with originally specified 80 grade GL4 gear oil.



[Edited on 13/9/10 by britishtrident]

Scotty - 13/9/10 at 12:52 PM

thanks for the input. Will check
cheers

wilkingj - 13/9/10 at 01:59 PM

Do NOT use any thick type gear oil in an LT77 box ie EP75/80/90.

Most LT77's are reccomended to run on ATF. Whilst this sounds a bit daft, its not. There is an internal oil pump in LT77gearboxes and it needs the thinner ATF to work successfully.

I dont know what the MTF 94 is, so cant comment. However I ran my Landy for 13 years with ATF in the LT77 box and did over 100,000 miles on it, and it was still going well when I sold it. My mate who bought it has been running it for the last 3 years, without problem, but I dont know how many miles he has done since, probably at least another 20K as its his daily driver too.

(I Would need to get the manual out to give the exact Spec of the ATF)

britishtrident - 13/9/10 at 03:55 PM

MTF94 was developed for these boxes it is essentially an ATF without the friction additive.

The friction additive is the same stuff used to in LSD oil --- really not something you want in an oil if you don't need it.

10w/40 engine oil was specified before that but it is a a little short of EP additive.


Rover found MTF 94 made such an improvement they started using it in the front wheel drive transmissions.

scudderfish - 13/9/10 at 04:08 PM

A lubricant with a friction additive.......

britishtrident - 13/9/10 at 08:09 PM

quote:
Originally posted by scudderfish
A lubricant with a friction additive.......



Friction modifier additive as required by LSDs, with plate type LSDs the ammount of friction modifer added to the oil alters the slip-grip breakaway characteristic of the diff in more formal terms the relationship between static and sliding friction.

Tradditional automatics to the classic pattern originally developed by Borg Warner are planetary transmissions the brake bands that select the ratios also work on friction.
In the 1960s and 1970s when the Borg Warner 35/45/65 box was used by many manufacturers. The gear change characteristic of these autoboxes could be altered by the ammount of friction additive in the transmission fluid. Manufacturers had the choice of specifying a choice between TQF (using Castrol grade designation) or TQA. TQF was used by Ford, BL and Triumph and gave a more sporty ratio change. TQA was used by Rootes, Rover and Jaguar and gave a smoother more slurred gear ratio change.



[Edited on 13/9/10 by britishtrident]

Scotty - 14/9/10 at 06:49 AM

wow!
nice one chaps
better dig out the oil to see what we used
thanks again

Agriv8 - 14/9/10 at 10:28 AM

Amazing what you can learn on here - cheers for that Britishtrident .

I know we used ATF on the V8 off road buggy but that wold be chaged evey 3 or 4 meets due to contamination so used ATF as it relativley was cheep to replace

regards

Agriv8