gearbox oil change
Discussion
I've gone for semisynthetic 75 and an ordinary 80 in the past in preference to ATF based on an experience I had with a SEAC. When I got the car I did a load of work on it including replacing the gearbox and diff oils. When I took the gearbox sump plug out it had a very large amount of fine grey fileings on it and the ATF looked really nasty. The car had only done about 30k miles and was weeping a tad at the output end. So I replaced the oil a couple of times whilst I had the car and ended up with an EP80 with an aditional gearbox seal rejuvinator in it. I always felt that ATF in that gearbox with 300bhp was asking for long term trouble. The oils I used never gave any trouble with gear changes though that could have been because it was already worn.
Hmm, I have steered clear of using engine oils in boxes since I tried 25W50 in one, the box shifted the best it had ever done but only lasted a few hundred miles until it broke.
I since found out that gear oils have a much higher shear strength which means that they protect parts grinding against each other much better.
However as you have "got away with it" for so long, maybe it's the extra moly that has done the trick?
I since found out that gear oils have a much higher shear strength which means that they protect parts grinding against each other much better.
However as you have "got away with it" for so long, maybe it's the extra moly that has done the trick?
carsy said:
We keep hearing atf isnt good for the box. But has anyone first hand experience of boxes failing through atf. Atf is what they left the factory with and im not under the impression that boxes were forever going bang.
Quite right, they didn't go bang, just that on some boxes the gearchange becomes difficult and sometimes impossible.Why - I dont think anyone really knows - but then out of desperation, owners tried alternative methods of lubrication, yea verily some were successful, so the word goes out amongst the LT77 community that a certain type of oil change works.
Then the rumour become fact and it really does work - for some people - but not for others.
Again Why - who knows? The bottom line is - If youve got an unfriendly box you have two choices
Stay with the original recommended lube and suffer the problem or try a change.
Almost everyone I come across has agonised on this issue, but those who decide to change quite often gain an improvement.
carsy said:
We keep hearing atf isnt good for the box. But has anyone first hand experience of boxes failing through atf. Atf is what they left the factory with and im not under the impression that boxes were forever going bang.
The box was not originally designed to use ATF. It was a compromise. Gearbox failures in higher torque applications (ie, those where the car is driven hard, or where the car is heavy and/or used to tow alot) were very common. The wear in the bearings and shafts caused lots of movement, and it was not uncommon to see badly damaged casings, which effectively meant the gearbox was written off. Granted, some of the newer ATF fluids will probably work better than the original stuff, so maybe its no longer an issue if filled with modern lubes? In reference to the point made that if ATF was specced by TVR then it must be correct, please bear in mind that TVR will have simply followed the spec sheet supplied by Rover - it's not as if TVR built the box or had any hand in it's development!! A PROPERLY built and set up box, filled with SMX-S or similar will have the sweetest of changes, run cooler and be much quieter in all circumstances except on the coldest of mornings for the first mile or so when 1st to 2nd might be a bit notchy. If you've got problems beyond this then its not the oil, it's either that the box is already on the way out, or the way the box has been assembled (if it's new/reconditioned) or there is a clutch problem.
cor blimey, wot a debate ive caused
I have read all comments several times now and thankyou all
I THINK what ill do is......as I am in a warmer climate and those cold mornings are not an issue and I have no idea what is in it currently, I will try the SMX S Aussie equivalent castrol syntrax 75w 9O or syntrans 75w 85,would I be right in thinking the latter is closer to SMX S. that way it will set me a benchmark if no good ill try one or even two of the other options if still no good, well ill cross that bridge..............as I said it perfectly drivable just a bit annoying
cheers
Adam
I have read all comments several times now and thankyou all
I THINK what ill do is......as I am in a warmer climate and those cold mornings are not an issue and I have no idea what is in it currently, I will try the SMX S Aussie equivalent castrol syntrax 75w 9O or syntrans 75w 85,would I be right in thinking the latter is closer to SMX S. that way it will set me a benchmark if no good ill try one or even two of the other options if still no good, well ill cross that bridge..............as I said it perfectly drivable just a bit annoying
cheers
Adam
honestjohntoo said:
Then the rumour become fact and it really does work - for some people - but not for others.
Yes I spose it's a rumour mill, but I've been through my fair share of boxes:Boxes killed on ATF: 4
Boxes killed on SMX-S: 1? Maybe 0.
I don't know how significant this is, I started using my latest box with 6500 miles on the clock so maybe it's just the low mileage and relatively few different drivers (this is probably the most significant effect on gearbox wear).
andymadmak said:
The box was not originally designed to use ATF. It was a compromise.
Arguably, the compromise was caused by the failure of the designer to correctly specify the oil pump to handle the oil it was intended to move...Seem to recall from my motor vehicles college training that someone (Manchester Uni?) ran an engine using Coca-Cola instead of oil to prove that any lubrication is better than none. On that basis a good flood of ATF (not some that has been in 20 years, obviously) should be perfectly adequate - it's as much about cooling as keeping the meshing faces sliding.
Wedg1e said:
andymadmak said:
The box was not originally designed to use ATF. It was a compromise.
Arguably, the compromise was caused by the failure of the designer to correctly specify the oil pump to handle the oil it was intended to move...
plushuit said:
Wedg1e said:
andymadmak said:
The box was not originally designed to use ATF. It was a compromise.
Arguably, the compromise was caused by the failure of the designer to correctly specify the oil pump to handle the oil it was intended to move... 
JR said:
plushuit said:
Wedg1e said:
andymadmak said:
The box was not originally designed to use ATF. It was a compromise.
Arguably, the compromise was caused by the failure of the designer to correctly specify the oil pump to handle the oil it was intended to move... 
plushuit said:
While ATF is, in fact. only a "compromise", it is the only LT77 fluid I have never heard caused a serious problem...only complaints that shifting should be better. Experimenting with LT77 fluids is akin to Russian roulette.
Well if the dinnerladies weren't impressed, captains of industry who thought they were buying a gentleman's express in the shape of the SD1 would certainly not have been. It might not have mattered quite so much on the RangeRover but on an 'executive' car...?andymadmak said:
JR said:
plushuit said:
Wedg1e said:
andymadmak said:
The box was not originally designed to use ATF. It was a compromise.
Arguably, the compromise was caused by the failure of the designer to correctly specify the oil pump to handle the oil it was intended to move... Wedg1e said:
Well if the dinnerladies weren't impressed, captains of industry who thought they were buying a gentleman's express in the shape of the SD1 would certainly not have been. It might not have mattered quite so much on the RangeRover but on an 'executive' car...?
It's a fair point you make. Who knows what thought processes British Leyland management went through? I suspect that the box was designed by engineers accustomed to rather finer production tolerances - Ken Tomlinson had worked on aero engines before he helped design the LT77. The production versions might have betrayed a certain notchiness when cold when compared to the prototypes? I can well imagine that the conversation went something like this:Engineer: These production boxes are a bit stiff when cold
Manager: So? In the war we had to cope with far more..
Engineer: Yeah, but these boxes are going into the SD1, and the TR7, people might complain!
Manager: Complain? Pah! Our customers are hairy chested men! Men I tells yah! They'll relish the challenge of mastering the gearchange
Engineer: But what about our female customers?
Manager: Women driving our cars? Women? Really?
Engineer: Apparently so sir, according to marketing
Manager: What an awful thought. It's a changing world Bob. Well best get Gracie and the girls in the staff canteen to try a few...
andymadmak said:
Wedg1e said:
Well if the dinnerladies weren't impressed, captains of industry who thought they were buying a gentleman's express in the shape of the SD1 would certainly not have been. It might not have mattered quite so much on the RangeRover but on an 'executive' car...?
It's a fair point you make. Who knows what thought processes British Leyland management went through? I suspect that the box was designed by engineers accustomed to rather finer production tolerances - Ken Tomlinson had worked on aero engines before he helped design the LT77. The production versions might have betrayed a certain notchiness when cold when compared to the prototypes? I can well imagine that the conversation went something like this:Engineer: These production boxes are a bit stiff when cold
Manager: So? In the war we had to cope with far more..
Engineer: Yeah, but these boxes are going into the SD1, and the TR7, people might complain!
Manager: Complain? Pah! Our customers are hairy chested men! Men I tells yah! They'll relish the challenge of mastering the gearchange
Engineer: But what about our female customers?
Manager: Women driving our cars? Women? Really?
Engineer: Apparently so sir, according to marketing
Manager: What an awful thought. It's a changing world Bob. Well best get Gracie and the girls in the staff canteen to try a few...
JR said:
When I bought my first 350i one of the alternatives that I looked at was a similar aged Morgan Plus 8, the factory recommendation for was the use of two hands to engage reverse gear...
By the time the LT77 appeared, Morgan Plus 8 owners had lived through 4 years of 4-speed Moss boxes (1968-1972) and 5 years of 4-speed Rover boxes. They were grateful for the LT77, chunky shift or not. I swapped out my LT77s for Morgan R380s (pretty much a direct and simple switch). The post-1999 R380s are great Liquidly smooth and require no more than a finger to shift them. They are also rated to handle more power.
The LT77 struggle into reverse can be corrected by properly adjusting the reverse baulk plate (in the remote). One can also ease the shifting by correctly aligning and/or taking some of the tension off the gear lever.
L.
andymadmak said:
It's a fair point you make. Who knows what thought processes British Leyland management went through? I suspect that the box was designed by engineers accustomed to rather finer production tolerances - Ken Tomlinson had worked on aero engines before he helped design the LT77.
I think they missed an opportunity, they should have made 5th gear an overdrive ratio, it's not as though the V8 is short of torque. My TVR is doing 3000rpm (ish) at 80mph - the same as my company Connect with half as many cylinders and less than half the capacity.Gassing Station | Wedges | Top of Page | What's New | My Stuff