Strange gearbox/clutch problem (V8/LT77)

Strange gearbox/clutch problem (V8/LT77)

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Discussion

adam quantrill

Original Poster:

11,535 posts

241 months

Saturday 18th February 2012
quotequote all
Well I've been having a strange problem over the past week or so, symptoms are:

- Gets stuck in 1st especially when giving it beans
- Sometimes gets stuck in 3rd too.
- Crashing (lack of syncro) into 2nd or 3rd, fairly often, occasionally 4th or 5th.
- Usually bad when moving (i.e. rear wheels input to back of box) and OK when stationary.
- Sometimes works perfectly.
- Pumping the clutch 10 times sometimes makes it better.
- It isn't losing fluid, and the clutch pedal feels solid enough. The bite point feels normal and it will allow the engine to rev as you press past the bite point.
- Reverse works perfectly no crunching
- No problems with the remote linkage bushes - it's completely solid.

So I tried bleeding the clutch today, and took it for a spin, it was a bit better but some of the symptoms reappeared.

Just now I let some gearbox oil out and cleaned the magnetic plug - not a huge amount of filings on there (I've seen much worse). The let-out oil is a bit silvery. I topped up but it took a litre - much more than I let out. I shall report back if it's any better but this will be tomorrow now as I have started on the wine.

So - any ideas? Do I have to buy an endoscope to check out the release fork/pivot?

It's an 'E' suffix box by the way - and I just noticed that the oil drain plug is a much bigger diameter than the usual LT77 size...

I have taken to double-declutching to continue driving but I don't like the time delay changing gear - lucky I have bags of torque so can go into less-gear-changes mode!!

Lean Machine

2,714 posts

164 months

Sunday 19th February 2012
quotequote all
To me, it sounds like clutch hydraulic master cylinder fault. They don't always leak, but the internals malfunction. Possible slave cylinder for the same reason. Good luck.

Tony. TCB.

adam quantrill

Original Poster:

11,535 posts

241 months

Sunday 19th February 2012
quotequote all
Yeah I was wondering about this but what could go wrong with a piston in a bore? If it's moving and not leaking it must be displacing the fluid (I have bled out any air). Same applies to the other end - the fluid is incompressible so must move the piston. It's all a bit wierd.

I have one of each as a replacement so if the g/b fluid top up doesn't work that's the next easiest thing to change. Then after that it's the release arm, but I shall take a look while the slave is out.

carsy

3,018 posts

164 months

Sunday 19th February 2012
quotequote all
Adam, i would also say clutch master. Having already fitted a new slave, i also had similar experiences. Mine when hot would get very sticky and hard to move out of gear when going for a gear change. I was unsure of the problem at this stage. Next thing that happened was when reversing out of a steep incline drive and thereby having to slip the clutch, when i came to depress the clutch fully at the end of the drive it was still engaging and driving and i had to kill engine to stop flying out into the road. I also wasnt loosing fluid. I took the cap of the clutch reservouir and pressed the clutch. In doing so the fluid level would rise. Clearly the fluid wasnt going in the direction its supposed to ie to the slave.

The rubber seals get shot and allow fluid to get past them and go where it shouldnt. On mine it was getting past the end seal and allowing it back up into the reservouir rather than pushing it down to the slave.

mrzigazaga

18,534 posts

164 months

Sunday 19th February 2012
quotequote all
Hi Adam...I had a similar problem with a 420 rover..I had a new clutch fitted and within a week it was doing the same thing..I took it to another garage and he pointed out that the release fork was seized so i went back to the original garage and told them even though they didnt believe me..They ended up paying someone else to fit another clutch..Which was a bit strange but they said the same thing about the release fork..Ziga

TOPTON

1,514 posts

235 months

Sunday 19th February 2012
quotequote all
If the clutch isn't slipping under acceleration, you don't say it is. 3rd gear 30mph and floor it should find slipage. You say you've got bags of torque so doesn't sound like it.
It sounds like the clutch is not disengaging properly when the pedal is pushed.

I would be 1st looking at the slave cylinder seals. They don't always leak fluid out, so bleeding won't fix cos there is no air in there. When worn the rubber seals sometimes allow fluid to pass back beside them instead of pushing it all down the pipe as it were. Therefor not giving full clutch travel

The same can happen with master cylinder seal, again bleeding won't help as there is no loss of fluid


E Ponym

1,233 posts

266 months

Sunday 19th February 2012
quotequote all
adam quantrill said:
Yeah I was wondering about this but what could go wrong with a piston in a bore? If it's moving and not leaking it must be displacing the fluid (I have bled out any air). Same applies to the other end - the fluid is incompressible so must move the piston. It's all a bit wierd.

I have one of each as a replacement so if the g/b fluid top up doesn't work that's the next easiest thing to change. Then after that it's the release arm, but I shall take a look while the slave is out.
There is a valve at the end of the master piston that is normally open when the clutch is not depressed. This valve allows fluid to go back into the reservoir if it gets hot and expands.

When there is pressure put on the piston, this valve should be the first thing to close so the pressure gets directed to the slave cylinder, if this valve leaks then the slave might not get much pressure and may be a bit hit-and-miss. Get somebody to look into the reservoir when you push the clutch to see if they can see signs of this back-flow.

The characteristics of this type of failure are no fluid loss (it stays inside the system) and the pedal may be a bit lighter than normal - easier to detect on brake systems but you could feel it on the heavy clutch of a modified V8, has it been feeling lighter lately?

Change the clutch master seals before tou take the engine out.

ETA - the seal is the little springy bit on the end of the piston, less than a quarter of an inch round.

Russ

adam quantrill

Original Poster:

11,535 posts

241 months

Sunday 19th February 2012
quotequote all
That makes perfect sense! Master cylinder change it is...

convert

3,747 posts

217 months

Sunday 19th February 2012
quotequote all
Adam, If you need an endoscope let me know, I can post one to you.

adam quantrill

Original Poster:

11,535 posts

241 months

Monday 20th February 2012
quotequote all
All in good time - if it's just the master then I won't do.

In the mean time progress with the replacement has been slow.

Firstly the clevis pin is siezed on the clutch lever. So I undid the rod from the lever bracket.

Then the new rod has a different thread - so I swapped over the rods.

Lastly the new clutch has a smaller thread on the pipe union than the old one. So what do I do - either get a new mating end and re-flare the pipe? Or shall I drill out the hole and tap it for the original connector - in which case what thread is it - 3/8" UNF possibly? Not sure which is the best option.... either way it's a load of hassle getting the pipe end sorted.... or buying some taps.

The Hatter

988 posts

169 months

Monday 20th February 2012
quotequote all
Hi Adam,

I had this problem on the SEAC and bought an adapter... and two arived so I have a spare. PM me your address and I'll send it to you.

Cheers,

Martin.

HOTTY

669 posts

173 months

Monday 20th February 2012
quotequote all
Hi Adam

Sounds a bit more, like the clutch is shagged, hopefully not but how many miles have you done on it.

Now don't try and tell me all driven with care, as i followed behind you on the Sunday trip to the pub not last BBWF but one one before eek

bets of luck

Hotty

adam quantrill

Original Poster:

11,535 posts

241 months

Tuesday 21st February 2012
quotequote all
Ha ha - well when I get the hydraulics sorted I will shag it some more!!!

In the mean time I got a smaller brake union nut from a local garage and stuck it on the pipe and flared it (made a flaring tool for the purpose).

I have the new master on but it isn't taking fluid from the reservoir into the system, so I am hoping to borrow a pressure bleeding kit tomorrow to force the fluid in.

Anyone experienced this problem before - it is a bit odd?


wild rover

445 posts

180 months

Wednesday 22nd February 2012
quotequote all
Could the clutch fork be starting to break up/flexing at the pivot, giving you the clutch drag if it is not the master. I have a spare fork.

GV

2,366 posts

223 months

Wednesday 22nd February 2012
quotequote all
I have the new master on but it isn't taking fluid
the reservoir into the system, so I am hoping to borrow a pressure bleeding kit tomorrow to force the fluid in.

Anyone experienced this problem before - it is a bit odd?

I had the same problem and it turned out that the master needed a good bleeding. I still think it needs another bleed to be completely sure.

I also spoke with the people who rebuilt my gearbox last year - they reckon it may be the oil I'm using in the box which should be ATF - I've also read that Castrol SMX is a good oil to use.


Edited by GV on Wednesday 22 February 16:31

adam quantrill

Original Poster:

11,535 posts

241 months

Wednesday 22nd February 2012
quotequote all
Well I put a pressure system on top of the reservoir (DIY - an old cap, a rugby ball inflation needle and an electric compressor) but even that struggled to force any fluid in. So I now think there is a defect with the new master cylinder.

The old cylinder looks great inside - no signs of wear or scoring - so I may just try and get a seal kit for it as I have to take off the new master anyways. Hmmmm.

GV

2,366 posts

223 months

Thursday 23rd February 2012
quotequote all
Have you tried bench bleeding?

honestjohntoo

576 posts

215 months

Thursday 23rd February 2012
quotequote all
adam quantrill said:
The bite point feels normal and it will allow the engine to rev as you press past the bite point.
- Reverse works perfectly no crunching
- No problems with the remote linkage bushes - it's completely solid.

I topped up but it took a litre - much more than I let out.
Cant help thinking that the first observation above rules out a clutch problem and the second observation may have indicated running on a low oil level.

The LT77's generally mated with RV8's were specified to use ATF, but apparently that was a compromise to resolve earlier clunky issues too.

Then loadsa users started to experience symptoms similar to what you describe.

The classic 'old age' cause/solution was worn remote mounting bushes, but it seems you have ruled that out.

So if it ain't the clutch and it ain't the bushes and it ain't knackered due to low oil level, then it's likely to be down to the choice of lube.

I had this problem in 1996 and resolved it once and forever! Yes! 16 years and counting. smile Thus:


Radical Cure for a Nasty 5 Speed Manual Gearbox

• Here is a radical solution to an unfriendly 5-speed gearbox. Truly nasty. It baulked at will and was notchy to a fault. In fact it was very, very hard work. This was my last resort.
• During a routine gearbox oil level check, I noticed how dirty the lubricant had become so it was obvious it had to be flushed and changed. It had the recommended ATF which Rover had been forced to specify, because the gearbox was unreliable when filled with conventional lubricant.
• By coincidence, I had been told by an Ex-Mobil employee that Mobil 1 or Castrol RS at 0W40 or 5W40 viscosity were considered by the trade to be a better replacement than ATF in the Rover 5 speed box and gave a much improved performance.
• With the car on axle stands and the back wheels off the ground I drained the box and re-filled it with a flushing mixture of 2:1 white spirit and ATF (I did say radical and it was a last resort!).
• With the engine running at idle speed only, I put the car through all the gears and let the drive train run off-load for 5 to 10 minutes.
• Upon draining the flushing mixture I was amazed at the filthy color and state of the drained fluid. It was as black as ebony with lots of sediment!
• I repeated the above with a clean batch of mixture to flush out the residues. One can imagine the washing machine action inside the box allowed the solvent component to reach into every recess.
• The box was then refilled with 5W40 "Castrol RS" (0W40 "Mobil 1" is virtually the same and I have subsequently used both with no discernable difference).
• I then added a recommended dose of Molyslip Gearbox Treatment. This stuff comes in a tube-like applicator and is available from Halfords, etc.
• The transformation was miraculous. It has run since the late 1990's without any of the original symptoms and is a total pleasure to use.
• The oil has been replaced thrice in that period with Mobil 1 and the same Molyslip gearbox additive each time.
• As an experiment I used the leftover Molyslip treatment in the rear axle differential.
• After thoroughly warming the axle with an electric fan heater I sucked out all the old lubricant with a large medical syringe and some flexible plastic tube. It was then refilled with fresh hypoid oil (as specified) and the mentioned Molyslip treatment.
• The rear axle differential was transformed. Taking both treatments into account, the whole drive train has been silky smooth ever since.


Refilling a Manual Gearbox

• When topping up or refilling a manual box, the oft recommended method using squeezy bottles and flexible pipes has the disadvantage of proving Newton's 2nd Law of gravity that states: "It's easier to oil your armpit than to fill a gearbox from below!"
• A neat method to refill or top up the gearbox is to run a large bore plastic hose from the filler hole, up past the bell-housing and into the rear of the engine bay.
• Fit and secure a suitable funnel on top and pour in the replacement oil without difficulty. Do it slowly to prevent overflow.

So! Was it the lube or was it the Moly? Or was it the combination of the two? Dunno! But there are many feedback testimonies from fellow LT77 users who took the courage to try my solution and came back smiling! You could be smiling too!!!! rolleyes

adam quantrill

Original Poster:

11,535 posts

241 months

Thursday 23rd February 2012
quotequote all
Yes thanks Ramon I was hoping it was the clutch rather than the box, but with the symptoms it has maybe I'm "clutching at straws"....

Campbell

2,499 posts

282 months

Thursday 23rd February 2012
quotequote all
honestjohntoo said:
adam quantrill said:
The bite point feels normal and it will allow the engine to rev as you press past the bite point.
- Reverse works perfectly no crunching
- No problems with the remote linkage bushes - it's completely solid.

I topped up but it took a litre - much more than I let out.
Cant help thinking that the first observation above rules out a clutch problem and the second observation may have indicated running on a low oil level.

The LT77's generally mated with RV8's were specified to use ATF, but apparently that was a compromise to resolve earlier clunky issues too.

Then loadsa users started to experience symptoms similar to what you describe.

The classic 'old age' cause/solution was worn remote mounting bushes, but it seems you have ruled that out.

So if it ain't the clutch and it ain't the bushes and it ain't knackered due to low oil level, then it's likely to be down to the choice of lube.

I had this problem in 1996 and resolved it once and forever! Yes! 16 years and counting. smile Thus:


Radical Cure for a Nasty 5 Speed Manual Gearbox

• Here is a radical solution to an unfriendly 5-speed gearbox. Truly nasty. It baulked at will and was notchy to a fault. In fact it was very, very hard work. This was my last resort.
• During a routine gearbox oil level check, I noticed how dirty the lubricant had become so it was obvious it had to be flushed and changed. It had the recommended ATF which Rover had been forced to specify, because the gearbox was unreliable when filled with conventional lubricant.
• By coincidence, I had been told by an Ex-Mobil employee that Mobil 1 or Castrol RS at 0W40 or 5W40 viscosity were considered by the trade to be a better replacement than ATF in the Rover 5 speed box and gave a much improved performance.
• With the car on axle stands and the back wheels off the ground I drained the box and re-filled it with a flushing mixture of 2:1 white spirit and ATF (I did say radical and it was a last resort!).
• With the engine running at idle speed only, I put the car through all the gears and let the drive train run off-load for 5 to 10 minutes.
• Upon draining the flushing mixture I was amazed at the filthy color and state of the drained fluid. It was as black as ebony with lots of sediment!
• I repeated the above with a clean batch of mixture to flush out the residues. One can imagine the washing machine action inside the box allowed the solvent component to reach into every recess.
• The box was then refilled with 5W40 "Castrol RS" (0W40 "Mobil 1" is virtually the same and I have subsequently used both with no discernable difference).
• I then added a recommended dose of Molyslip Gearbox Treatment. This stuff comes in a tube-like applicator and is available from Halfords, etc.
• The transformation was miraculous. It has run since the late 1990's without any of the original symptoms and is a total pleasure to use.
• The oil has been replaced thrice in that period with Mobil 1 and the same Molyslip gearbox additive each time.
• As an experiment I used the leftover Molyslip treatment in the rear axle differential.
• After thoroughly warming the axle with an electric fan heater I sucked out all the old lubricant with a large medical syringe and some flexible plastic tube. It was then refilled with fresh hypoid oil (as specified) and the mentioned Molyslip treatment.
• The rear axle differential was transformed. Taking both treatments into account, the whole drive train has been silky smooth ever since.


Refilling a Manual Gearbox

• When topping up or refilling a manual box, the oft recommended method using squeezy bottles and flexible pipes has the disadvantage of proving Newton's 2nd Law of gravity that states: "It's easier to oil your armpit than to fill a gearbox from below!"
• A neat method to refill or top up the gearbox is to run a large bore plastic hose from the filler hole, up past the bell-housing and into the rear of the engine bay.
• Fit and secure a suitable funnel on top and pour in the replacement oil without difficulty. Do it slowly to prevent overflow.

So! Was it the lube or was it the Moly? Or was it the combination of the two? Dunno! But there are many feedback testimonies from fellow LT77 users who took the courage to try my solution and came back smiling! You could be smiling too!!!! rolleyes
I like the sounds of that, cleaning the internals of the box and using a good oil to start again.

Adam im sue you will get to the bottom of your box probs, running a flush fluid through cant hurt.

Cambelt