TR8 LT77 gearbox help....
Discussion
I have just completed rebuilding a TR7 V8. Having driven the car for about 50 miles, I now have an issue with the gearbox. LT77) It goes easily into first gear, then, when 2nd is selected, it goes in gear (noisily) but if I pull the stick further down, it starts to 'crunch' , this is the same when i select 3rd, and again if I were to pull the stick down it starts to 'crunch'. 4th and 5th are fine. I've read a lot about crap LT 77 boxes.... So is it a case of bin it and start again ! ??
rallypug said:
I have just completed rebuilding a TR7 V8. Having driven the car for about 50 miles, I now have an issue with the gearbox. LT77) It goes easily into first gear, then, when 2nd is selected, it goes in gear (noisily) but if I pull the stick further down, it starts to 'crunch' , this is the same when i select 3rd, and again if I were to pull the stick down it starts to 'crunch'. 4th and 5th are fine. I've read a lot about crap LT 77 boxes.... So is it a case of bin it and start again ! ??
I'll assume you are using the clutch, so this isnt the cause of the crunch....It could be anything from a clutch problem, driver problem, or gearbox problem. Be it wrong oil, synchros or other issue.
It would be easiest just to have your box rebuilt, at least then you can be sure it is not the cause of any problem.
I dont think you should dump the box before trying several things!
1 Check all the 'Remote' Rubber Mounting Bushes are not worn or loose.
2 Check the selector shaft/rod is operating directly in line with the bearing in the rear cover.
3 Was the box innards cleaned throughly before being re-used - AND
4 What lubricating oil/fluid did you choose.
To deal with points 3 and 4 you may want to consider this radical solution I devised for my really nasty LT77 way back in the late 1990's and which has stood the test of time ever since.
Furthermore, many SD1 and TVR owners have used the solution to very good effect.
Radical Cure for a Nasty 5 Speed Manual Gearbox
• Here is my 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 G/B lubricant.
• By coincidence, I had been told by an Ex-Mobil employee that Mobil 1 or Castrol RS at 0W40 or 5W40 viscosity, respectively, 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/applicator and is available from Halfords, Ebay, 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.
Like I say, it was an amazing gearbox transformation and providing a manual LT77 gearbox is not actually damaged or simply worn out then the suggested solution has got to be worth a try before removing the box for repair/replacement.
So! Was it the Fully Synthetic Castrol RS 5W40/Mobil 1 0W40 Lubricant or was it the Molyslip Gearbox Treatment that did the trick? Or was it the combination of the two?
Personally I think it was the combination of both treatments, but every gearbox will be in a different state/condition, so one cant predict it will always be effectve but I have many feedback testimonies from fellow LT77 users who took the courage to try my solution and came back smiling! You could be smiling too!!!!
All the above was taken from my web pages.
Ramon
www.vintagemodelairplane.com
1 Check all the 'Remote' Rubber Mounting Bushes are not worn or loose.
2 Check the selector shaft/rod is operating directly in line with the bearing in the rear cover.
3 Was the box innards cleaned throughly before being re-used - AND
4 What lubricating oil/fluid did you choose.
To deal with points 3 and 4 you may want to consider this radical solution I devised for my really nasty LT77 way back in the late 1990's and which has stood the test of time ever since.
Furthermore, many SD1 and TVR owners have used the solution to very good effect.
Radical Cure for a Nasty 5 Speed Manual Gearbox
• Here is my 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 G/B lubricant.
• By coincidence, I had been told by an Ex-Mobil employee that Mobil 1 or Castrol RS at 0W40 or 5W40 viscosity, respectively, 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/applicator and is available from Halfords, Ebay, 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.
Like I say, it was an amazing gearbox transformation and providing a manual LT77 gearbox is not actually damaged or simply worn out then the suggested solution has got to be worth a try before removing the box for repair/replacement.
So! Was it the Fully Synthetic Castrol RS 5W40/Mobil 1 0W40 Lubricant or was it the Molyslip Gearbox Treatment that did the trick? Or was it the combination of the two?
Personally I think it was the combination of both treatments, but every gearbox will be in a different state/condition, so one cant predict it will always be effectve but I have many feedback testimonies from fellow LT77 users who took the courage to try my solution and came back smiling! You could be smiling too!!!!
All the above was taken from my web pages.
Ramon
www.vintagemodelairplane.com
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