Compression or Gearbox?

Davoe,

thanks for your reply, you are convinced it is the compression?
Don't know the degree of the hill but depending on weight in the car it chugs quicker than every 30 secs. If I load it up full gear for a trip it already does it on a bit of an incline on a parking spot!

I wouldnt say convinced but with my limited mechanical knowledge I am unsure it could be any thing else a compresion test will reveal all but make sure you either take it to a mechanic or use a proper diesal comp gauge and know how to use it coz it is different than a petrol one
results should be
3432 desirable down to 2452 minimum

This is normal even on normal compression, rings are designed to hold compression for a fraction of a second only, if you leave it in gear on a slope compression will slowly escape through the ring's gaps.
When we do driver training and stall vehicles on slopes, they all slowly move stroke by stroke back down the hill.
That is what you use the handbrake for!!

GU from driving plenty of yotas I havnt had an issue with them holding on by compression including parking them in declines and doing driver training. Some leak back will occur but it sounds like it may be a bit more than normal. like I said a person posted about her vehicle moving stroke by stroke down a hill during driver training and the trainer told her her compression was down after posting asking for advice she had it tested it confirmed it was.

GU and Davoe,

the issue is certainly more severe than normal, I have had a few 4wd's and even last year the car could just be parked on the street, fully packed up without an issue. NOw however without a load I have to be very carefull where I park it as it it might roll by closing the door when I get out! So if it might be the compression, what would be the way to solve it, if there is any?
Joost

firstly adjusting the handbrake will make it safe. When doing a compression test if a cylinder is down the mechanic will put a squirt of oil into the cylinder to seal the rings if the compression remains down it is the valves if it comes up it is the rings. At the moment you are at the mercy of everyone with an opinion (like me) for about 1hrs labour a mechanic will be able to tell you for sure what your compressions are (the max and min I gave you are from the gregorys manuel) then you will be in best position to decide what to do (If it does need a rebuild big dollars)

Top Cat.. certainly dont want to start an argument and not interested if it does but just thinking about your staement about using 1st and then lowrange to hold the vehicle on the slope.

To me that would INCREASE the mechanincal advantage of the weight over the compression of the engine, ie it woul be easier for the vehicle to move down the lower the gearing was. To me the 'hardest' a vehicles weight could movea vehicle would be 5 gear high range?
So rather than allowing small movements at the wheels be small movements at the engine, small movements at the wheels would try to force large movements at the engine and give more chace of compression locking the vehicle up. Just a thought, never tried it in practice and it just got me thinking.

Me I would be not thinking about compression etc and i would be FIXING MY HANDBRAKE!!!!!

That is what is not holding the vehicle, the engine should not be RELIED upon to hold the vehicle, only used in emergency operations like stall starts etc!

Matt.

Matt,

Sorry mate ol' Top Cat is correct. Think of it as a lever. The bigger the lever the easier something is to move. The higher gear your in the bigger the lever ie. you have to turn the wheels say 4 complete times to turn the engine once, so you spreading out the amount of work involved - EASY. Put it in low range 1st and the "lever" has just been shortened to a toothpick ie. you have to do all the work involved in turning over the engine once in only say a 1/4 of a wheel turn, so your trying to do alot of work in a short space - HARD.

Hope that sort of makes sense. If it doesn't - just believe it anyway cause it does work. Try it out ya self.

PS. Thats why you also always roll start a vehicle in 2nd or 3rd gear because its easier to turn the motor over in those gears than in 1st gear - especially if your trying to push it.

Cheers,
Hughesy

Matt,

From towing vehicles over the years, it is always easier to tow start a vehicle in a higher gear. So I'd agree with Top Cat.

But you are dead right, he needs to adjust/fix his handbrake!!! What's going to be said if a child gets run over, " the tojo wouldn't stop moving"

hooroo...

No probs matt.........and I think its been well answered.

Its also true that you should use a higher gear in order to clutch start a car..........for the same reason.

Personally I would use the highest available........but u need to have a good feel for driving and use of the clutch or u can stall it as quick as u start it......lol.

Good question never the less and while u may have learnt something today.........dont panic, cos so did I in another thread.

Thats what life is all about........none of us knows everything........ but the smart ones are not afraid to learn.

Cheers.

OK OK hold on guys.....

This all depends on how you look at it, what is 'harder' to do...

Just thihk of it like this.. what is easier, turning the engine over quickly or turning the engine over very slowly....try it!!!! We all do when adjusting valves, you know finding TDC by spinning the fan. If you go slow, the compression leaks past the rings and it turns over, do it quickly and it HITS the compression and bounces back!

I think that answers MY question for using it as a BRAKE (just needed to stop and think more myself). But to the response about towstarting (not that I mentioned it) the reason you tow start in second or third is not for the 'hardness' of the motor to turn....its all about speed and throwing the motor over quickly enough to make if run, without it imediately stopping due to the revs too low, ie wheel speed.

But thanks for the replies anyway, it just made me have to stop and really work the grey matter!!

Matt.

I confirmed this today, parked on a hill in 1st and vehicle went nowhere confirming my post that compression should hold it. Then I put T.C information to the test and tried it in 2nd and chug chug chug it went!! eg the lower the gearing the more likely compression is to hold it

Davoe..........The idea is that if u are facing downhill.........then DONT select first gear..........select reverse.

And opposite if you are facing uphill.

I honestly thought this was standard knowledge.

Dont they teach you that when u do your learners and stuff??

TC it was a test that I was conducting to see how much of a hill it would take and still hold on compression. Also I believe that the idea of using 1st and reverse is a bit overrated (I will be corrected if wrong but if contradicted I WILL take another 15min off work and test it) as a motor will quite happily turn the wrong way and cetainly in the case of 2h motors they will also start backwards

yep - top cat I confirmed it, went and found a steep enough part of Nanny goat hill that when I pulled up the motor would tick over once every 13 seconds (timed) and it made no difference if I was in 1st or reverse

nuh if the clutch was stuffed it wouldnt chug coz that is tha engine turning over and a stuffed clutchwould slip between the engine and the wheels. Also if the clutch was that stuffed it wouldnt go anywhere

fraid not dozer. sure you could say i dont have enough to do at work but this post got me thinking so i thought I would give him something definite and drove out to nanny goat hill and parked my work 75 cruiser with 193k at an angle similur to the one in your rig pic high range 1st and it went noehere - didnt even look like moving

The good old 75....i will have to remember people still drive old reliables b4 i say things like that again :-0
His being t/d 80 series, the differences are gear ratio and compression.
t/d 17/1 75 -22/1
t/d 4-1 first 75 - 4.8 i think
t/d what handbrake 75 black marks
Andrew

Yea I did relize afterwards i wasnt taking 1st gear into consideration but seeing as I have a gregorys in front of me for the record the stats are
1st gear. 75 - 4.843:1, 80 series4.529:1 80 series turbo - 4.08:1
compression 1hz3628 turbo3628
dunno how much of a real world difference it makes

good effort. No wondr the compression may be down - youve worn the poor thing out BTW you never said how many ks it had