gear ratios for acceleration

[Wambat]

hey guys, if you wanted to get faster acceleration, you would go higher in diff gears (ie from 4.11s to 5.11s) i dunno if 5.11s exist, i am just using it as an example.

say for instance on a 60 series, running 36 - 37 inch tyres, and you want as quick as possible acceleration, car would have no need to drive at 100ks an hour, so high rpm not so important.


or is there another way to achieve this??

[sprungupcruiser]

Yep pretty much, lower differ gears will help with acceleration. I'm guessing 4.56:1 would bring it back fairly close to standard with 37's on, then there is 4.8 and 5.29 if you want to go lower again, they are available for cruisers and hilux's, not sure on other makes and models though.

[ISUZUROVER]

Yes - either lower diff gears or lower (high range?) transfer gears - assuming you have a t-case which allows you to change high range ratios.

The other thing that helps is reducing rotating mass. I.e. wheels and tyres as light as possible.

[Wambat]

5.29 sounds good, are there any lower??? or would i be getting into custom gear territory there??


i dunno how you would make 36 -37s light as possible, the vehicle will be for a specific event, where acceleration is alot more important, and the whole event would be done in high range, transfer case would be getting quite pricey though wouldnt it??

[sprungupcruiser]

I'm going to be running 37's on my bj73, I'll be running standard diff ratio's with a marlin crawler toybox, however most of my comps will be low range stuff. If you are going to be doing higher speed stuff then diff ratios are probably your best option. You can buy 5.29's of the shelf, but you will find yourself grabing 2nd gear very quick. It all depends on what suits you really. What engine are you running?

[dogbreath_48]

It is important to have appropriate driveline ratios, but when it comes to acceleration there's no substitute for horsepower.

[Wambat]

the event isnt high speed, more like a motor cross circuit, turns jumps a couple of hills (man made so they are more like a big bump)

the important part is to be able to come out of turns andd punch it and get speed quickly before the next turn, i dont think ya would see 80 ks an hour, maybe as i havent driven yet, but i saw enough, and navied for one run, annd it wasnt the fastest thing i have seen.

what motor i run depends on what i buy, i have two options, use my 75, and buy a street car, or buy a 60 series and use my 75 to tow it (but we shouldnt need to tow we have access to a truck to get it to the event.

ino matter what i am going to try my hardest to stick a 12ht into it. as for the event the water is the killer. alot of the 4wds i saw competing competitively in open class were petrol v8s, and most of them at some point through the day had issues caused buy the water getting into the electronics, and we noticed that if you were consistant rather than fast all day you had a good chance of getting to the top 4. so a turbo diesel (a couple turbo diesel gqs were there and they were very competitive to the v8s) with lower ratios should be a good mix, specially if we start tinkering with the turbo to get it to spool up lower.

[sprungupcruiser]

Righto, well I guess if you made the 60 as light as possible, worked the 12ht and had lower diff gears then it could work quite well, I don't know if i'd go to 5.29's though, I think 4.88 would be enough.

[ISUZUROVER]

the event isnt high speed, more like a motor cross circuit, turns jumps a couple of hills (man made so they are more like a big bump)

the important part is to be able to come out of turns andd punch it and get speed quickly before the next turn, i dont think ya would see 80 ks an hour, maybe as i havent driven yet, but i saw enough, and navied for one run, annd it wasnt the fastest thing i have seen.

what motor i run depends on what i buy, i have two options, use my 75, and buy a street car, or buy a 60 series and use my 75 to tow it (but we shouldnt need to tow we have access to a truck to get it to the event.

ino matter what i am going to try my hardest to stick a 12ht into it. as for the event the water is the killer. alot of the 4wds i saw competing competitively in open class were petrol v8s, and most of them at some point through the day had issues caused buy the water getting into the electronics, and we noticed that if you were consistant rather than fast all day you had a good chance of getting to the top 4. so a turbo diesel (a couple turbo diesel gqs were there and they were very competitive to the v8s) with lower ratios should be a good mix, specially if we start tinkering with the turbo to get it to spool up lower.

If you are taking jumps at any speed I would want coils.

I would buy a cheap 80s or 110.

T-case gears (or whole t-cases) are dirt cheap for rovers. Factory options range from ~1:1 to ~1.6:1. NFI about toyota?

If you are buying tyres, comp tyres like irocs are often quite a bit lighter. You can also remove tread blocks to save weight. Alloys are often lighter than steels etc...

[Wambat]

isus rover thats some good advise. thanks

on the cars that were there though, there were quite a few on leafs and alot of them done really well. so coils are not necessary, and i cant pick up anything id want to use for under 5 grand with coils.

also one of the classes is what you can pick up for 1500 or under, so if you were aiming to compete in that class, you would be lucky to find anything on coils(there were a few rovers but they didnt run well and the water killed most of them)

i want a diesel 80 as a tow truck not a comp vehicle lol....

there was a 60 in each class, a petty 6 in the under 1500 class, he done quite well. except when it got a bit to wet.
a 12ht sahara in standard class, he done really really well, came 3rd of 4th, with no work done i think he was on alterains too.
and a 351 or 302 powered 60 in open, he did quite well oon the jumps too, but sliped his slip joint out on the front, and i think that was the end of him on the day.

and as i am a fan of the 60 and seeing how they done i am inclined to run one,

this isnt an event where you need to spend 20 gs, its more about getting out there and having a go, so for the 3 or 4 times i compete id like to do it in something cheaper to get a feel for compeating in this event,

[1MadEngineer]

6.1 is available (old school)

[ISUZUROVER]

isus rover thats some good advise. thanks

on the cars that were there though, there were quite a few on leafs and alot of them done really well. so coils are not necessary, and i cant pick up anything id want to use for under 5 grand with coils.

also one of the classes is what you can pick up for 1500 or under, so if you were aiming to compete in that class, you would be lucky to find anything on coils(there were a few rovers but they didnt run well and the water killed most of them)

i want a diesel 80 as a tow truck not a comp vehicle lol....

there was a 60 in each class, a petty 6 in the under 1500 class, he done quite well. except when it got a bit to wet.
a 12ht sahara in standard class, he done really really well, came 3rd of 4th, with no work done i think he was on alterains too.
and a 351 or 302 powered 60 in open, he did quite well oon the jumps too, but sliped his slip joint out on the front, and i think that was the end of him on the day.

and as i am a fan of the 60 and seeing how they done i am inclined to run one,

this isnt an event where you need to spend 20 gs, its more about getting out there and having a go, so for the 3 or 4 times i compete id like to do it in something cheaper to get a feel for compeating in this event,

In that case I would pick up a 110 county V8 (1984-1990). You could pick one up for <$1500 if you look around. There are plenty of options for waterproofing the ignition. You could swap the wagon body for a ute cab and get it down to ~1500kg easily - which would save a lot of weight. You may be lucky enough to find one converted from a 3.5 to a 3.9, 4.4 or holden/chev V8.

[GUtripper]

Yep pretty much, lower differ gears will help with acceleration. I'm guessing 4.56:1 would bring it back fairly close to standard with 37's on, then there is 4.8 and 5.29 if you want to go lower again, they are available for cruisers and hilux's, not sure on other makes and models though.

Remember though the lower (higher) you go in diff ratios, the smaller the pinion gear, and typically the weaker it is.
Just something to remember if running big tyres and giving the drivetrain hell.

[KiwiBacon]

It is important to have appropriate driveline ratios, but when it comes to acceleration there's no substitute for horsepower.

Eggsactly.
Diff ratios can at the most just split gear ratios. Because once your diff ratio has changed enough to move a whole gear, you've just gained or lost one at either end.

[RED60]

I think the super low gearing is B/S to some degree... you need a good spread that suits the course.... just because you have low gears doesn't necessarily mean it will accelerate more quickly... as an easy test... time your vehicle over 20, 50 and say 100 metres in low range and high range... see what the stopwatch says... while I realise this isn't exactly the same as lower diff gearing it may give you something to consider...

[dogbreath_48]

In the same vein as red60's idea above, with super low ratios and a diesel you'll probably just find yourself changing gears the entire time, rather than actually getting anywhere. The v8 county idea is a pretty good one if you ask me.

[Wambat]

thanks for the tips guys, i guess near standard gearing would be most appropriate. as i need it to be strong and if i would be sacrificing strength, i dont want to do it. but i dont want to go for a petrol v8, and i dont want to go for a rover or coils. if i wanted a v8 on coils id go a gq with a 5 litre.


i just like leaf sprung cars. and i know 60 series, and i like steel (correct me if i am wrong but the 110 is alloy yeah??)

i dont want to be chasing my tial playing with something i know nothing about on race day.

[ANDREWGQ 351]

Sounds like your talking about mud racing, id definatly go a V8 with a worked auto and then try it with std diff ratios, just let the auto pick the best gear, or manually shift, manual gear box would be to slow. Plus the added clutch work your leg would need to do. Waterproofing should be no problem as long as you dont park above the spark plug level

[-Scott-]

i just like leaf sprung cars. and i know 60 series, and i like steel (correct me if i am wrong but the 110 is alloy yeah??)

Aluminium body panels (lighter ), steel chassis.

As others have said, if your gearing is too low you'll spend all your time changing gears.

Turbo diesel sounds like a good option, as long as you get enough flexibility out of it. If there's not enough rev-range from where boost comes in to redline, you still may not get the result you want.

Perversely, something with big tyres and crappy (i.e. not really low) low range may work well if you end up doing all your running between 3rd & 4th gear in low range? Personally, I find 2-3 gearshift (in a standard H) to be slower than 1-2 or 3-4, and I'd hate to be forever changing up & down between those two.

Or go an auto, and don't worry.

[Wambat]

its not mud racing, its quite similar, but not the same even though some of the cars were still using tractor tyres, its a longer track than the mud drags i saw, and the hills and moguls werent in the mud drags i saw.

the event organizers say its more like motor cross.

yeah i see the light on not playing to dramatically with diff ratios. from what my mate said most of the track your lucky to get out of second gear. so if your motor is powerful enough you can start in 2nd and then ustalise third, like my old 12ht used to be like, i could move of at a decent pace in 2nd on the road.

in my 75, the 1 -2 gear shift is the slowest, with 3-4 and 4 -5 being fastest, 2 - 3 isnt to bad, but it feels very similar to my old 60 too, if running in low range would you be starting in 3???

[ISUZUROVER]

if running in low range would you be starting in 3???

Probably not if you are running standard gearing and 37's!

This is a very useful ratio calculator to work out how fast you can go for a given gearing setup:
http://www.ashcroft-transmissions.co.uk ... _calc.html" onclick="window.open(this.href);return false;
(it is a landy-based calculator - but just select "other" for all and input your ratios manually)

Will you be able to find a turbo'd 60s for a reasonable price? An na diesel would be a waste of time.

What you are describing is not too different from OBC style driving - just shorter courses and a smaller budget... Have a look at what is competitive at the OBC.

[coxy321]

I'd probably look at a small diff ratio change, but i really think an auto would definately outweight your gains with shorter ratios, as with the shorter ratios you'll be swapping gears more often=time wasted.

[ISUZUROVER]

I'd probably look at a small diff ratio change, but i really think an auto would definately outweight your gains with shorter ratios, as with the shorter ratios you'll be swapping gears more often=time wasted.

Agree - waterproofed V8 with auto would be the quickest and cheapest combo. And what do the most competitive OBC vehicles run these days?

[Wambat]

an auto would definitely be worth is, but again cost to make it work, in the long run though after a few years of playing it would be sweet. but within the next 12months i dont think so for my self personally.

and you guys are right, a v8 auto would be a great combination, and as i havent looked at obc yet, i understand that your saying thats what they run,

im not looking to be competitive yet, just consistent, and i do like to be different, just cause 15 out of the 20 competitors in the event run petrol v8s, i would want to run something else.

60s with a 12ht depending on condition of the whole lot can range heaps in price, seen a couple for 10 grand, and i knew of one a couple years ago for 4 with a goot motor and a slipping auto. so its all about keeping your eyes and ears open, and having the cash to pounce when something good comes up. which i never do lol.... a 2h would be ok in the bushmans class but not open, open it would just be too slow. but a 12ht could hold its own i think. 2h turbo may be an optiion, one which i will explore if i use my 75 instead of a 60, up side being my 75 is already a ute, and is registered so i can run in standard class, but if i wanted to tow my 75 or a 60 for that matter i would need a new fourby to tow with, i would love it if i could tow a 60 with my 75 but i dont think the 75 would be able to once you add a trailer and 60 weights together. plus the 2h in the 75 would blow a foof foof valve...

so at this point in time, most of my information gathering is just research untill i work out how i am getting said play thing to the event and back, if were getting a truck to take it and a mates car then ill buy a cheap nasty beaten up old 60 diesel and fuck with that in bushmans for a little while, then work it over a few years of experience later