Best diff ratio??

[kpwemu]

Hi All, I am soon to remove the 302 Windsor and single rail 4 speed from my 1960 Mk2 Zephyr ute and install a 1UZ and auto. I am currently running a 3 :1 LSD Ford 9 inch diff. This works fine, revving at 2500 at 100kph with 70 profile tyres on 14 inch wheels. I want to continue with the 14 inch wheels as I have a mint set of wire spoke wheels and spinners with will look trick on the Zephyr. After reading many threads on this forum, I am still unsure which is the best overall diff ratio, considering the over drive. I feel that if I stick to the 3:1 diff ratio, the motor will be hardly ticking over at 100kph and will have bugger all acceleration. I don't want to get rid of the diff centre as I spent heaps having it recoed. I thought that changing the gear ratio may be the way to go. There seems to be varying opinions as to what revs are best suited to the 1UZ. The ute will be a Club car (mainly ZZOCM Club outings) rather than a daily driver and therefore economy isn't most important. I dont like to hammer my cars either. I am looking for suggestions as to the type of revs (diff ratio, considering wheel and tyre size) my 1UZ needs to produce to get good torque without screaming its face off, yet giving reasonable fuel economy.
In summary, what is the best rev range to get torque, without destroying economy, and what diff ratio is required to do it? Remember:
14 inch wheels
70 profile tyres
For comparitive purposes, 16 inch wheels with 50 profile tyres are the same height. I tested this with a spirit level.
Regards. Kevin

 

[krayn]

Im running 16 inch rims with 225 55 16 tyres. With the stock a341e trans the rpm at 100km/h is aprox 2200. The acceleration is not too bad with the 3.7 ratio diff, better than the 3.08 ratio. I use mine on the road but want to build it mainly for draging. If I had my time again I would go for 4.11 rato diff as it still bogs down at take off. Probably with a 2500 rpm stall converter it would be better. If at stand still I nail it there is slight wheel spin for about 10 meters and then hooks up.

 

[doey]

If you wan't to drive any distance and keep reasonable fuel economy, I'd use 3.5's

If you never leave town try the 3.7's.

 

[Zuffen]

You can't discuss diff ratios without involving the tyres rolling circumfrence so you know how many revs per kilometre or mile the axle will make/

From there you need to decide how many revs you want the engine to do.

Factor in the overdrive and the diff ratio is the answer.

All simple easy calculations.

Don''t guess get out you pencil and calculator.

If you want a hand PM me with the rolling circumfrence, required revs and overdrive factor and I'll let you know the diff ratio. The ratio I come up with is a mathamatical calculation that may not be available in your make of diff. But it will allow you to decide the closest diff for your applicaion.

 

[deankdx]

Yeah simple to work out once you know what revs you want at 100km/h
eg: 2500rpm X 0.7(overdrive)= 1750, had near this and its pretty slow taking off an overdrive labours a little at 100kmh

now for diff ratio swap, 1750(result with overdrive) divide current diff 3.1 multiply by 3.7(diff i would go for if keeping auto, i have 3.45 little tall still) = 2100 at 100kmh although i reckon it would be higher than this as i reckon that your 2500@ 100 is a little low?(might be big tyres? misleading me) i think the take off would be fairly good. Kris has the HG ute and it wheelspins a bit, MY falcon had LSD 3.45 and did not wheelspin at all on take off but i think this is QUICK still, probably 3.9 will still be good on highway,
these motors(well mine at least) seem like they are doing less revs than they actually are, when you are sitting on 2500, it wont seem as if it is when compared to a windsor/clevland etc from my experience.

when i fit the Manual, i think i have a W57 which has a 0.85 5th?, i reckon will be doing near 2500 at 100 with the 3.45 diff ratio economy will still be good in my opinion, providing i can resist the temtation to race it

are you going with the L300 front end Kevin?

 

[Zuffen]

It's simple to work out what a change in dif ratio will do but a lot of people need to start from scratch.

When you do a swap into any vehicle you need to calculate the effect considering the diff ratio and tyre size.

A lot of people do a swap into a car they have never driven, perhaps because they built the car rather than just doing an engine swap into a known vehicle.

 

[kpwemu]

L300 Front end

Hi Dean, L300 front end looks like the way to go. Cheap, proven on heaps of cars as being good quality, engineers don't have any issues with them, they are axle rated to carry big weights being from a commercial vehicle, will allow me to cut out shocker towers that take up space in the Zepyhr engine bay if necessary giving extra witdth to fit the motor, they already have the same stud pattern as Ford, Hopper's Stoppers can do a big brake upgrade, a Commodore power steering rack bolts straight on, even though it is 10cm wider than the Zephyr, I can overcome this by using different offset wheels. If desperate, the engineer said that he had no problems if it was narrowed ( cut & shut ) providing it was done properly. As you can see, there are lots of good reasons to go with the L300. What makes it better is that I have a buyer lined up to take all the Zephyr front end, struts, brakes etc etc. They are flat out down at Hoppers at the moment so nothing is likely to happen until Feb / March next year. At least I've got the Cortina to play with for now. I'll keep you posted. Kevin

 

[kpwemu]

Info to calculate diff ratio

Hi Zuffen, I have the info you require to calculate the diff ratio I would require. The rolling circumference 1932 mm. According to another thread on this site, the 1UZ runs most efficiently at 2,600 rpm and I believe the overdrive ratio that I would get from the standard Crown auto is 0.71. I also read on another thread that at 2,500 revs on the 1UZ you can hardly notice it. Seeing that they redline at 6,500 you would think that they would be comfortable at 2,500. I hope that this will help you calculate the required ratio. In summary
Rolling Circ = 1932mm
Required revs = 2,600
Overdirve ratio = 0.71
Regards, Kevin

 

[Zuffen]

I have the program at work on my work computer.

I'll run the numbers tomorrow for you.

 

[Zuffen]

KPWEMU,

I ran the numbers for you and a 4.26 diff is the exact number you want.

If you moved to a 4.2 diff your revs drop to 2572 and if you went up to 4.3 they rise to 2634.

I have a simple Excel spreadsheet that works it out for me.

 

[kpwemu]

4.11 might be best

Hi Zuffen, Thanks for the info. Having a Ford 9 inch diff under the ute,based on your calculation, 4.11 gears may be the way to go. They are easy to find and should brings the revs down to about 2,550 which is close enough. The Windsor and 4 speed that I had in it used to rev at 2,500 at 100klm with 3.0 :1 gears and sounded comfortable so the 1UZ would be in heaven at those revs. Many thanks, Kevin

 

[Zuffen]

4.11 will give you 2517rpm @ 100kmh. But if you shift back out of overdrive you'll jump to 3546rpm which should have the car percolating nicely.