Which Auto do i choose?

[GOTMYN]

Hi Guys/Gals,

Just after some opinions on what Trans to put into my 304 powered Patrol.
At the moment, it is running a Turbo deisel 5 speed, but I am getting over changing gears all day as I use this car for work and do plenty of Km's in a week.

The engine is a VL Black 5.0, It has a crane 286, Torker Manifold, HEI, Twin 2.5" system, running straight gas with just under 150rwkw with 33" tyres.

I am thinking a 4spd Trans would be the go, as It has 4.3 Diff Ratio.
At the moment I am sitting at 2800rpm at 100k's in 5th. I am hoping to be somewhere similar in top gear with an auto........

So the question is, which Trans do I go for?
Any help would be greatly appreciated

[wildss]

being a vl block arent you limited to a trimatic pattern?
if it was a vn block you could have used a t700

[GOTMYN]

Yeh I think you are right!!
I have just read that all VL 5.0 were Trimatic Pattern.....Not good!!

[wildss]

then your only other options are fitting a trihardmatic and changing the diff gears so you dont rev so high @100

[wildss]

or get a vn motor/trans out of the paper and fit that in

[Tom_1569]

You could get a Turbo/trimatic adapter plate, these dont have the greatest record be being awfully strong, but do work.
Not sure about patrols, But did any come out with an auto, that way you could use all standard auto gear from the patrol and hit marks 4wd adapters up for an adapter for the VL block to patrol auto.

[GOTMYN]

Yeh Ive heard that those adaptor plates are shite....
I may have to go with a beefed up Trimatic..... :-(
Anyone know the ratio of third in a trimatic?
I'd be interested to know what kind of rpm it would be at 100kmh....
I have 4.3 ratio Diff with 33" rolling diameter tyres........

[Tom_1569]

i THINK a trimatic 3rd is 1:1.

[GOTMYN]

i THINK a trimatic 3rd is 1:1.

Sweet, so 1:1 is 4300rpm with 4.3:1 diff, now to work out what the tyres do to this figure????? anyone have any idea?

[Tom_1569]

Sweet, so 1:1 is 4300rpm with 4.3:1 diff, now to work out what the tyres do to this figure????? anyone have any idea?

110km/h = 2964 RPM
100km/h = 2695 RPM

[GOTMYN]

110km/h = 2964 RPM
100km/h = 2695 RPM

Sounds good to me!!
Thanks a bunch, now time to hunt down a box

[sv9946]

arent you guys forgetting torque convertor slippage? remember the trihardmatic as someone here nicknamed it doesn't have a lock-up plate, so you'll surely loose some rpm through the convertor at 100 in top gear

[TheForgotten]

how is it that a 5speed (overdrive) does 2800 RPM, but a traumatic (no overdrive) does 2700RPM? someone stuffed something up there i think.
revs in top with traumatic - drive at 100 in 4th, that'll give you a real world result before you go messing with anything

[Tom_1569]

how is it that a 5speed (overdrive) does 2800 RPM, but a traumatic (no overdrive) does 2700RPM? someone stuffed something up there i think.
revs in top with traumatic - drive at 100 in 4th, that'll give you a real world result before you go messing with anything

Yeah, after I posted that last night I started to wonder the same thing, something doesnt add up. I may have stuffed some calculations up, Ill go over it later and check out the ratio of a 5-speed patrol box.

On a side note our Patrol does 2400 or 2500 rpm at 100km/h with 35s, but its a GU so ratios might be different again.

[Tom_1569]

Ok, Now im quite confused, so hopefully someone can check my maths. Ive done some research and the most comon diff gear ratio was 4.375, and 5th gear ratios are .91 and .84 .
33inch rolling diameter = 838.2mm - I think this is where Im stuffing up because I normally use rim size, aspect ratio and width, but that only gives me rolling diameter.

Ok so heres what I got with your current setup, using 4.375 as diff.
With a .91 over drive:
2800 RPM = 102 km/h
100 km/h = 2744 RPM
110 km/h = 3018 RPM

Thats seem pretty consistent with what you claimed.


Trimatic again:
2800 RPM = 102 km/h (thats not right)
100 km/h = 2769 RPM
110 km/h = 3046 RPM

That just doesnt seem right to me. The patrol has a small over-drive, comapred to a commy but it should still be dropping RPM by a significant amount not the 25 rpm Im calculating. As TheForgotten mentioned, run in 4th gear and it will give you an idea (most patrol 5-speed boxes have a 1:1 4th gear).

What model is your Patrol?

Im using 0% as the over drive ratio, which may becausing the confusion, im not 100% sure.

[GOTMYN]

My Patrol is an MK, there is very little difference when shifting from 4th to 5th, maybe 500rpm.....I will check it next time I drive it....

Don't forget, the normal tyre rolling diameter for a trimatic say in a commy would be somewhere around 18-19", so 33" would bring the rpm down a bit although the diff is 4.3........ wish someone had already done it so I could go fro a spin

Thanks heaps guys, really appreciate your input