[Mitchie]

Hi All, worked out the final gearing for the with the intended setup of;

3SGE Beams (5th gen)
J160 6 Speed Gearbox
4.9 Transfer
3.9 Diffs
31" Tires

Engine RPM - 1000-8500
Gearbox - 1st; 3.874, 2nd; 2.175, 3rd; 1.484, 4th; 1.223, 5th; 1.000, 6th; 0.869
Transfer - High; 1.643, Low; 4.876
Diffs - 3.909

@ 100KPH in 6th Gear would be 3540RPM (vs 3350RPM on a stock sierra with 26" tires)

If I went back to WT 3.7 Diffs
@ 100KPH in 6th Gear would be 3375RPM

Or with 3.7 diffs & stock transfer
@ 100KPH in 6th Gear would be 2910RPM

What are peoples thoughts on this? This will probably end up being used as a daily & short range tourer, so would like it to be comfortable & decent fuel economy on road.

Cheers, Mitch

[Gwagensteve]

Stock transfer gearing would be the best bet. If I've found the correct specs, you have twice the input torque hitting the transfer. A stock WT transfer has the largest input gear which is the one that fails.

I also think you'd want the lowest possible cruise RPM. This is not in itself the goal, it's that you want all the other gears to be useful as well. The ratios are stacked very close in that gearbox (note 5th is direct, 1st is LOW) you're going to have a gearbox full of gears that don't do much if you run reduction.

So I'd go with 3.7's and stock transfer. 2910 is still quite high and you'll have more useful gears in the lower speed ranges.

(also taller gearing reduces torque load on the axles)

[Mitchie]

Cheers Steve, was thinking along those lines to keep stock gearing, but wasn't sure if that would be the right way to go.

[sideways]

Surely the S engines were fitted to R series gearboxes? I'd look at getting a Bundera gearbox and transfer (R151 with landcruiser split case transfer) and that would fix the highway gearing and you wouldn't break it even if you went turbo. It's also quite short to tailshaft angles and packaging are going to be easier. Down side is low range gears are expensive. This would give 2427rpm at 110 with 31s and 3.909 diffs. I think that's pretty sweet.

You could also go for a Hilux gearbox/transfer but you'd have to go to a centred rear diff.

Personally, I don't think the sierra transfer is tough enough. I think it could last but if it was my project I'd want something else in there.

[Gwagensteve]

There's no way any of the stock driveline will be strong enough, but I wasn't going down that path, just working with what Mitchie presented.

[Mitchie]

Sideways correct me if I'm wrong but the R151 has a fifth gear ratio 0.836 and would give 3100RPM at at 100KPH with stock transfer 3.9 Diffs & 31s. Also no way I'll be fitting a turbo in with this setup.

I do have a hilux R151 & transfer in the garage but don't plan to use it.

And yes I'll likely break it all, however for the transfer would you think it would be the gears or the case that breaks? Have seen the billet rear housing from LROR not cheap though.

[Gwagensteve]

Gears.

[Mitchie]

Ok so throwing ideas around that would be suitable for the power because i don't know.

What if i use an LT230 & GV Axles frount & rear narrowed to WT width & sierra hubs & cromo cv's on the front end. Yes this would be alot of work, but is just discussion to get a better understanding.

LT230 - high;1.22, low; 3.32 (low range would give about a 50% reduction over stock)
GV Diffs - 4.30/3.90

@ 100KPH in 6th Gear would be 3075RPM/2780RPM (respective diff ratios)

Cheers Mitch.

[alien]

Just out of curiosity, what has attracted you to this engine as a viable swap? Is it because you have one already and figure "why not"? or are you just trying to "do something different" ?

Or is there some other reason it has to be this motor?

[Mitchie]

Honestly don't know, i like the engine and sierra's. Wouldn't really say its a viable swap because all the issues to solve.

Really I guess its something for me to tinker with and learn more about a bit of everything that isn't work for me.

[Gwagensteve]

There's no question that's an awesome motor, but you can only ever use as much HP as you have traction. On road, I'm sure from 3rd gear up you'll be able to use all the power. Offroad, you're going to be spinning wheels, and a spinning wheel has almost no traction.

The more traction you add, or the harder you hit things, the more you're going to find the weaknesses of the sierra stuff.

An LT230 is an awesome transfer - I really rate them, but they are something like 65kg and very huge. You've already added substantial weight with the engine and gearbox. Adding a super heavy transfer is, primarily, adding traction, which means more load on the axles and diff gears. It's a complicated balance to get right. Light weight is what makes a Sierra work so well.

It might live with vitara rear based axles, although I think if the rear stays semifloat they'll be on borrowed time.

[Mitchie]

Ok, so you aware of a suitable transfer between the sierra & the landrover?

Been looking though online and the LT230 seems to be 40-45kg mark (which is still over double the sierra's) but that is with the drum brake removed which is around 20kg, so if the hand brake was on the rear axle it would save that weight.

So currently with the 3SGE & J160 all up weights about 175kg vs the stock engine and box of 93kg that's an extra 82kg.

Weights I have been able to find;

Sierra G13BA - 68kg
4age (small port) - 115kg
4age Blacktop - 130kg
3sge Beams - 136kg

Sierra 5 speed - 25kg
T50 - 29kg
J160 - 39kg
W55 - 43kg
R151 - 45kg

Sierra transfer - 17kg
Sierra transfer - 25kg (with brake & brackets, just weighed mine)
LT230 - 45kg

Also found stock dyno sheet for a 3sge Beams for reference;

[Gwagensteve]

Is there a better case? not with an indirect high range, if that's what you're looking for.

There's an additional complication here, and that's that if you want to retain the 6 speed manual, you'll need to convert any common case to divorced. This isn't too hard with an LT230, but could be a challenge with some cases. obviously the vast majority of cases with a direct high range only have around a 2:1 low range, so then you're going to have a hard car to control offroad.

Personally, if you must have a manual I would go to a R151 and a Bundera transfer case if you want to retain an offset rear diff centre. This WILL handle the power. Gearing will be fine because the transfer has a direct high range and you can run diffs in the 4.XX range and all will be well.

As I've always said, an engine conversion isn't about the engine - there's plenty of engines that meet the criteria for being suitable for a Sierra. It's the gearbox/gearing combination.

I'll leave the overall point of the conversion up to you.

If it was my motor it either wouldn't be going in a Sierra at all, or it would be going in with an auto so you can modulate the power. My experience with a 4AGE 20V in our club demonstrated to me that these very high specific output atmo motors are tricky to modulate and will require a really loose converter or they're a nightmare to control. If you gear them super low with a manual , they're easy to drive in technical terrain, but when you need wheel speed for a bump you're always in the wrong gear. However, my interest is in technical driving, not road/sand performance, so how I'd set a car up isn't like normal people.

[Mitchie]

Thanks for your advise Steve much appreciated, have you had any experience with the Datsun 720 transfer? 1:1 high & 1:2.07 low

From what i can find they have been run in the US with small block chevs & 35"+ tires without much issue.

[Gwagensteve]

I haven't worked with one, but I think they're shared with the MQ petrol auto patrol or something. I'm sure you won't be able to break it. Gearing isn't really ideal though.