Goes like stink now

[Gazzar]

Yes, and it's a solution.

 

But they are sooooo long compared with a series box. And there so much space at the bell housing doing nothing. How long is the input pinion shaft? Compare with a fwd car?

It's silly, I know, but I think that there's a better way, keeping the transfer box and engine in the same place.

[Anderzander]

Does that only leave making a shorter input shaft and custom bellhousing? 
 

 

[Snagger]

11 hours ago, Gazzar said:

Sure, but it would be nice if there was a neater, simpler, stronger, serieser alternative.

I plan on doing exactly what you suggest on one of my dreaming builds, so I agree with you. But....

Overdrives aren’t risky if they’re inspected/fixed before installation and the (Fairey) splines are good.  If you’re worried, you could keep the standard input gear and rear bearing carrier in a box in the vehicle to prevent being stranded - it’d take half an hour to swap back at most.  As long as you ensure the oil level is right (dipstick on the Fairey, automatic on the Roverdrive as long as the transfer box level is good), then you won’t have any problem.

I know somebody who has a complete Fairey, bought to be a little project in its own right and already seen by you, if you decide to go that way.😉

[Gazzar]

No, I've a couple in storage that I can rebuild in time, thanks, though.

I suppose my point is that both approaches are compromises. One requires moving engine or transfer box, and the other adds yet another level of complexity.

I must have another look at my stumpy R380, I wonder if you could make an even narrower bell housing.....

 

[Snagger]

The ratio of 5th gear on an LT77 or R380 varies with suffix, but I believe all are significantly lower than the 1.28:1 that fourth with overdrive gives on the Series system.  That’ll still leave you under geared, and the boxes, while more robust and less weepy than the LT76, are harder to work on and a fair bit more complex, plus you have the hassle of chassis and floor/tunnel alterations.  Moving the engine forward can also cause clearance issues with the front diff under major axle articulation.  Moving the transmission means custom prop shafts and more messing about with mountings and brackets, the hand brake links and speedo cable length.

Replacing the entire transmission and diffs will give a great gearing range, but needs custom props, even more mods to the floor and tunnel, and the issue of mismatched speedo head and drive system.

I have been content with the standard SIII set up plus overdrive, though it’s still a little low geared for motorways.  I think an LT77 on Series transfer box and diffs would be a waste of time, as it’d be lower geared still.  I’d say go with a simple overdrive or bite the bullet and go for the whole Defender transmission, including diffs. 

[Gazzar]

This is my point. Get/ design a box that fits dimensionally between the flywheel and the transfer box. That has the gear stick where God intended. That has a decent over drive top. And a lower first. 

No moving anything. 

Elegant. Sympathetic. Expensive.

 

 

 

[Snagger]

How about the Series transmission, with overdrive, SII suffix B low range (about 17% lower than all the following units) and 9.00 tyres (roughly 10% rise in gearing) of the 4:1 ish gears like I’m going to fit, which are also around 17% taller than 4.71s?

[Gazzar]

Oh, sure, all good options, period, appropriate and all that lovely stuff.

I have recently acquired a pair of 3.9 diffs from a Santana, so that's an option that I can explore if I come across another pair of old 10 spline true tracs some day.

I just get jealous of the 6 speed fwd boxes that you can get in modern cars.

A lower 1st and a really high 6th would be lovely behind a TDI.  

[Cornish Rattler]

On 7/7/2021 at 12:58 AM, Chicken Drumstick said:

I put 3.54 diffs in my Tdi Series III.

Swings & roundabouts on the pros and cons.

Cruising rpm is lower and you'll be able to cruise at higher speeds. I even clocked mine at 92mph (GPS) on the level (non public highway). And sitting at 60-70mph is certainly doable, if a bit lot noisy.

Downsides, 1st gear is quite a bit taller to pull away in. You will notice it when trying to whip out at junctions or cross a lane of a busy bypass, forcing you to slip the clutch a little more than ideal. If towing this is exaggerated. 30mph is a PITA as 4th gear is just slightly too tall unless on level or downhill grades. But 3rd will feel like you are revving the engine high. Basically there is a bit of a gap between 3rd and 4th ratios and the 3.54 diffs exaggerate this.

But most of all I found the vehicle less fun and less peppy on the 3.:54 diffs. When touring & laning in Wales with the standard 4.75 diffs, 3rd gear was lovely on twisty Welsh lanes. With the Tdi you could steer it on the throttle and drift round some of the corners. Had huge fun chasing down a herd of Lotus Elises in the wet around the Elan Valley. I'm sure they could have gone quicker than me if they really tried. But I think they were surprised to see an old Series Land Rover catch them up! With the 3.54 diffs the gear is just a bit too tall to be able to do this. And 2nd would be way too low.

I also found the low 1st crawl speed was far to quick for my licking on technical off road obstacles with the 3.54 diffs.

Had I kept the vehicle I planned on going back to 4.75 diffs and an Overdrive.

 

That's the problem I have with the 3.54's in 1st is just to high which makes normally pulling away in 2nd even harder so have to use 1st then when I have the trailer on or towing something 1st is a bit sketchy and then 4th is to low without an o/d so my thinking is if I was to fit 3.9:1 diffs 1st would be a lot lower and probably wouldn't need to use it unless I was towing so 2nd would be ideal for pulling away then if I fit a Roamadrive 4th would be a lot better