Transmission ratios - custom setup: V8 & R380 into Series

[twodoorgaz]

Hi folks - looking for a bit of advice here. I'm getting closer to starting assembly on my next build - last one was focused on the quality of the restoration (museum piece and totally stock but boring to drive and a bit fragile), this one is keeping the shabby bodywork and all effort is going into the divetrain. I write, surrounded by cardboard boxes from Ashcroft and other suppliers.

But I'm massively confused with the ratios to choose for the donor diff/R380 before they go for recon. Not so much final drive, more whether the gaps between 1st-4th will be appropriate for a V8 (aiming for a factory feel)

Into a SWB 1969 Series IIA is being stuffed the following:

 

• BOUGHT: Rover V8 plus Gems front cover (have a 4.6 for MS but its a bit much for the clutch so still toying with a traditional-looking 3.5 on clockwork SUs with MJ)
• YET TO BUY: 9.5" 130 (HD) TDI clutch 
• BOUGHT: Milner Philips series V8 adaptor and engine mounts
• YET TO BUY: A R380 (Defender, Suffix L) - not yet bought the donor box (will be going straight to Ashcrofts)
• BOUGHT: Stumpy R380 conversion kit (bell housing, clutch fork/parts and Suffix L input pinion which will be turned-down to fit spigot)
• BOUGHT: Ashcroft to Series transfer box adaptor
• BOUGHT: Series IIA transfer box (have a suffix C but can change to the earlier suffix B)
• BOUGHT: 24 spline shafts to go in rear axle
• YET TO BUY: rear diff (ratio TBC), will be rebuild with ATB and 24-spline (nice little touch - a PowerLok LSD was a rare factory option in 1969)
• BOUGHT: 235/85/R16s
• BOUGHT: standard rear prop (will be shortened)
• YET TO BUY: skinny Disco V8 front prop for addl. clearance over bell housing crossmember (will be lengthened)
• YET TO BUY: chassis (standard Richards but with a 2nd set of bolt-up crossmember mounts 102mm further back). All above bolts straight in.
• TBC: steering. Have all the bits for a P38/Defender setup. If I go for a powerful engine I'll go P38 for feel, and will have the brackets put on the chassis, if I use a 3.5V8 aim for traditional+, then I'll stick with stock.

 

Things I have no choice about:

• 44A Suffix L main gearbox - the 050A (petrol) parts are NLA so I have to have it rebuilt to 44A (300TDI) spec.
• 235/85/R16 tyres.

Things I can change:

• 5th Gear - I can have Ashcroft build it with either the standard (0.77:1) or higher (0.73:1) V8 5th ratio
• Series transfer box - I can use the pre-1967 suffix B or post- Suffix C gearing here
• Diffs - I can have the diffs built to series (4.7) or coiler (3.54) ratios.

 

Now final drive ratios are easy (4th is 1:1 in all boxes, 5th can be picked to give the best cruising RPM).

The problem I have is 1st-3rd. I've been in a 200TDI/Zeus-bellhousing LT95 RRC and it was horrible - the gaps in the gearing did not suit the TDi at all. Fine once you got in top though.

I'm doing something similar in reverse - a V8 onto a Diesel box and am terrified that the ratios will be ill-suited to the V8.

Example 1:

With the 44A R380, 1969 transfer box, standard diffs and 31.7" (235) tyres I get the following:

High Table

Speed/Gear	First	Second	Third	Fourth	Fifth
10 MPH	2113	1220	800	572	441
20 MPH	4227	2441	1599	1145	882
30 MPH	6340	3661	2399	1717	1322
40 MPH	8454	4882	3199	2290	1763
50 MPH	10567	6102	3998	2862	2204
60 MPH	12680	7322	4798	3435	2645
70 MPH	14794	8543	5598	4007	3085
80 MPH	16907	9763	6397	4579	3526

Example 2:

With the 44A R380, 1969 transfer box, coiler diffs and 31.7" (235) tyres I get the following:

High Table

Speed/Gear	First	Second	Third	Fourth	Fifth
10 MPH	1592	919	602	431	332
20 MPH	3184	1838	1205	862	664
30 MPH	4775	2758	1807	1293	996
40 MPH	6367	3677	2409	1725	1328
50 MPH	7959	4596	3012	2156	1660
60 MPH	9551	5515	3614	2587	1992
70 MPH	11142	6434	4216	3018	2324
80 MPH	12734	7354	4818	3449	2656

Example 3:

With the 44A R380 with V8 5th, 1969 transfer box, standard diffs and 31.7" (235) tyres I get the same 1st-4th as example 1 but with the following in 5th:

Fifth
10 MPH					419
20 MPH					838
30 MPH					1257
40 MPH					1676
50 MPH					2095
60 MPH					2514
70 MPH					2933
80 MPH					3352

Example 4:

With the 44A R380 with V8 5th, 1969 transfer box, coiler diffs and 31.7" (235) tyres I get the same 1st-4th as example 2 but with the following in 5th:

 

High Table

Speed/Gear					Fifth
10 MPH					316
20 MPH					631
30 MPH					947
40 MPH					1262
50 MPH					1578
60 MPH					1894
70 MPH					2209
80 MPH					2525

 

Any advice would be very, very welcome. I can use the Ashcroft Ratio Calculator (see here) but I'm not great on interpreting the results.

Edited March 4, 2017 by twodoorgaz

[Daan]

I'd say 3k revs at 70 is about right for a v8, certainly not higher revs, so example 3 would be my choice. But on paper it is hard to judge. Why are you stuck with the series transfer box?

 

Daan

[twodoorgaz]

Thank you Daan, I'll take that on board.

I appreciate the Series transfer box is always a bone of contention - most people go LT230 and understandably baulk at the cost of the adaptor. I've seen and driven both but prefer the physical fit of the Ashcroft-Series adaptor - no need to scallop the bell housing crossmember or use prop spacers, no concerns re: handbrake drum clearance, less reduction in rear prop length and its more than strong enough for anything a RV8 can throw at it. I simply have Richards include a 2nd pair of bolt-up gearbox crossmember mounts 102mm further back and it slots in beautifully. in the future, if I want to refit the original box, 10-mins with a grinder to knock the extra mounts off and the chassis is back to factory (plus no issues re the "topic that shall not be referenced" on this forum).

Downside is silly, silly cost of the kit, a much noisier transfer box than the (even) stronger LT230 and no option to move to permanent 4x4 (shame as I already have stage 1 CVs for strength over stock UJs).

Very much a personal choice, that's difficult to explain, but 'feels' right for the project (traditional '60s/'70s V8 conversion and only injecting modernity where essential to give the system the strength it would need to have been sold by the factory). I'm leaning away from the 4.6 V8 and P38 steering I bought and onto a 3.5/stock steering for the same reason.

MJ is another example - by adding this and the Disco gems timing cover I gain a little extra space at the front which was another issue back in the day that couldn't be solved with period technology. Once fitted I'll be tweaking the front panel - adding a custom brass radiator to give the cooling it needs but (if I can avoid going over the front crossmember) retaining the SIIA wide top tank. I have wild ambitions of finding a way to fit a fixed fan (rather than viscous) to the serpentine pulley - probably overly ambitious, but I'll cross that bridge when the engine is in place.

MJ, Gems Serpentine front cover and R380 mainbox are the modern prices I have to pay to make a traditional conversion perfect.

 

 

 

Edited March 4, 2017 by twodoorgaz

[twodoorgaz]

PS Daan - your truck was actually the inspiration for the wheels.

I always have one-ton rims on my builds, so I bought 6.5J 130 wheels. But for safety I really wanted tubeless (have run tubes in tubeless tyres in the past and never felt great about it). I'll be running BFG Muds (closes thing I can find with a decent speed rating but with high shoulders like factory cross plies).

After reading about the wheels on your hybrid I contacted a company down south who are going to band a set of late defender 5.5j tubeless steels to replicate my 130s but tubeless.

Cost is amazing (well, free), I bought my rims cheap so the profit from the resale value is more than enough to buy and modify the defender rims.

Edited March 4, 2017 by twodoorgaz

[Daan]

Good to hear you read my thread. Daan

[FridgeFreezer]

OK running through a few of your comments...

1. Which V8 are you fitting? If it's a 3.9+ (you mention 4.6) then you have all the torque in the world and don't need to worry about ratios other than 1st for low off-road control and 5th for relaxed cruising. The middle ones are interchangeable once you're moving, you could just whack it in 4th and go everywhere. Unlike a TDi you don't need to keep the V8 "on boost", it's got a much wider useful range.

2. Why worry about the clutch? Buy a standard one, your left leg will thank you. Both my 4.6's run std. clutches (with the alloy release bearings, mind) and they have never had a problem. Given that one is a 127 Ambulance it does work harder than many - and we've driven it over a fair few mountain passes!

3. For the choice of ratios etc. what are you using the truck for (off-road toy, overland, towing, doing many miles, etc.)? No point building a relaxed motorway cruiser to go trialling in!

4. Diff ratio choice: 3.54's may leave you over-geared off-road for low speed control, I found that in my 109 originally when I had 3.9 V8 + series box + 3.54 diffs. Mind you, at the top end, even with the overdrive, it was still under geared on the motorway!

5. Depending on diff ratios / tyre size, if you have a larger V8 go for the highest 5th you can for lazy cruising. Mind you, a Series transfer box leaves you the option of an overdrive... a Fairey unit may not thank you for 200+hp though and WILL make you deaf.

3000rpm is quite high for 70mph with a V8. Again, our 127 ambulance (which makes a std. Defender look sleek and aerodynamic) feels under-geared on the motorway with a V8 R380 + 1.4:1 LT230 behind the 4.6, so much so that I'm seriously considering a Roverdrive if we do any more long trips in it.

[twodoorgaz]

Thanks very much for the detailed reply FF. re: your queries:

1: I have a 4.6 already which was my original 1st choice nice find as the seller included an int. serp timing cover . I've also given some thought to swapping it for a 3.5 - looks nice on original carbs and definitely won't stress the 9.5" clutch (your points on the clutch noted).

2: clutch - I've heard of 9.5" clutches (which I'm limited to due to the stumpy R380) starting to slip on higher torque motors. LR always fitted their V8s with 10.5" clutches. Are your 4.6s on 4-cylinder gearboxes or ones with V8 bell housings?

3: Its an all-rounder. Some off road work, mainly on road. I've had both D90s and Discos in the past and note they have slightly different gearing - for this application one that drives like a disco would be ideal (slightly higher ratio). I don't yet have an R380 mainbox so options are 4-cyl 300TDi/TD5 or V8 Disco (assuming the stumpy input pinion I have is compatible).

4: useful to know re: the diffs. I'm leaning towards 4.7s with the 5th gear on the R380 taking the place of a Fairey OD on the original box. I don't need to improve low-speed crawling, but not willing to sacrifice it too much in exchange for higher cruising. With 3.54s this gives 2209RPM@70mph - possibly a bit low and with 4.7s, 2933rpm which is possibly a bit high.

5: regardless of which R380 I go for, I'll definitely be having the V8 5th (ashcrofts can include it on any build). Tyres will almost certainly be 235/85R16s.

 

aah decisions, decisions - last thing to buy is the mainbox.

[Bowie69]

Sounds like 4.1 diff's are your ideal?

Would put the gearing almost exactly at what an RRC/disco is.

[Snagger]

3.54 diffs will be horribly overgeared, while 4.71 will be undergeared (R380 5th will be lower than 4th with overdrive, too).  4.1 or thereabouts would be much better, and I am trying to find some for my 109 (Tdi with Series transmission and OD, tried on 4.71 and 3.54 diffs).  If you do go for the 4.1s, it'll up the ratios about the same amount as a SII suffix B low range gear set drops compared to C and later, so I'd recommend that combination.  At least the Rover diff 4.1s (and 3.9s) are easy to source and not outrageuosly expensive - not so Salisbury diff gears.

[FridgeFreezer]

On the clutch, high torque diesels are abusive to the drivetrain as there's 4 big thwacks of lumpy rattly torque, V8's tend to be kinder as you get it in 8 smaller lumps - HALF the impact! It's partly why modern diesels have dual-mass flywheels, to take the big spikes out. I ran an injected 3.9 on a Series 6cyl clutch & gbox and it went OK. Both my 4.6's are on OE V8 clutch, bellhousing and R380's. I realise you don't have so much space in an SWB but a serp-fronted 4.6 might give you enough clearance up front for a V8 bellhousing - you can make a lot of room at the front of a Series if you chop the cowling off the back of the rad panel.

This is the engine bay in the 109, the rad is flat against the back of the grille (zero cowling) with electric fans (which could be slimmer), serp front end, you can see there's miles of space to move it forward - being a 109 I chose to keep it further back for weight distribution because I could.

[twodoorgaz]

Thanks all very much indeed! Think I'm sorted now and thought I'd update this thread with the conclusions.

You were quite right - there's not a lot in real-orld terms between the TDi/5 and V8 boxes when you run the numbers.

Basically it turns out that, when run through a Series transfer and standard series 4.7 diffs, a TD5 defender box can give almost identical ratios as a standard SIII box, and the same 5th as series 4th+OD. If you throw in 4.1 diffs and the optional V8 5th gear (offered as an option by the Ashcrofts and the like) then you get close to factory defender V8 gearing too.

The defender TD5 R380 box is commonly available - and is compatible with the stumpy pinion/bellhousing - and comes in suffix K (bigger bearings) and suffix L (bigger bearings and shot peined components) flavours which is  massive bonus.

(he says… hopefully I've got the following right)

 

Responding to the above posts: Fridge - yep, regardless of whether I stick with the 4.6 or switch back to the 3.5 I'll be keeping a skinny GEMS front cover (coilpack either way for waterproofing).

The timing case I have is actually one from a disco II which points the oil filter forward 45-degrees the same as a RRC and makes for a better take-off for the remote oil filter (P38 is points straight down out of the side of the timing case). Bolt-on with the 4.6, or a bit of work on the crank for fitting the shallow timing case if I stick with 3.5, but no great issues there.

That photo is incredibly useful - it shows the clearance to be actually better than I thought it would be as I'd like to stick with an engine fan and like you, my rad will sit on the crossmember, so should be bags of space. Also your comments on the clutch have calmed my nerves a bit re: strength and it is no longer a factor in deciding between the two engines (just comes down to heart vs. head - or carbs + MJ vs MS).

The aim is to build a Series V8 conversion of old, but with a bombproof alternative to the 4-speed + overdrive.

Had a really good chat with a potential gearbox builder today and have come up with a formula, turns out a standard Defender TD5 box is almost bang on the money.

 

Here's the comparison:

Defender TD5 R380 + 1967-onwards series transfer + 4.7 diffs + 30.7" tyres (235/85/R16s).

For comparison, in a traditional conversion - Series III gearbox and transfer box + Fairey Overdrive + 4.7 diffs + 30.7" tyres (235/85/R16s).

 

You'll see that on the TD5 combo 1st is very slightly lower than the SIII box (but nowhere near as low as the SIII one ton) - no bad thing when pulling away with a trailer and 1st low will be great crawler. I rarely use 1st in a standard SWB Series anyway as it a bit low for road use.  

2nd and 3rd are virtually identical.

4th is identical (1:1)

and 5th is almost identical to a SIII in overdrive top.

 

Now the R380, being a 5-speed offers a bit more flexibility as during the recon the 5th gear can be changed to an even higher unit (V8 spec) for more relaxed cruising, this gives the best of both worlds - slightly lower 1st and slightly higher 5th, but still balanced nicely across the range.

Defender TD5 R380 PLUS V8 5TH GEAR + 1967-onwards series transfer + 4.7 diffs + 30.7" tyres (235/85/R16s).

 

This is the setup I'm going for. Rather than try for super-high gearing in 5th to make it cruise like a Disco, if I stick with the above it should give a nice vehicle to drive - with very similar (but fractionally more usable) ratios as a traditional Series V8 conversion.

Also a bit easier/cheaper as I only need to source one more component - a Def TD5 Suffix L mainbox. I already have everything else.

 

Thanks again everyone - massively appreciated.

Edited March 14, 2017 by twodoorgaz

[twodoorgaz]

PS: for interest, if I did add 4.1 diffs to the equation then taking the above setup (Defender TD5 R380 PLUS V8 5TH GEAR + 1967-onwards series transfer + 4.7 diffs + 30.7" tyres (235/85/R16s)) but swapping the diffs to 4.1...

would give me very similar gearing to a late, manual NAS D90. Have to do a bit of research on availability of 4.1 diff parts.

NAS Defender 90 - R380

 

Defender TD5 R380 PLUS V8 5TH GEAR + 1967-onwards series transfer + 4.1 diffs + 30.7" tyres (235/85/R16s)

 

 

 

Edited March 14, 2017 by twodoorgaz

[Bowie69]

Ashcroft supply 4.1s.

[Snagger]

I just bought this http://www.ebay.com/itm/DANA-60-RING-PINION-4-10-1-WITH-YOKE-1310-CHEVY-DODGE-FORD-/191565094186?_trksid=p2141725.m3641.l6368 for my rear Salisbury.  Shame I sold the 3.54 centre it needs to be fitted on!  The idea is to (eventually) try it out on the back end, and if it makes the difference I hope, get a matching set for the front.  I think you will find the same results as I had - 471 too low and 354 too high.  You can do this, or you could go with 3.54s and an LT230, the latter being much cheaper and technically better (quieter, stock parts, less leaks), and if you copy Ed Parrot's method, you retain a completely standard cab, including the red and yellow levers (he's a blooming genius, but don't tell him!).

[Jamie_grieve]

Santana PS 10 will give you the option of 3.9 diffs in wider axles. The spring perches are different widths though and don't just bolt up. Keeps leafs, adds disc brakes, all standard Land Rover bearings and seals inside.

 

[Snagger]

As I understood it, the PS10 had a reputation for blowing rear diffs.  I have no idea what type of diff they had, but I knew someone who had several rear diff failures on PS10s at his off road training school.  If you want wider axles with discs, then doing the Defender/RRC/Disco axle route would be easier to source for initial work and for later servicing, and if I could do it successfully, then most others could.

Getting 4.1, 4.11 or 4.12 Rover diffs (Ashcroft do 4.12, Kam do 4.1) is not the hard bit.  It's finding the Salisbury gears.  Both companies seem to have done them in the past but not now - they are shown in the Kam site diff gear section, but not on the shopping section, suggesting they stopped making them, though it could be a software glitch.  They were pretty expensive, though.  Dana 60 gear sets are very common in the US, with plenty of aftermarket manufacturers from $200-450.  The snag is that the vast majority have differently splined pinions, so won't fit the Rover pinion flanges.  You could buy a yolk that fits the UJ, as they tend to have three different UJ yolk sizes for the D60, but they seem to cost about $80. 

There is an additional expense with the 4.1 diffs; you need 3.54 diff centres to fit the gears to - the ring gear flange on the 4.71 centres is too close to the pinion axis to allow for the thicker crown wheel and larger diameter pinion head.  I would like to fit an ATB while I'm at it (has to be Eaton as Quaife and Ashcroft don't make Sals ATBs).  Maybe you could use it as an excuse?