4BD1 exh manifold and LT85 questions.

Thanks everyone for their comments.

The vehicle the combination may be used in is one of my forward controls. I have a 4.6 V8 R380/LT230 to go in but the width of the V8 and accessibility to the LHS of the engine is giving me some concerns. Recently I may be able to acquire a 4bd1-LT85-LT230 combination at a reasonable price and this has re-aroused my contemplation.

As much as it would be nice, I'm not sure that a passenger would be too pleased to have the heat of a turbo-charger less than 300mm from their left buttock! ;)

The question yet to be asked are: what will a 4BD1 rev to? To achieve 100KPH with 9.00 16 tyres the wheels need to rotate at aprox 612.3RPM plus with the diff ratios to run at 100KPH:

1. the current series helical box and Rover 6cyl I need 4402 engine RPM
2. a regular series box and Rover 6cyl I need 3306 engine RPM
3. Using the LT85-county 1.41 LT230 I need:4057 RPM 4th or 3124 5th
4. Using the LT85-Disco 1.222 LT230 I need:3517 RPM 4th or 2708 5th

Is option 3 possible with the 4BD1?


Diana

The LT85 is a good strong gearbox. I'd happily put another one behind my 4BD1 and I did just that this year. If it lasts as long as the last one it's good for another 20 years!

Most are good for 300,000 Kms behind a NA 4BD1 before a rebuild is required - I don't think that's too bad at all given the potential damage a 4 pot 3.9 diesel can inflict via torque impulses. Many need a re-build not because there's anything wrong with the gearbox, but because they strip the splines on the output shaft. This is more of a LT230 transfer box input gear issue than a gearbox problem and is solved by fitting a cross drilled input gear, others recommend fitting splash lubrication devices as well.

My car was still fitted with the original box and did 265,000 km's before it got noisy in 5th and then another 15,000 km's before it got noisy in all gears - but it still worked to the day it was taken out and never let me down or failed catastrophically, it was just noisy. The previous owners had had no work done to the gearbox, I know this because it's only had two previous owners and I know them both.

Anyway, the main point of my post is that there are 2 versions of the LT85 - the '20C' solid case version and the '22C' lightweight divided case version. It's generally regarded that the earlier 20C solid case version is much stronger than the divided case one. I have the solid case version and I think all factory Isuzu 110's came with the solid case version, even the later 110 Isuzu's were fitted with the 20C despite the 22C being available to LRA.

Asides from the case construction the main difference between the two is that the 20C has an oil pump and pressurised lubrication delivery, the 22C doesn't and it's my understanding that it's this box behind 1000's of V8 powered landies worldwide from about 1988 to 1991 that got the LT85 a bit of a bad name.

The main complaint is that the LT85 will flog out the layshaft bearings if 5th gear if used extensively under full load... it's my understanding that this is true for the later divided case 22C which has no oil pump and suffers with lubrication issues to both the layshaft and mainshaft bearings. But not correct when discussing the 20C solid case version that does have an oil pump and thus a pressurised oil feed.

In fact - I'd like to know if anyone has got less than a quarter of a million km's out of a 20C LT85 behind a NA 4BD1, excluding military vehicles that get 'driven like it's stolen' by a gazillion different drivers. It's starting to brass me off how many people bag this gearbox and most of it seems to come from stuff they've once seen on this forum being regurgitated.

Some interesting reading from the following link: Land Rover gearbox history

1984 through 1991: The LT85 (85 mm shaft spacing) was used in all V8 110 and 90 Land Rovers. The LT85 was originally designed under contract by Land Rover for Santana in Spain and was considered to be a strong working gearbox. Rover purchased LT85 gearboxes directly from Santana. It is also known as the Spanish Box. This gearbox was used as originally designed until 1988. A cost reduced, lighter weight, divided case version of the LT85 was introduced in 1988 and used through 1991. The main short coming of the divided case version was its main and lay shaft bearings. The loading on the bearings in 5th gear caused frequent gearbox failure when cruising for long periods of time under high throttle. There was also a bearing quality problem at one stage of manufacture and the gearbox was sensitive to the type of oil used.
In 1991 the relationship between Rover and Santana ended and the LT85 was no longer available to Rover. They needed to find a quick short term solution while they developed a new stronger gearbox.

Jon

Quote:

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Originally Posted by justinc

<snip> It was always behind a NA engine and was a rare (Apparently?) 1.2:1 LT230 fitment also. He ran 8.25/16's to up the gearing for a time. <snip>
JC

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According to the original sales literature I have the 1.222 LT230 ratio was standard on the Isuzu 110 from around 1988. I think the earlier ones were 1.003?

Jon

Quote:

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Originally Posted by Lotz-A-Landies

Thanks everyone for their comments.

The vehicle the combination may be used in is one of my forward controls. I have a 4.6 V8 R380/LT230 to go in but the width of the V8 and accessibility to the LHS of the engine is giving me some concerns. Recently I may be able to acquire a 4bd1-LT85-LT230 combination at a reasonable price and this has re-aroused my contemplation.

As much as it would be nice, I'm not sure that a passenger would be too pleased to have the heat of a turbo-charger less than 300mm from their left buttock! ;)

The question yet to be asked are: what will a 4BD1 rev to? To achieve 100KPH with 9.00 16 tyres the wheels need to rotate at aprox 612.3RPM plus with the diff ratios to run at 100KPH:

1. the current series helical box and Rover 6cyl I need 4402 engine RPM
2. a regular series box and Rover 6cyl I need 3306 engine RPM
3. Using the LT85-county 1.41 LT230 I need:4057 RPM 4th or 3124 5th
4. Using the LT85-Disco 1.222 LT230 I need:3517 RPM 4th or 2708 5th

Is option 3 possible with the 4BD1?


Diana

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The governor adjustment determines max rpm. Generally the stock adjustment is from 3000 to 3600 rpm.

The screw can be adjusted if the tamper proof shroud is removed. It has been determined that they will rev to over 4000 rpm (some balanced and unbalanced 4BD1T's are revving to 5000 rpm.

For normal highway driving comfort you probably wont want to exceed about 2500 rpm.

From memory, the curves for BSFC and torque indicate best economy will be likely when the engine is running at about 1800 rpm and will be good up to about 2000 rpm.

Only knowing a little about your vehicles and use, I would be thinking of a 6 cyl diesel with a bit more displacement, gearing for no more than 2000 rpm at 100 kmh, and a drive train with strength to match.

Edit: a decent heat shield and insulation can easily take care of heat from the turbo.

Quote:

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Originally Posted by D3Jon

According to the original sales literature I have the 1.222 LT230 ratio was standard on the Isuzu 110 from around 1988. I think the earlier ones were 1.003?

Jon

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Thanks Jon - I assumed all Isuzu/County's were 1.41 transfers, but using the available 727torqueflyte ratios or the later RR/Disco ratios make sense.

Quote:

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Originally Posted by Bush65

The governor adjustment determines max rpm. Generally the stock adjustment is from 3000 to 3600 rpm.

<snip>

For normal highway driving comfort you probably wont want to exceed about 2500 rpm.

From memory, the curves for BSFC and torque indicate best economy will be likely when the engine is running at about 1800 rpm and will be good up to about 2000 rpm.

Only knowing a little about your vehicles and use, I would be thinking of a 6 cyl diesel with a bit more displacement, gearing for no more than 2000 rpm at 100 kmh, and a drive train with strength to match.

Edit: a decent heat shield and insulation can easily take care of heat from the turbo.

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Thanks Bush65

A 6cyl diesel would make sense, however this vehicle has a little history and I don't want to modify it too far so it cant be returned to OEM spec. The original engine and trans will be stored.

If you know a little of the SIIB, a turbo on the 4BD1-T would be sitting next to the equivalent of the battery box on the Defender/County possibly even touching the metal lid. Not a whole lot of room for a heat shield. :( :(

Quote:

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Originally Posted by Lotz-A-Landies

Thanks Jon - I assumed all Isuzu/County's were 1.41 transfers, but using the available 727torqueflyte ratios or the later RR/Disco ratios make sense. Thanks Bush65

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No county's have the 1.4 case, just defenders

No experience with LT85's so not much help there

What about purchasing the stuff and buying a 6BD1, that way it would be powerful enough without the turbo bum warmer? as the forward control has room for the 6, albeit a 6BD1 is larger again

Quote:

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Originally Posted by Lotz-A-Landies

If you know a little of the SIIB, a turbo on the 4BD1-T would be sitting next to the equivalent of the battery box on the Defender/County possibly even touching the metal lid. Not a whole lot of room for a heat shield. :( :(

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a nice soft turbo beanie doesnt take much room and a double wrap of header tape and heat wouldnt be that much of a problem i wouldnt think... if you can namge to get 10mm clearance...

Quote:

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Originally Posted by rovercare

No county's have the 1.4 case, just defenders

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Sorry but that's wrong. The later V8 County's were fitted with 1.411:1 transfer boxes as standard.

Jon

Quote:

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Originally Posted by rovercare

No county's have the 1.4 case, just defenders
<snip>
What about purchasing the stuff and buying a 6BD1, that way it would be powerful enough without the turbo bum warmer? as the forward control has room for the 6, albeit a 6BD1 is larger again

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I have a county LT230 with 1.41 ratio in the shed :confused:

There may be room for the Rover 6, however the LT85/LT230 is longer than the series box and there is a cross member immediately behind the handbrake drum so no room to push the transmission to the rear ruling out a 6BD1.

Quote:

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Originally Posted by Lotz-A-Landies

Morning 4BD1 people.

Can anyone of the "reliable information" people on this forum answer me a couple of specific 4BD1 engines and gearbox configuration questions.

1. Is the LT85 gearbox as bad behind a 4BD1 as some people suggest? (maybe the question should be: "Would anyone fit a 4BD1 coupled to it's original LT85 to another Land Rover model?")
2. Is there any 4BD1 exhaust manifold that doesn't direct the exhaust pipe out into the LHS mudguard that will still fit a LR chassis?

Diana

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IME:
My LT85 did 240000 km behind an NA 4BD1 in a 110 before it died (lost drive - not sure of exact fault)
It was then rebuilt by Mal Story at a cost of $4k (almost all internals replaced)
The rebuilt box now has 130000km on it. About half of that with a turbo. It has been across the nullarbor a couple of times. It has also been driven 500km with no clutch.
The synchro on 2nd started to get a little bit worn a few years ago, but I switched to Syntrans and it is now as good as the others. I regularly change down to 4th on the highway as reccomended by Mal.

Apart from the syncho issue (fixed by running Syntrans), my box seems completely fine. I expect at least another couple of hundred thousand k's from it.

My other experience is in a 110 owned by Dave S which we did an epic trip through the Americas in - again NA 4BD1 110 (Oz - built county). This one had 350000ish km on the clock, with the original LT85. 3rd gear seemed loose, and the gear lever shunted back and forth when you went on and off the accelerator (only in 3rd), but apart from that, the gearbox was fine - and 3rd gear was like that at the start of the trip, yet we spent days at a time driving in 3rd flat out (HUGE headwinds - couldn't pull 4th).

So - the bottom line is I am happy with my LT85. However if and when it dies, I will either modify the LT85 bellhousing to mate to a late R380, or fit an ISUZU box. Mainly because of the cost of rebuilding an LT85 though, not because I think it isn't strong enough.