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Diesel Do · Dec 18, 2012

You're not a loony driver so I suspect a good condition standard box would be up to it! If you were a boy racer maybe not, but you aren't. You're looking for a nicer drive rather than out and out performance. so I wouldn't worry too much

WLJayne · Dec 18, 2012

Nodge68 said:
Which box was it that Rover rated at 177Ftlb? Where did you find that info?. I do know the standard High Torque box will take 250 Ftlb but you don't need that!! All you need is 170 Ftlb for a small "safety" margin. If you are happy with running a standard 1.8 turbo you might be ok. Like I said the IRD is on your side

Your engine change looks more do-able than my manual gearbox conversion but even that shouldn't be impossible.

Depends, is the magic word here.

The PG1 was never designed to take this sort of torque (I think the max spec according to powertrain was something like 177ft/lb). If you hammer the box it is possible to break it with just a standard engine. The differential bearings are prone to failure at about 90k (IME) anyway when used with a TORSEN diff, I really believe this is down to a poor design choice by Rover in moving away from the original spec taper bearings.

That said, with the exception of these diff bearings, bearing failure is pretty rare in the PG1 as they are not really a common weak point. It is debatable as to if a steel cage offers more strength. However if you are building a 300bhp engine, it would be madness (in my opinion) to put that through an unknown box without first rebuilding it and changing the bearings - they are the part that wears the most, and at least it then has a fighting chance.

I have personally put 320 ft/lb of torque through a rebuilt and steel caged NASP spec PG1 box (the weakest of the three), and run it as a daily driver for several thousand miles without any problems. But I was considerate in how I treated it (no dropping the clutch and drag style starts).

Steel caged bearing kits for the PG1 are actually (surprisingly) cheaper than the OE style polyamide or nylon cage bearings. The steel cages are more robust (although more noisy in operation) - however the cage of the bearing is not normally a highly stressed part of the bearing unless operating outside design parameters. Steel caged bearings are far more tolerant to heat though, while the OE spec plastic cages tend to be quieter in use.

In either case, when installed correctly a set of new bearings is going to offer an advantage over an old worn set, regardless of the cage material used.

Personally, if I was building a "bullet proof" box, I'd use a (preferably new) U spec box with steel caged bearings and consider machining it to fit tapers or similar for the differential. Even then you would not eliminate the chance of failure from a split housing, stripped gear or a knackered syncro.

From here: Rovertech.net • View topic - Steel Caged PG1 Gearbox Bearings and Seals

Diesel Do said:
You're not a loony driver so I suspect a good condition standard box would be up to it! If you were a boy racer maybe not, but you aren't. You're looking for a nicer drive rather than out and out performance. so I wouldn't worry too much

Yes that's why I think that the 185 map with the standard max torque would probably be ok

. Still, couldn't hurt to rebuild the gearbox anyway.

Diesel Do · Dec 18, 2012

Go the whole hog

WLJayne · Dec 18, 2012

Another interesting thread:

Standard PG1 gearbox power strain limit? - MG-Rover.org Forums

If I can get hold of a U spec PG1 then I'll get the nastiest map I can!

Diesel Do · Dec 18, 2012

WLJayne said:
Another interesting thread:

Standard PG1 gearbox power strain limit? - MG-Rover.org Forums

If I can get hold of a U spec PG1 then I'll get the nastiest map I can!

Do it

WLJayne · Dec 18, 2012

Diesel Do said:
Do it

Sure, but which one is the U spec and how the feck do I find one? Well it have the same bell housing pattern?

And can we do this:

Diesel Do · Dec 18, 2012

WLJayne said:
Sure, but which one is the U spec and how the feck do I find one? Well it have the same bell housing pattern?

And can we do this:

That'd look great with **** all over it

Diesel Do · Dec 18, 2012

WLJayne said:
Sure, but which one is the U spec and how the feck do I find one? Well it have the same bell housing pattern?

And can we do this:

You have to use the freelander bell housing cos its the only one with the IRD facility so it'll entail building a bespoke box

Nodge68 · Dec 18, 2012

Diesel Do said:
You have to use the freelander bell housing cos its the only one with the IRD facility so it'll entail building a bespoke box

Use the standard box unit a bespoke box is ready

Nodge68 · Dec 18, 2012

WLJayne said:
From here: Rovertech.net • View topic - Steel Caged PG1 Gearbox Bearings and Seals

Yes that's why I think that the 185 map with the standard max torque would probably be ok . Still, couldn't hurt to rebuild the gearbox anyway.

Power train rated the High Torque box at 177Ftlb which is why they only made an MG ZS180 and not a 190!! The 190 has 180Ftlb of torque but the 180 is bang on 177Ftlb!!

Diesel Do · Dec 18, 2012

Nodge68 said:
Power train rated the High Torque box at 177Ftlb which is why they only made an MG ZS180 and not a 190!! The 190 has 180Ftlb of torque but the 180 is bang on 177Ftlb!!

They do have to allow a bit of a safety margin to allow for owners that drive like ****s tho so a decent standard box driven enthusiastically rather than ****ishly would probably be ok!

WLJayne · Dec 18, 2012

Nodge68 said:
Power train rated the High Torque box at 177Ftlb which is why they only made an MG ZS180 and not a 190!! The 190 has 180Ftlb of torque but the 180 is bang on 177Ftlb!!

That's 240 Nm then. Yep, I think the 185 map would be better. Yes you sacrifice 5 BHP but it gets onto boost lower down than the 190 map and it's still buckets of torque.

So we'd use the FL bell housing, which gear set would I be putting in it? I think the steel cages are a must, especially if the new GB has a 80k+ mileage on it.

Nodge68 · Dec 19, 2012

Diesel Do said:
They do have to allow a bit of a safety margin to allow for owners that drive like ****s tho so a decent standard box driven enthusiastically rather than ****ishly would probably be ok!

Absolutely. Infact the High Torque gearbox will take over 250Ftlb, more if you are careful with it. The clutch will start to have problems transfering more than that anyway.

WLJayne · Dec 19, 2012

Nodge68 said:
Absolutely. Infact the High Torque gearbox will take over 250Ftlb, more if you are careful with it. The clutch will start to have problems transfering more than that anyway.

Is the difference between the HT box purely down to uprated bearing's Nodge? I can't seem to quite find a solid answer on that

.

Nodge68 · Dec 19, 2012

WLJayne said:
That's 240 Nm then. Yep, I think the 185 map would be better. Yes you sacrifice 5 BHP but it gets onto boost lower down than the 190 map and it's still buckets of torque.

So we'd use the FL bell housing, which gear set would I be putting in it? I think the steel cages are a must, especially if the new GB has a 80k+ mileage on it.

If you can limit the torque to around 160Ftlb then I'd be tempted to use the standard box making sure the correct oil is in it, maybe getting a low miler and see how that works?
If you fancy making a stronger box and keeping 4WD then you need the Flander bell housing side of the gear case as it needs to mount onto the engine and IRD. The problem comes as you need to fit the U spec output shaft along with it's different output bearings as some machining is required to fit the bearings and it's retaining plate which don't exist on the Flander bell housing!!

Nodge68 · Dec 19, 2012

WLJayne said:
Is the difference between the HT box purely down to uprated bearing's Nodge? I can't seem to quite find a solid answer on that .

No it's not that easy

the U spec box uses a different output shaft bearing set. The standard 1.8 box uses 2 ball race bearings on the outboard end of the output shaft. The U box uses 1 standard bearing and one roller bearing running directly on the output shaft. This was done to increase it's load carrying capacity. On the inboard side of the shaft they increased the bearing diameter to take more torque iirc They also added a bolt on retaining strap to hold the roller bearing in place. Iirc the output shaft is larger in diameter all over. This would mean using the U spec gear cluster to match the larger shaft. The ZS180 gear set would be a good compromise and the boxes are cheap on ebay as they are pretty hard to break which limits the market some what.
The easiest way to mod the box would be to use the bell side of the Flander box modded to fit the ZS box outer casing and whatever gears are needed for it to work. It's going to be fun.
Good luck with the upgrade

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