ZF4HP22 to M46 conversion

[Aubergine S70]

Hi, I currently have a 760 turbo with a ZF box in it. I’ve always wanted a Manual car. I’ve read posts about a AW box to M46 but not a ZF conversion. I believe it would be pretty similar as I still have torque converter lock up. Has anyone done this? Also would I have to change the rear diff?

Thanks

[360beast]

The procedure would be the exact same and no you won't have to change the diff at all unless you find it is too high or low revving for your wants and needs.

Make sure you join the starter inhibitor wires otherwise it won't crank over.

[tofufi]

I believe the autos normally had different ratio diffs - so your conversion is likely to rev higher than the equivalent factory manual car unless you can find a diff to swap. Whether this'll trouble you may depend on how you use the car

[Laird Scooby]

Originally Posted by Aubergine S70

Hi, I currently have a 760 turbo with a ZF box in it. I’ve always wanted a Manual car. I’ve read posts about a AW box to M46 but not a ZF conversion. I believe it would be pretty similar as I still have torque converter lock up. Has anyone done this? Also would I have to change the rear diff?

Thanks

It's very unusual to have the ZF box on the back of the B230ET, do you have the overdrive lock-out button on the side of the shift lever?

Also might be worth considering the fact that you could devalue it by converting to manual, the 760 is entering collectors territory where they want it as original as possible. While some may pay a preium for an original manual turbo model, they're less likely to pay the same as an original auto value for one that's been converted.

You may be better off selling it as is and either finding a 760 T manual (original) or a 940 HPT manual, or even one that someone else has converted and get it a bit cheaper.

[360beast]

Originally Posted by Laird Scooby

It's very unusual to have the ZF box on the back of the B230ET, do you have the overdrive lock-out button on the side of the shift lever?

Also might be worth considering the fact that you could devalue it by converting to manual, the 760 is entering collectors territory where they want it as original as possible. While some may pay a preium for an original manual turbo model, they're less likely to pay the same as an original auto value for one that's been converted.

You may be better off selling it as is and either finding a 760 T manual (original) or a 940 HPT manual, or even one that someone else has converted and get it a bit cheaper.

The first 2 760 turbos I broke had ZF boxes Dave, my mates 1987 760 turbo also has a ZF box so I'd say it is uncommon to have an AW on a 760 turbo. I'm yet to check out what is on my 1990 760 turbo automatic but I'm expecting it to be an AW at that age.

The trouble would be finding a manual 760 turbo as according to the website how many left there are only 67 760 turbo manuals left and only 13 of those are on the road. My manual 760 turbo is incredibly rusty and doesn't run yet I will go the extra mile to get it back on the road due to how rare it is.

According to that website there are over 400 760 V6 left and about 200 turbos left interestingly, so that means just over a quarter of them that are left are manual.

[Laird Scooby]

Originally Posted by 360beast

The first 2 760 turbos I broke had ZF boxes Dave, my mates 1987 760 turbo also has a ZF box so I'd say it is uncommon to have an AW on a 760 turbo. I'm yet to check out what is on my 1990 760 turbo automatic but I'm expecting it to be an AW at that age.

The trouble would be finding a manual 760 turbo as according to the website how many left there are only 67 760 turbo manuals left and only 13 of those are on the road. My manual 760 turbo is incredibly rusty and doesn't run yet I will go the extra mile to get it back on the road due to how rare it is.

According to that website there are over 400 760 V6 left and about 200 turbos left interestingly, so that means just over a quarter of them that are left are manual.

That's interesting stuff Luke, all the 760 turbos i've seen have been facelift (1988 on) and AW boxes, maybe that was a general thing and the ZFs were fitted to earlier models?

I was looking the other day on howmanyleft and i can't remember the exact figures but for 1988, there are only about 60 ish 760 V6 left, about 40 are SORN so mine is one of the 20 ish still on the road. When i first got it, there were less than 400 760s left so it seems a few have come out of hibernation, people have moved (and generated a new style log book/V5 and become "known" to the Continuous Registration system that gives SORN or taxed status) or have been "barn finds" and returned to the road.

What proportion of those 760s are V6, Turbo or diseasel i couldn't say but it doesn't leave many at all when spread across a population of 55-60 million people!

I'm fairly certain the 760 V6 was never offered with manual transmission in this country (although i believe other markets did)

[360beast]

Originally Posted by Laird Scooby

That's interesting stuff Luke, all the 760 turbos i've seen have been facelift (1988 on) and AW boxes, maybe that was a general thing and the ZFs were fitted to earlier models?

I was looking the other day on howmanyleft and i can't remember the exact figures but for 1988, there are only about 60 ish 760 V6 left, about 40 are SORN so mine is one of the 20 ish still on the road. When i first got it, there were less than 400 760s left so it seems a few have come out of hibernation, people have moved (and generated a new style log book/V5 and become "known" to the Continuous Registration system that gives SORN or taxed status) or have been "barn finds" and returned to the road.

What proportion of those 760s are V6, Turbo or diseasel i couldn't say but it doesn't leave many at all when spread across a population of 55-60 million people!

I'm fairly certain the 760 V6 was never offered with manual transmission in this country (although i believe other markets did)

The first two were 1987 and 1988 which makes me think it was just the V6 and potentially the very last 760 turbos offered with the AW, I was just by my 1990 760 and completely forgot to look at the Vin!

Well as long as I've got my 760 turbo manual that's enough for me haha. The 1990 will be for sale once it has been welded etc and is back on the road.

[Aubergine S70]

Thanks for the information and replies very helpful. The reason I asked about. Manual conversion is that I’m having to problems at the moment and can figure out what it is I’m suspicious about the gearbox. Over the past couple of months I’ve been doing some work, when I replaced the rear rubber gearbox mount I noticed a whine coming from the gearbox in 1. This whine got louder when accelerating and went when Changed into 2nd. It also returned when changing down into 1st. I suspected the propshaft support bearing, the bearing did have a lot of play and was dry so I had the prop professionally rebuilt with new bearing and balanced. Now the problem I have is that there’s still the whine but now I have a very annoying sort of drumming vibration coming through the car at 60MPH. It’s a sort of a rotational vibration coming through the car but not the steering. However when I put the car in neutral the noise and vibration go, soon as I go back into drive the drumming starts again. I’ve changed the gearbox filter and fluid since and the 1st gear whine is quieter but still drumming. I was suspicious about the torque converter as I’ve know on other cars I’ve had vibrating when revved on tick over. I know these gearboxes are prone to issues of not looked after but it changes very smooth and no slipping. If anyone could help it would be great.
Thanks

[Laird Scooby]

Originally Posted by Aubergine S70

Thanks for the information and replies very helpful. The reason I asked about. Manual conversion is that I’m having to problems at the moment and can figure out what it is I’m suspicious about the gearbox. Over the past couple of months I’ve been doing some work, when I replaced the rear rubber gearbox mount I noticed a whine coming from the gearbox in 1. This whine got louder when accelerating and went when Changed into 2nd. It also returned when changing down into 1st. I suspected the propshaft support bearing, the bearing did have a lot of play and was dry so I had the prop professionally rebuilt with new bearing and balanced. Now the problem I have is that there’s still the whine but now I have a very annoying sort of drumming vibration coming through the car at 60MPH. It’s a sort of a rotational vibration coming through the car but not the steering. However when I put the car in neutral the noise and vibration go, soon as I go back into drive the drumming starts again. I’ve changed the gearbox filter and fluid since and the 1st gear whine is quieter but still drumming. I was suspicious about the torque converter as I’ve know on other cars I’ve had vibrating when revved on tick over. I know these gearboxes are prone to issues of not looked after but it changes very smooth and no slipping. If anyone could help it would be great.
Thanks

Sounds very much like the prop centre bearing is in the wrong place. Could be a couple of other things too but i'll get to those in a mo.

Firstly, crawl underneath and loosen the prop centre bearing brack bolts by 1/2 a turn. If, like me, you're not quite skinny enough to crawl under to do this, reverse it onto a pair of ramps - DO NOT JACK!!!!!

Take it for a short test drive, accelerating and braking gently, return home and then crawl under (or put it on ramps again then crawl under) and tighten each bolt in turn a small amount at a time evenly in sequence until they're all tight. Test drive to see if the vibration has gone, if so it's all good. If it is worse (unlikely but possible) then note the speed at which the vibration happens now and repeat the above, getting up to that speed with the bolts half a turn loose.

If this doesn't improve the vibration, there are more things to check. First, rear suspension height and whether the rear suspension is working correctly. Depending on what year yours is, you will either have a solid live axle rear set up or post 88, you will have the multilink IRS set up.
If it's the live axle then check your Nivos (dampers) for leaks. If they are leaking or sagging (you'll find the back end sinks when the car is parked), they need renewing - easiest way is to replace the rear springs with normal rear springs and dampers. Also inspect the various bushes on/around the axle that locate it, wear in these can cause the vibration as well.

Next, although less common on the ZF than the AW is the extension housing oil seal and bush. Easy enough to renew on the AW at least and fairly sure the ZF is basically the same.



That's a worn extension housing bush in an AW ^^^^^ and after renewal with the old components held for comparison :



Note there are oilway holes in the housing and also in the bush, these should line up. Twenty minutes between the two pics above so it's not a long job.

There could still be other causes but those are the most likely. Out of curiosity, what ATF did you use when you changed the fluid?