8HP Transmission Swap

[john erbe]

Heard about this conversion which is gaining some popularity. Haven't seen it done into a vintage Mercedes but looks promising for added value to my 6.9 eventual sale.

 

[ProfessorExperimental]

I advise extreme caution.

If your goal is to add value for sale, consider that, at least imo, the only proven "market" for w116s in general and 6.9s in particular is collectors/afficionados/enthusiasts *of vintage mercedes*. There may be buyers who like to tinker, have their own mechanical/performance goals and ideas or are otherwise wonky in the head enough to think a Panzer would do well with 53° of opposite lock wound on hammering out of a turn with smoke peeling off its (lowered, locked) rear end (and of these wierdos I hereby stake my claim as king, or at least "minor aristocrat with aspirations to the throne")... but these buyers don't want an 8hp preswapped into a 6.9. They probably don't even want the headache of a real 6.9, since an m119 swap or worse (LS? Barra? *gasp* something bmw?) will get them the go and they need something haltech-shaped to run the 8hp anyway. So they'd be more in the market for a 280/350 rolling shell in good condition, at been-on-gumtree-ages-need-gone-asap prices, since they'd want to do that 8hp swap themselves, conning themselves they can do it cheaper and better than you did. They certainly wont pay what such a swap will end up costing or more as a price premium to you. Again, hi, I'm Mark. Meet my car, and all the adventures I've had getting it to start and (briefly) run.

Look at the Motorex 2026 thread, there is one photo of a white Torana I think with an army green turbo six and exhaust pipe out the bonnet. (Engine is a barra, BTW, and the turbo size suggests "roll racing" or "dyno shootout"). The builder loves the 8hp swap, and did a lot to popularise it here. Lurking in the background of that shot I see Jason "Keep It Reet" Fearron's (sp.?) drift car "Barrawags" (R31 skyline wagon with a barra and also, iirc, 8hp). These are the sort of guys who froff over an 8hp swap. I very much doub5 they are your ideal 6.9 buyers.

By all means do the swap if you want a stout gearbox in your car, it'll give you many years of enjoyment, cope with the 6.9 torque and, if you program your tcu appropriately offer the true cake-having-while-eating experience of manual-like shifting or auto-like cruising on the fly. But it won't sell your car for much more than even a regular 450se(l) 3 spd would. Certainly less than the cost of the swap more, and maybe even nothing more.

 

[abl567]

I advise extreme caution.

If your goal is to add value for sale, consider that, at least imo, the only proven "market" for w116s in general and 6.9s in particular is collectors/afficionados/enthusiasts *of vintage mercedes*. There may be buyers who like to tinker, have their own mechanical/performance goals and ideas or are otherwise wonky in the head enough to think a Panzer would do well with 53° of opposite lock wound on hammering out of a turn with smoke peeling off its (lowered, locked) rear end (and of these wierdos I hereby stake my claim as king, or at least "minor aristocrat with aspirations to the throne")... but these buyers don't want an 8hp preswapped into a 6.9. They probably don't even want the headache of a real 6.9, since an m119 swap or worse (LS? Barra? *gasp* something bmw?) will get them the go and they need something haltech-shaped to run the 8hp anyway. So they'd be more in the market for a 280/350 rolling shell in good condition, at been-on-gumtree-ages-need-gone-asap prices, since they'd want to do that 8hp swap themselves, conning themselves they can do it cheaper and better than you did. They certainly wont pay what such a swap will end up costing or more as a price premium to you. Again, hi, I'm Mark. Meet my car, and all the adventures I've had getting it to start and (briefly) run.

Look at the Motorex 2026 thread, there is one photo of a white Torana I think with an army green turbo six and exhaust pipe out the bonnet. (Engine is a barra, BTW, and the turbo size suggests "roll racing" or "dyno shootout"). The builder loves the 8hp swap, and did a lot to popularise it here. Lurking in the background of that shot I see Jason "Keep It Reet" Fearnes' (sp.?) drift car "Barrawags" (R31 skyline wagon with a barra and also, iirc, 8hp). These are the sort of guys who froff over an 8hp swap. I very much doub5 they are your ideal 6.9 buyers.

By all means do the swap if you want a stout gearbox in your car, it'll give you many years of enjoyment, cope with the 6.9 torque and, if you program your tcu appropriately offer the true cake-having-while-eating experience of manual-like shifting or auto-like cruising on the fly. But it won't sell your car for much more than even a regular 450se(l) 3 spd would. Certainly less than the cost of the swap more, and maybe even nothing more.

"Torana I think with an army green turbo six and exhaust pipe out the bonnet"
If it's the sky blue one I think you're talking about that's a Benz diesel engine, OM616 I think

And what is a 8hp?

 

[ProfessorExperimental]

Ah OK I stand corrected.

My point was "that guy likes to Frankenstein and mod and chase the youtube clicks", so... even more so than I realised I guess!

 

[john erbe]

Been away from forum. In answer to question, what is an 8HP? It's the ZF 8 speed automatic transmission. Comes in several variants. Found in Bentleys, BMW, Dodge Chargers to name a few. By pure chance was tipped off about conversion by guy who was going to put the 6.9 M100 into a 280 with the BMW version of the 8HP.

 

[Styria]

Hi Professor, what an interesting little thread that you have started - or was it John Erbe. I think it was John , but your response was somewhat more comprehensive. You raise some valid points. One of them certainly touches upon 'original' versus 'modified'. On the one hand, if you have the stickler that won't even spare a look at a modified car, insists on Australian Compliance which DOES NOT render it a better car when compared with a grey import and, when all said and done, it is the preference exercised by the buyer of a much "treasured" and desirable 6.9, who exercises the criteria for choosing the car that suits them best.
I will give you my point of view, if you haven't read it elsewhere on the forum. I have modified, my 6.9 fairly conservatively. First of all, I have changed the color from the original "Taxi White" to MB877 Petrol. A somewhat Greenie/Blue that, whilst not original from factory, it is far more striking to the eye. So, does original specification come into this and therefore render the Taxi White more desirable ? In my opinion, the answer is an emphatic 'No". However, I have committed a 'sin' in having it painted in a two tone color scheme. In this instance, with the lower half being a home grown mid grey (say charcoal) I concede that originality in this instance can rear its controversial opinion. If that is a sticking point to a prospective purchaser, that can be rectified on the proviso that the car is good enough otherwise condition and the bottom half can be matched to the top color MB877.
From a mechanical point of view, I have changed the exhaust system from standard factory specification. A differently shaped (very shallow and quite wide 350SL first muffler), together with a huge best quality SS muffler straight through, with the system providing better economy and and a much more authoritative sound accompanied by a noticeable gain in power. That's the way it feels. Morte importantly, and significantly so, the system has been split into three sections that are coupled together by readily removable flange fitting to assist in a number of mechanical solutions that otherwise would prove the bane of a long and very heavy one p[iece original factory system. To my mind, there is no contest between original and modified especially in this instance given the fact that the end muffler can be unbolted readily in minutes and fit in its place an end muffler that will quieten the sound. More to come. Regards Styria
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[Styria]

Talk about Mechanicals, and that's where we stradle the fitment of a modern Automatic box such as the ZF 8 speed. BTW, in this instance completely forget a manual box no matter how much it might appeal to some. As you may be aware, the standard three speeder provides 105 km/h, 170 km/h and probably a theoretical 250 km/h in top. In my opinion, those ratios provides the driver with everything he needs for town or open road use, except save for one shortcoming or drawback. More of that later. Admittedly, first could be a bit shorter if you want to burn off, or at least keep pace, with the modern hot shots. However, keep in mind not the power, but torque of that M100 engine. I have now seen two 6.9s with barely functioning input shafts with splines that have almost down to being almost non-existent. All caused by "tramping" on the loud pedal to beat the guy next to you, or just for sheer pleasure of exploring the power and acceleration of that M100 engine. I am not into that. The long arm of the law can rear its ugly head without you knowing where it is coming from.
Once on the move, and if you are up to say 50 kms or 60, and if you pull back to 2nd gear, believe me all hell will break loose but, in the interests of points and monetary considerations, the better option is to ease off. You will have proved your point. Just try it once if you get the opportunity.
No, the principal shortcoming of the 6.9 relates to open road cruising. In standard factory specs., top gear equates to 40kms in top gear at 1000 rpm., so therefore 120 (keep fingers crossed) equates to 3000 rpm - IMHO that engine speed is far too high. Admittedly, with the high compression engine and maximum torque 3K. rpm, the car will really just amble along, and immediately ready for increasing your speed. Okay overseas, but not OZ country.
Compare those cruising ratios with my Holden Captiva - at a100 km/h, the engine turns over at 2100 rpm and it will cruise all day at that speed. So, what I would like to see is a taller ratio in the 6.9 differential. Would it not be great to cruise at 110- and have the engine turning over at 2000 ? Absolutely fantastic. Better fuel economy, less strain on engine, I mean I would be in heaven. I am not sure, but a diff ratio of 2.3 or 2.4 would make an appreciable difference to fuel economy. A diff from a 126 - 500 may provide at least a partial solution. The ZF 8 - no, not for a 6.9. Regards Styria

 

[Styria]

To conclude, I am a great believer in certain modifications, and if a prospective purchaser would be put off, I believe in letting sleeping dogs lie. You can't change their opinion, no matter what.
On the other hand, a well maintained and well cared for 6.9, with the 8.8 :1 high compression engine, better economy, improved fuel consumption, fewer under bonnet AD complications, regulations, makes it compelling to look beyond the not so obvious. Regards Styria

 

[ProfessorExperimental]

I'm with you Styria. Probably even more so if I owned a 6.9 but even for the 4.5 that'll eventually live in my car I came to the conclusion that the 3 spd will do (after a *lot* of trans swap research since the chewed up ring gear Problem #1 had me doing gearbox googling before anything else). For historical reference I note that the 450SL rally cars also ended up with (manualised) factory 3 speeds instead of any true manual boxes, although they had options aplenty.

My main point hinged on John saying straight off that he hoped the 8HP swap would "add value for eventual sale".

I disagree with that, but I'd happily put one in my w116-that-i-never-intend-to-sell if I couldn't refurbish or use (either of) my 3-spd trans (bearing in mind for me that's much less likely than it might be for a 6.9 owner, given the rarity of the heavy-duty boxes). And if I had the money. And the time. Both would be better applied elsewhere on my car, for sure!

 

[Styria]

Hi NAB, you've put it in a nutshell - if you spend big bucks on a ZF, you'd want the car to give you the opportunity and satisfaction that only you have something different to what everyone else is likely not to have. Also, let's be honest, it would make good conversation - if nothing else, plus bragging rights. I am not ashamed to include this last one. In trailbike and Motocross riding speak, you call that 'bench racing" with a coldie in your hand and almost too buggered to talk. Regards Styria