ZF 8HP51 (3rd Gen) - Max Torque

[stickshifter]

Conversation moved from "Largest Functional Tire Without Mods"

This is a reply to @Tenac who wrote:
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"My performance shop that works with a transmission shop. They built my ZF in my M8 before, they called their rep with ZF there isn't a factory upgrade clutch kit like many have. The one in the Ineos stems from the same one used on the V12 7 series of old 50series but its gen3. 8HP51 which base starts at around 380-400tq numbers. There are a few aftermarket companies that can build kits but I'm not hunting that down, since there seems to be no need. However this transmission rocks 4 gear sets and 2 brakes and 3 clutch packs. ZF states this gen three is considered their heavy duty model, hence when we tried to source a higher pressure clutch packs they don't offer any they are already their higher pressure packs. Sorry I thought this stuff was well known should have considered adding a bit more detail in the first post. But basically as I build my cars and now SUV I always try to understand what potential week links there are, with automatic transmissions 100% of the time its the clutch packs which are somewhat easy swap for a good shop and you can take a limited say 500tq transmission to well over 1000tq for couple grand well add labor too."

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As most folks know, the transmission mated to the B58 (gas engine) is the ZF 8HP51 (3rd Gen). Its a great transmission, but the max torque rating on this version of the ZF 8-speed is 500 nm or 369 lb-ft of torque (I read this in a technical manual on the 8HP51, but I cannot find that now, so here is a link to the Wikipedia page which says the same: https://en.wikipedia.org/wiki/ZF_8HP_transmission). While there are aftermarket upgrades to the ZF 8HP51 that increase its torque rating (e.g. Pure - ZF 8HP 51 Stage 1 Transmission Rebuild), I have not seen any information that indicates that the stock transmission in the Grenadier has been equipped with any upgrades. I'd love to be wrong about that, but could you provide a source to your info that says that the ZF 8HP51 in the Grenadier has a higher torque rating than 500 nm (369 lb-ft). Thanks!

 

[Tenac]

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As most folks know, the transmission mated to the B58 (gas engine) is the ZF 8HP51 (3rd Gen). Its a great transmission, but the max torque rating on this version of the ZF 8-speed is 500 nm or 369 lb-ft of torque (I read this in a technical manual on the 8HP51, but I cannot find that now, so here is a link to the Wikipedia page which says the same: https://en.wikipedia.org/wiki/ZF_8HP_transmission). While there are aftermarket upgrades to the ZF 8HP51 that increase its torque rating (e.g. Pure - ZF 8HP 51 Stage 1 Transmission Rebuild), I have not seen any information that indicates that the stock transmission in the Grenadier has been equipped with any upgrades. I'd love to be wrong about that, but could you provide a source to your info that says that the ZF 8HP51 in the Grenadier has a higher torque rating than 500 nm (369 lb-ft). Thanks!

The research I've dug into so far only points that the one in the Ineos is considered "Heavy Duty Rating", which in standard fashion for the ZF is related to a higher rated clutch pack. Without tearing one down I don't know what part number is on it. When I upgraded my 8HP76 we ordered directly from ZF to take rating to over 1000. When building a Supra we ordered a clutch pack kit which also comes with the 8HP51 took the supra to about 550hp/500tq. I went the same route as last time and was told that the Ineos 8HP51 is already built to the "Heavy Duty Rating". I have no idea exactly what that was, since there wasn't part numbers or anything exchanged just that there wasn't an option. I mean they could be out right using marketing as well.

 

[Tenac]

While there are aftermarket upgrades to the ZF 8HP51 that increase its torque rating (e.g. Pure - ZF 8HP 51 Stage 1 Transmission Rebuild), I have not seen any information that indicates that the stock transmission in the Grenadier has been equipped with any upgrades. I'd love to be wrong about that, but could you provide a source to your info that says that the ZF 8HP51 in the Grenadier has a higher torque rating than 500 nm (369 lb-ft). Thanks!

The link you provided from Pure is exactly what I am trying to do with the Ineos, just with a shop I have used in the past.

 

[stickshifter]

The research I've dug into so far only points that the one in the Ineos is considered "Heavy Duty Rating", which in standard fashion for the ZF is related to a higher rated clutch pack. Without tearing one down I don't know what part number is on it. When I upgraded my 8HP76 we ordered directly from ZF to take rating to over 1000. When building a Supra we ordered a clutch pack kit which also comes with the 8HP51 took the supra to about 550hp/500tq. I went the same route as last time and was told that the Ineos 8HP51 is already built to the "Heavy Duty Rating". I have no idea exactly what that was, since there wasn't part numbers or anything exchanged just that there wasn't an option. I mean they could be out right using marketing as well.

Thanks for your reply @Tenac!

 

[Tenac]

Thanks for your reply @Tenac!

I'm with ya It would be nice to have a better understanding of what they mean by "heavy duty". It could be that it has better cooling too.... Me being new to the off road arena, I get worried about TQ limits and the amount of stress applied while offroad and the weight. If you take a look at the "limit" on the wiki and the power we are outputting right now you would be well into the 90% duty cycle for the transmission which would mean basically we are always pushing it. In my mind that means we wear it out faster. Look at the difference from the petrol V the diesel it would be better off to take that transmission HP76 and stick it on the petrol version. You can bolt it up since its mostly used in other B58 platforms as well. Just would be dumb to think Ineos stuck in a lesser transmission at a high usage without giving it some thought.

 

[stickshifter]

I'm with ya It would be nice to have a better understanding of what they mean by "heavy duty". It could be that it has better cooling too.... Me being new to the off road arena, I get worried about TQ limits and the amount of stress applied while offroad and the weight. If you take a look at the "limit" on the wiki and the power we are outputting right now you would be well into the 90% duty cycle for the transmission which would mean basically we are always pushing it. In my mind that means we wear it out faster. Look at the difference from the petrol V the diesel it would be better off to take that transmission HP76 and stick it on the petrol version. You can bolt it up since its mostly used in other B58 platforms as well. Just would be dumb to think Ineos stuck in a lesser transmission at a high usage without giving it some thought.

Yeah - in the early days, many folks were disappointed that the B58 (petrol) did not get the same transmission as the B57 (diesel). People who were talking about tuning the B58 to produce more power/torque quickly realized that a 10% increase in torque would take you right to the max rating of the ZF 8HP51. That seemed to put a damper on most talk about tuning the B58.