ZF 8 SPEED TRANSMISSION CONVERSION CONSIDERATIONS

[FellowTraveler]

Jay the CPA brought up an idea that may see reality sooner than later it's sparked my interest for sure. Let's see if we can get more realistic information for such a conversion.

I start with;

ZF 8 SPEED TRANSMISSION VERSIONS FOR 6.5TD CONVERSION CONSIDERATION

8HP45/845RE 500 ft. lb. torque capacity,

8HP70 700 ft. lb. torque capacity,

8HP75 750 ft. lb. torque capacity,

8HP90 1k torque capacity

Adapting these transmissions to a 6.5TD may not be too troublesome because some are used in Dodge V6, V8 and diesel applications.

With double overdrive it’s unlikely you need to change current gear ratio (s).

 

[THEFERMANATOR]

What is your reasoning for this? 8th gear is not much taller than 4th in a 4L80E, so the only advantage I could see would be the 4.71 1st gear. The other issue you would run into would be gearing. If you have a 4X4, the lowest you can now go with a 9.25" IFS is 3.42, so after spending all the money to adapt over to it, you would still only be capable of the same hwy MPG as is available with a 4L80E. You would do better towing since you would have that deep 1st gear, but thats about it. The 8 speed trans came about to help engines with a narrow power band, and to take better advantage of rear gears like 3.08:1.

 

[FellowTraveler]

What is your reasoning for this? 8th gear is not much taller than 4th in a 4L80E, so the only advantage I could see would be the 4.71 1st gear. The other issue you would run into would be gearing. If you have a 4X4, the lowest you can now go with a 9.25" IFS is 3.42, so after spending all the money to adapt over to it, you would still only be capable of the same hwy MPG as is available with a 4L80E. You would do better towing since you would have that deep 1st gear, but thats about it. The 8 speed trans came about to help engines with a narrow power band, and to take better advantage of rear gears like 3.08:1.

OK, FERM I like your response as a reality check!

 

[JayTheCPA]

What is your reasoning for this?

Unless I am missing something, a bunch of items.

While the final is close to the 4L80E, with 3.73's I'd rather highway cruise with a final gear in the .6 range, so the 8HP's final gear of 0.667 or 0.64 is close enough and ends the hunt for a gear splitter. And at 70 MPH, the 6.5 is just plane loud, so dropping several hundred RPM's will likely not affect the motor much but will definitely improve relationships with the right-seat driver

For towing, I'd rather have a gear in the 0.8 range as I tend to drive at 55 mph for a bunch of different factors. With the 4L80E, direct (3'rd) is too low, and OD (4'th) is too tall. For motors with the ATT (and a 3.73 rear), 0.8 at 55 mph is right around the sweet spot where the turbo comes to life, so in this case it will keep the turbo humming and easily master minor hills without either bogging or needing a lower gear.

Given the above two items, I would not touch my rear or front diff to re-gear them.

Climb performance while towing. With the extra gear ranges, it eliminates need for a gear splitter.

The 8HP looks like it is fully capable of tow-haul.

The 8HP's specs states better internal efficiency (am presuming this means lower parasitic drag) than earlier generations of ZF trannies. Implicitly this puts it in a better place over the Allison 1000 and 4L80E.

At 198 lbs (am presuming dry), it is heavier than the NV4500, yet lighter than the 4L80E, Allison, and ZF6 manual.

For climbing and descending grades while towing, having a lighter tranny (than the 4L80E) with extra gears and tow-haul capability is a win-win-win to me. Eliminating the need for a gear splitter is icing on the cake.

Naturally all-in cost is a factor, but from a spec standpoint, the 8HP looks like an excellent alternative to the 4L80E.


Aside, supposedly GM's new 8L80E is better than the 8HP on paper, but time will tell whether it is equal or more robust than the ZF. Also, am not aware that anybody came up with a stand-alone controller to retrofit the 6L80E into the GMT400 system, so it is questionable whether this would ever happen for the current GM tranny either.

 

[FellowTraveler]

How many psi is that ATT blowing in od at cruise"

There is a standalone computer for the 6L80/90e so not much of an issue for conversion, cutting, moving the t-case back and relocation of drive shafts is a must too.

The ZF controller is internal and only 4 wires outside it's obvious one is pos and another is neg. but what do the other two attach to? How about bell housing or t-case adapter or would a Dodge Cummins ZF w/t-case bolt in?

 

[JayTheCPA]

How many psi is that ATT blowing in od at cruise?

4 - 6 at 70 mph.

The ZF controller is internal and only 4 wires outside it's obvious one is pos and another is neg. but what do the other two attach to?

Given only two wires are leftover, am purely speculating that they are for talking over the network with the ECM/BCM. Definitely need a better expert to confirm.

 

[THEFERMANATOR]

A 4l80e weighs about 150 pounds. I just don't see the point in it. It's like guys doing the 6 speed conversion to the allison in early trucks, there is little to no gain, except your lighter in the wallet. You could do a gear swap for a fraction of the cost of the zf swap, and be right in the rpm ranges you listed with 3.73's and the 8 speed. And even the 4l80e can have a tow/haul type mode with the right controller. I know many see the wow factor, but in reality thats about where it would end as this kind of swap would never pay for itself to 99% of the drivers out there. It's like my BURB, yeah it's got wow factor, but isn't all that practical in reality.

 

[GM Guy]

Once I found out you guys were talking about automatics, I lost interest.

I wish one of the trans makers would make a heavy 7 speed manual. But then the mfg.ers would put a junk clutch and/or flywheel in it, and make it suck.

 

[THEFERMANATOR]

Once I found out you guys were talking about automatics, I lost interest.

I wish one of the trans makers would make a heavy 7 speed manual. But then the mfg.ers would put a junk clutch and/or flywheel in it, and make it suck.

Some of us just can't row gears no more, so we has to run the slushboxes. My right shoulder and left hip would not be happy if I had to row gears on a daily basis anymore.

 

[JayTheCPA]

A 4l80e weighs about 150 pounds. I just don't see the point in it. . . . And even the 4l80e can have a tow/haul type mode with the right controller. I know many see the wow factor, . . . but isn't all that practical in reality.

Good to know that the 4L80E is a lot lighter than the 254# specs I found. From what I found on specs, that also makes it lighter than a NV4500 . . . (?)

Seeing as I never was a 'wow' factor kind of guy, 'wow' is not a factor and merits / performance are. Comparison of the specs is appealing given that the 8HP is likely more internally efficient than the 4L80E and eliminates interest in a gear splitter. So, better internal efficiency = more power to the wheels and less fuel to do it. Getting more range in the gears is a bonus. If the 8HP is more durable than the 4L80E when adding towing to the mix, that makes it an outright win.

Definitely agree that jumping into an 8HP is not the best idea unless somebody wants to do it just for fun. Planning for an 8HP as part of an overhaul path when the 4L80E dies does make sense. Naturally this presumes it works without major modification and has a nearly equal (or better) cost over the expected life span. Currently, lack of a bell housing and controller make the 8HP just a mere discussion topic at this point.

As for me, I'm not interested in rehabbing the 4L80E to make it tow-haul capable, especially after reading WW's commentary about it. I am going to convert over to a manual which is tow-haul capable right out of the crate Only outstanding question is whether it will have 5 or 6 gears.

Some of us just can't row gears no more, so we has to run the slushboxes.

Completely understand and respect that.

Seeing as I can row, I want out of the slush box as it is too much work to make it work right

 

[JayTheCPA]

I wish one of the trans makers would make a heavy 7 speed manual. But then the mfg.ers would put a junk clutch and/or flywheel in it, and make it suck.

That is the most plausible reason why the consumers are getting the slush box jammed on us. Auto makers are just not spec'ing the tranny to handle any load and 'selling' the slushbox as the better alternative which also gets better mileage. Toward the better mileage aspect, this is starting to come out as bunk due to gearing differences and not the 'technology advancements' per marketing literature.

EPA compliance is likely another factor. But to me this indicates a lack of commitment to the product as am confident that software can easily handle emissions with a manual tranny.

 

[FellowTraveler]

Actually, people have converted from NV 4500 to Road Ranger manual which gets heavy quick depending on configuration yes even 10 speed can be done.

The NV4500/5600 are good within their limits but suffer from overheating aftermarket has addressed some of the over heating issues but IMHO a remote fluid cooler, electric oil pump, lines and install package is required.

So, as auto trans go you have the 4L80/85e which you hate, the 4L80/85e six speed @ $7k+ or convert your box for about $4k, a Gear Vender @ $3.5 however FERM cautions against this option and the 6L90e @ $7k+ as the 6L80 does not have the tq capacity required for diesel applications. From what I've read the 4L80/85 stock trumps all the aforementioned for tq capacity.

 

[JayTheCPA]

I called and asked if the Road Ranger was do-able. When I gave the P-400's power rating and that I was going to try and make the motor deliver up to spec, I was outright told "No" and was pointed to a gear splitter.

Oh, and am not looking at the NV 6 speed as that is a heavy beast. Am looking at the ZF even though parts are getting scarce.

So even with the parts concern, a ZF6 remains the focus as I can keep it cool by going with the Ford variant. If I do decide to go with a NV4500, will get a cooler to mount on the PTO (which will also get a bit extra fluid capacity).

 

[FellowTraveler]

I called and asked if the Road Ranger was do-able. When I gave the P-400's power rating and that I was going to try and make the motor deliver up to spec, I was outright told "No" and was pointed to a gear splitter.

Oh, and am not looking at the NV 6 speed as that is a heavy beast. Am looking at the ZF even though parts are getting scarce.

So even with the parts concern, a ZF6 remains the focus as I can keep it cool by going with the Ford variant. If I do decide to go with a NV4500, will get a cooler to mount on the PTO (which will also get a bit extra fluid capacity).

That's interesting perhaps the 6.5 does not produce enough torque, I know 5.9 12 valve guys have done it.
The ZF6 sounds like a plan if you also find some spare parts or rebuild kit for it to store for any needed occasion.

 

[FellowTraveler]

4 - 6 at 70 mph.



Given only two wires are leftover, am purely speculating that they are for talking over the network with the ECM/BCM. Definitely need a better expert to confirm.

Do you know which TD07 compressor & turbine came w/ATT?

 

[JayTheCPA]

I called and asked if the Road Ranger was do-able.

Actually, need to revise that response as I confused Eaton's Road Ranger with the Advance Adapter's Ranger. The Ranger will not work with the P-400 as it's rating is 420'/lb. And was told "No" in very clear English.

In terms of Eaton's products, could not find one with a final gear that I liked. Also, all of them were too heavy.

Do you know which TD07 compressor & turbine came w/ATT?

Do not know, nor am I going to ask as the details are proprietary (and I respect that).

 

[WarWagon]

The NV-5600 is heavy, slow shifting, rare parts, hard on it's oil (shears it down), and did I mention heavy?

IMO It's night and day over the 5 speed as far as having enough gears without a huge RPM drop between them. A G56 with the newer updated OD ratio would also be a good choice and shift faster. i like the fact the NV5600 doesn't have the 5th gear nut issue of the NV 5 speed.

Seriously I can literally check my watch twice between gears on the NV5600 even while double clutching it.

 

[JayTheCPA]

A G56 with the newer updated OD ratio would also be a good choice . . .

Agree. I'd actually prefer a G56 as it is having a good production run with the Cummins. Also, a buddy has one and loves it. Only thing holding me back is a lack of bell housing (or adapter) for mating to a GM block. IIRC, there is an issue with the G56's main housing cracking, but that seems more likely to occur when owners turn up power on the Cummins well past OE specs. So cannot fault Mercedes for that one and chalk it up to self inflicted wounds of owner ego.

 

[tanman_2006]

The g56 was not built to tow in 6th and most Cummins guys tried it on the first ones because it only had a .80 OD and with 3.73's the Cummins could hack it, later they dropped to a .70 and with 3.73's most Cummins guys won't try 6th with a heavy load.

 

[JayTheCPA]

i like the fact the NV5600 doesn't have the 5th gear nut issue of the NV 5 speed.

Midwest Trans claims that they solved the 5'th gear nut issue.

The g56 was not built to tow in 6th and most Cummins guys tried it on the first ones because it only had a .80 OD and with 3.73's the Cummins could hack it, later they dropped to a .70 and with 3.73's most Cummins guys won't try 6th with a heavy load.

That is pretty much the same issue when comparing to the 4L80E. For towing, OD is too tall and direct is too low.

The cure is looking like either an auxiliary overdrive or the 8HP. Am not really fond of either and just might re-gear to 3.42's with a ZF6. If I could not row any more, would go with the 8HP presuming somebody figures out how to make it work. Another possibility for slushbox upgrade is the 8L90 as (at a minimum) it should bolt-up to the 6.5, but this presumes it is as durable as GM hopes.