For those thinking of a rebuild or upgrading their ZF for towing might find this interesting !!!

The Ford R6-80 Automatic is a upgraded US licenced built ZF 6HP26 gearbox. Ford loved the auto, but needed it stronger for it's big motors.

I found the following threads on the Aussie V8 forum, I'll keep watching and post anything new !!!


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For a while I have been asked a lot of questions about the 6HP26 input shaft by the Ford guys.


Customers have advised me that this reasonably simple upgrade by some companies can cost between 5 and 7k and that's without having the converter looked at or upgraded.

I think its common knowledge now that the ZF box will snap an input shaft and the intermediate shaft if you're pushing it, the transmission software/tune is a contributing factor but upgrading the two shafts will increase the reliability of the transmission significantly. I have seen and heard of cars running into the 8's at over 160 mph in America with the 6R80. The ZF is pretty much an identical transmission with many components directly interchangeable, some need a little modification.

Some shops have a replacement shaft for both pieces and others use Ford 6R80 components.

Personally I like the 6R80 parts; they are cheaper, proven to be up to the task and come with several added benefits.

The 6R80 pump assembly will go straight into a 6HP26; it has a larger diameter stator shaft with the same spline as many GM transmissions, Powerglide and Turbo 400 etc. The pump gears are wider which is desirable, especially as the ZF unit is so hard on bushes. The GM spline opens the door to a wider range of high performance converter parts, multi plate clutches and performance converter combinations.

For those that want to stick with the 6HP26 Converter, the 6R80 splines can be easily cut into the ZF turbine hub and a GM sprag inner race is available.

The 6R80 input shaft is also known as the ?E? clutch drum; this part is significantly larger in diameter than the 6HP26 shaft. The sealing ring grooves are also not as deep as the ZF shaft so it is superior in all ways. When using the 6R80 shaft you cannot use the ZF sealing rings. You must use the 6R80 sealing rings which are available as both scarf cut Teflon or a solid Teflon ring whatever you prefer.

The ?E? Clutch commonly has 6 lined plates and some factory boxes will have 7 depending on designation. The 6 plate clutch has 3.0 mm steel plates while the 7 plate has 2.4 mm steels.

I have toyed with the idea of having steel plates custom made to accommodate more frictions but I think 7 plates does the job well and the factory steel plates are treated to increase heat resistance and lubricity adding to its durability. Any plates I can have made won't have these advantages.
Exedy have a kit available with some friction plates and steel plates which I have used but it is also quite expensive. I don't see any significant advantage to use the Exedy plates over genuine ZF frictions and steels but others may have their own opinion on that. I have used the ZF steel plates with the Exedy frictions without any problems.

This transmission has a desirable range of piston travel in the ?E? clutch, adding more lined plates requires more clearance and therefore increased piston travel. Adding more frictions can come with drawbacks with shift quality and the transmission programming. The factory uses a maximum of 7 plates and that's enough to snap shafts so I don't think friction capacity is a big problem for the majority of people.

The ZF has a couple of different types of intermediate shafts and both will snap at high horsepower levels. Some people believe cryogenic treatment is enough to eliminate the weakness but I am not convinced. Billet shafts made locally are available for roughly $1400AU to $1600AU.

There is a 6R80 300M shaft available from Canada which retails there for about $565US.

The upgrade components are readily available and are not that expensive compared to the prices that have been reported. The components can be supplied as a kit along with a strengthened converter for around 2k.

With the transmission on the bench it takes about 3-4 hours to carry out the work. Guys who have done it a few times will be able to do it in less than 2 hours.

It is worth doing a little research on this upgrade as there is serious money to be saved if you're contemplating or need to have it done.
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2. 26-04-2015, 09:34 AM
Sonnax website they list this torque converter sizes:

- 6hp26 - 255mm, 260mm, 275mm and 280mm.

- 6r80 - 260mm (later), 280mm (earlier) and 280mm (later)

With one is the correct for a FI high torque rwd car?

I look to Sonnax available upgrade parts for both gearboxes: 6hp26 and 6r80.

But when looking for AM 6r80 torque converters i found:

1. Circle D Stage3, multidisk, 245mm, 258mm, 265mm, stall range from 3000-4200rpm. Price $1.200

2. Revomax Stage5, 203mm (8"), 228mm (9"), 241mm (9.5"), 254mm (10"), stall range from 2500-7000rpm. Price $800

Is all the sizes good to fit? Does the torque converter case always the same size despite the interior disk diameter?

I want the lowest rpm stall because my car is a twinturbo diesel engine and therefore the max boost came around 2000rpm. It has now 440hp and 850nm with already some gearbox issues (ZF rated for 600nm) and my goal is 500hp and +900nm.

Sorry if my questions may be silly but i am not in my confort zone with the auto gearboxes. I know a guy willing to do the job with sonnax parts and exedy clutch kit but his price is too high and the claim of reliable 900nm sounds unreal without torque converter and input/intermediate shaft upgrade.

I haven't got around to finishing this thread off.
Some people having trouble finding some parts due to Ford and Mazda's poor diagrams.
3 bearings that are required are:
1 x 9L3P7H 375AA
1 x 6L2P7D 283AA
1 x 6L2P7A 453AC
These bearings can be sourced from Ford or Mazda.

When I get a chance I will look at altering the rear of the trans to accept more 6R80 parts as the power potential for the 6R80 is much higher than the ZF unit.
Would also keep costs down compared to buying the after market intermediate shaft for the 6HP26. For that money you could buy a complete 6R80 and the TCS intermediate shaft and be able to go well into the 8 second zone.
There will be more after market parts available for the 6R80 in the coming years, it'll be here for a while yet."

The video of the R6-80 Drag Car auto strip down and rebuild with the improved components is well worth a look. This auto only required a few mods for this Drag Car Class.

Laurie


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