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  #13  
Old 05-19-2014, 09:47 AM
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re: For those of you with an 8 speed on the V6

Just my 2 cents I have posted elsewhere. The V6 only tranny (845RE) is made by Chrysler under license from ZF and the V8/Diesel tranny (8HP70) is made by ZF and shipped to Chrysler.

The main difference being that Chrysler is taking (documented) the base ZF 845RE design and modifying it with stronger clutches, etc.. to handle the higher torque loads it is throwing it. This tranny has had "some" mechanical issues with valve bodies, etc... The 8HP70 is sourced and untouched mechanically and has had no mechanical issues. IMHO, the design mods are the source of any mechanical issues with V6 tranny.

Both tranny's have had some shifting/behavior issues with the V8/Diesel being very little reported and mostly solved with a TSB. The V6 tranny, however, had major shifting problems that are somewhat? addressed with TSB's thus far. All the shifting issues I am hearing about with the V6 tranny, slamming downshifts/hesitation from start...., sure sound like they are clutch (mechanical gear engagement) related to me. And since that was the major design modification by Chrysler they seem focused on trying to tame the issues with programming changes but seem to still be working on it.

I guess my point is that it makes sense what you guys are seeing in V6 tranny performance given the design alteration, IMHO.
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  #14  
Old 05-19-2014, 10:02 AM
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re: For those of you with an 8 speed on the V6

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Originally Posted by redddog View Post
I have a really stupid question about modes. You'll have to bear with me as this is the first vehicle I've ever had that hasn't had full time AWD.

Can you shift between "sport" and regular "drive" modes while moving? And is that true with the select trerrain as well?
Thanks and sorry to dumb this thread down so much.

You can shift from drive to sport while moving. No problem at all. Also true with selec terrain. You can't go to certain ride heights if you're going over a certain speed though. Assuming you have an air suspension equipped jeep there...




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  #15  
Old 05-19-2014, 10:11 AM
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re: For those of you with an 8 speed on the V6

Quote:
Originally Posted by 14SummitHemi View Post
Just my 2 cents I have posted elsewhere. The V6 only tranny (845RE) is made by Chrysler under license from ZF and the V8/Diesel tranny (8HP70) is made by ZF and shipped to Chrysler.

The main difference being that Chrysler is taking (documented) the base ZF 845RE design and modifying it with stronger clutches, etc.. to handle the higher torque loads it is throwing it. This tranny has had "some" mechanical issues with valve bodies, etc... The 8HP70 is sourced and untouched mechanically and has had no mechanical issues. IMHO, the design mods are the source of any mechanical issues with V6 tranny.

Both tranny's have had some shifting/behavior issues with the V8/Diesel being very little reported and mostly solved with a TSB. The V6 tranny, however, had major shifting problems that are somewhat? addressed with TSB's thus far. All the shifting issues I am hearing about with the V6 tranny, slamming downshifts/hesitation from start...., sure sound like they are clutch (mechanical gear engagement) related to me. And since that was the major design modification by Chrysler they seem focused on trying to tame the issues with programming changes but seem to still be working on it.

I guess my point is that it makes sense what you guys are seeing in V6 tranny performance given the design alteration, IMHO.
Makes you wonder why they don't just switch to the 8HP70 for all models (I think even the SRT uses it). Problem solved...
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  #16  
Old 05-19-2014, 10:15 AM
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re: For those of you with an 8 speed on the V6

Ya, hear ya....but size, weight, etc...

I was not unhappy when in my research I saw that the Hemi used the same tranny as the SRT.
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Old 05-19-2014, 10:29 AM
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re: For those of you with an 8 speed on the V6

Quote:
Originally Posted by 14SummitHemi View Post
Ya, hear ya....but size, weight, etc...

I was not unhappy when in my research I saw that the Hemi used the same tranny as the SRT.
Well, there is a difference, but not a huge one. I could only find size/weight for the 2wd versions, but here they are:

Length x Diameter, Weight
845: 672mm x 178mm, 176 lbs
870: 682mm x 200mm, 203 lbs

With all the issues, I'd just add the 27lbs. I'm sure the difference in length and diameter would be easily dealt with as well.
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  #18  
Old 05-19-2014, 10:33 AM
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re: For those of you with an 8 speed on the V6

Agreed. There is plenty of room in the engine bay with a V6 in there.
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Old 05-19-2014, 10:45 AM
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Re: For those of you with an 8 speed on the V6

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Originally Posted by Roger Ramjet View Post
Makes you wonder why they don't just switch to the 8HP70 for all models (I think even the SRT uses it). Problem solved...
Cost, The upgrade to the V8 or the Diesel includes the more expensive transmission. Even though the 2 transmissions are similar they share almost no parts (even when made by ZF). 45 (845RE) Stands for 450 NM of torque and 70 (70HP) Stands for 700NM of torque.

Thread title updated.
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Old 05-19-2014, 10:47 AM
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Guaranteed a cost decision. "Over" design leads to unneccesary extra cost, etc....

Plus gonna bet it's a platform and future of the line decision , i.e. smaller engines smaller trannys smaller vehicles....It's a small small world.

Don't shoot the messenger -
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Old 05-19-2014, 11:22 AM
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Re: For those of you with an 8 speed on the V6

Quote:
Originally Posted by Willx View Post
Cost, The upgrade to the V8 or the Diesel includes the more expensive transmission. Even though the 2 transmissions are similar they share almost no parts (even when made by ZF). 45 (845RE) Stands for 450 NM of torque and 70 (70HP) Stands for 700NM of torque.

Thread title updated.
My answer to that is... having been in the (German) auto parts business for 8 years, I would bet Chrysler would actually save money over what it cost to source and stock parts for an additional transmission model. I'll bet the main reason for the smaller tranny was weight savings in order to help MPG.
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Old 05-19-2014, 11:33 AM
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Re: For those of you with an 8 speed on the V6

Quote:
Originally Posted by Willx View Post
Cost, The upgrade to the V8 or the Diesel includes the more expensive transmission. Even though the 2 transmissions are similar they share almost no parts (even when made by ZF). 45 (845RE) Stands for 450 NM of torque and 70 (70HP) Stands for 700NM of torque.

Thread title updated.
Thanks for updated the thread title. I got some assistance last night, but only updated it on my response.. Weird.

Also, just curious as to why the internals are so different? Sure, different hp and torque ratings (I get that), but in terms of sourcing material, that just increases the cost of the car, but where is the benefit?
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  #23  
Old 05-19-2014, 11:40 AM
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Quote:
Originally Posted by Roger Ramjet View Post

My answer to that is... having been in the (German) auto parts business for 8 years, I would bet Chrysler would actually save money over what it cost to source and stock parts for an additional transmission model. I'll bet the main reason for the smaller tranny was weight savings in order to help MPG.
Chrysler builds the 845RE and buys the 70HP at this point so maybe when they build the heavier 8 speed themselves that might be true but not right now.
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Old 05-19-2014, 11:42 AM
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I will post some more detailed info about the two transmissions later. Not easy to reference the right material from my phone
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