Go Back   Jeep Garage - Jeep Forum > Jeep Platform Discussion > Grand Cherokee SRT - WK2

Join Jeep Garage Today
Reply
 
Thread Tools Display Modes
 
  #1  
Old 09-02-2012, 10:52 AM
davidl13's Avatar
Member
My Jeep: 2012 6.4L SRT8 WK2
 
Join Date: Jun 2012
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 808
davidl13 is on a distinguished road
5spd vs 8 speed tranny

the biggest difference i can see that will help is the new tranny has a .67 reduction final gear where the 5spd has a .83 reduction...

i test drove the 2012 srt8 yesterday and i noticed that i was at 2700 rpm @ 80mph... which is very high by todays standards....

so by my calculations , the new tranny should bring the highway rpm down to 2056@80mph... this should make the car quieter and fuel consumption lower....at cruising speed... of course the paddle shifters can eliminate the weakness if need be...

this is assuming the rear gears are the same...and the efficiency of the tranny is the same... if the new tranny is far more efficient as claimed, then the rpm may be lower still....

i think this will be a very positive change....and much needed lower rpm on the flat highway....


someone let me know if my research is accurate

5sp




8 spd

__________________

__________________
Reply With Quote
  #2  
Old 09-02-2012, 12:56 PM
Scottina06's Avatar
JeepGarage Founder
My Jeep: 2014 6.4L SRT8 WK2
 
Join Date: May 2009
Location: Berea, Kentucky
Posts: 48,859
Thanks: 835
Thanked 825 Times in 636 Posts
Rep Power: 7717444
Scottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond repute
Garage
Re: 5spd vs 8 speed tranny

the ratios for the 8 speed...did you get the hp45 or hp70 ratios
__________________

__________________
SCOTT
The HARDER you work...the LUCKIER you are!
2014 REDLINE red Jeep SRT "BLOODIED Edition" 1 of 1
Previous JEEP rides-
2013 Jeep Grand Cherokee SRT-deep cherry
2013 JKU 10th anniversary-white
2006 Jeep Grand Cherokee Laredo-inferno red



Twitter-The_Jeep_Guy
Instagram-thejeep_guy

Reply With Quote
  #3  
Old 09-02-2012, 01:15 PM
davidl13's Avatar
Member
My Jeep: 2012 6.4L SRT8 WK2
 
Join Date: Jun 2012
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 808
davidl13 is on a distinguished road
Re: 5spd vs 8 speed tranny

8hp70

__________________
Reply With Quote
  #4  
Old 09-02-2012, 02:37 PM
Scottina06's Avatar
JeepGarage Founder
My Jeep: 2014 6.4L SRT8 WK2
 
Join Date: May 2009
Location: Berea, Kentucky
Posts: 48,859
Thanks: 835
Thanked 825 Times in 636 Posts
Rep Power: 7717444
Scottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond repute
Garage
Good numbers!
__________________
SCOTT
The HARDER you work...the LUCKIER you are!
2014 REDLINE red Jeep SRT "BLOODIED Edition" 1 of 1
Previous JEEP rides-
2013 Jeep Grand Cherokee SRT-deep cherry
2013 JKU 10th anniversary-white
2006 Jeep Grand Cherokee Laredo-inferno red



Twitter-The_Jeep_Guy
Instagram-thejeep_guy

Reply With Quote
  #5  
Old 09-02-2012, 02:38 PM
Scottina06's Avatar
JeepGarage Founder
My Jeep: 2014 6.4L SRT8 WK2
 
Join Date: May 2009
Location: Berea, Kentucky
Posts: 48,859
Thanks: 835
Thanked 825 Times in 636 Posts
Rep Power: 7717444
Scottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond repute
Garage
I'm gonna go drive an 8 speed LX on Tuesday to see how that tranny is......
__________________
SCOTT
The HARDER you work...the LUCKIER you are!
2014 REDLINE red Jeep SRT "BLOODIED Edition" 1 of 1
Previous JEEP rides-
2013 Jeep Grand Cherokee SRT-deep cherry
2013 JKU 10th anniversary-white
2006 Jeep Grand Cherokee Laredo-inferno red



Twitter-The_Jeep_Guy
Instagram-thejeep_guy

Reply With Quote
  #6  
Old 09-02-2012, 03:35 PM
davidl13's Avatar
Member
My Jeep: 2012 6.4L SRT8 WK2
 
Join Date: Jun 2012
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 808
davidl13 is on a distinguished road
Re: 5spd vs 8 speed tranny

i currently drive a 69 plymouth barracuda convertible with a 225 slant six (super six) and at 80mph i am doing about 3000 rpm with a 3 speed auto tranny and (either 2.92 or 2.76 rear gears, i can't remember)...and it will drive all day, but with a big v8, you just don't need the rpm's up that high for flatlands... i am sure the srt8 will drive all day as well, but with today's technology, 2700rpm @80mph for the srt8 is significantly too high for a comfortable cruising speed/rpm.... i guess they designed the gears for traffic lights, because the 5.7 doesnt behave that way.... but the 5.7 takes way too long to find its power band...

but hey my boat cruises at 4-5k rpm... so i guess its a matter of perspective... and certainly at 2700 you have instant power on tap....

i personally am torn, i really dont want to wait or pay the premium...but the OD gearing is something i will have to deal with everyday...

not sure if i can wait it out....

__________________
Reply With Quote
  #7  
Old 09-02-2012, 03:55 PM
Scottina06's Avatar
JeepGarage Founder
My Jeep: 2014 6.4L SRT8 WK2
 
Join Date: May 2009
Location: Berea, Kentucky
Posts: 48,859
Thanks: 835
Thanked 825 Times in 636 Posts
Rep Power: 7717444
Scottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond reputeScottina06 has a reputation beyond repute
Garage
Re: 5spd vs 8 speed tranny

Im the same...Im not waiting 6-9 months and then paying $70k
__________________
SCOTT
The HARDER you work...the LUCKIER you are!
2014 REDLINE red Jeep SRT "BLOODIED Edition" 1 of 1
Previous JEEP rides-
2013 Jeep Grand Cherokee SRT-deep cherry
2013 JKU 10th anniversary-white
2006 Jeep Grand Cherokee Laredo-inferno red



Twitter-The_Jeep_Guy
Instagram-thejeep_guy

Reply With Quote
  #8  
Old 09-02-2012, 08:52 PM
HAMMMERHEAD's Avatar
Member
 
Join Date: Oct 2011
Location: The Ozarks
Posts: 363
Thanks: 0
Thanked 7 Times in 7 Posts
Rep Power: 1391
HAMMMERHEAD is on a distinguished road
Re: 5spd vs 8 speed tranny

No way that much disparity. 2300-2400 RPM's at 80mph max. You would have to get in the .50 range for that kind of RPM drop.
__________________
Reply With Quote
  #9  
Old 09-03-2012, 03:57 AM
Member
 
Join Date: Apr 2012
Posts: 76
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 911
curio is on a distinguished road
Re: 5spd vs 8 speed tranny

So for the Touareg with 8spd, ts 3000rpm at 119mph...

Happy Day

Achim
__________________
Reply With Quote
  #10  
Old 09-03-2012, 09:40 AM
davidl13's Avatar
Member
My Jeep: 2012 6.4L SRT8 WK2
 
Join Date: Jun 2012
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 808
davidl13 is on a distinguished road
Re: 5spd vs 8 speed tranny

here is the math....

if you are at 2700 rpm at .83 reduction , that would mean you are at 3253 rpm at 1.00 or zero reduction (x (.83)=2700)

therefore

3253 (zero reduction) minus .67 reduction would translate to 2180....@ 80 mph...

3253 rpm (.67 reduction) = 2179 rpm


not including any extra efficiency that the new tranny may offer.... and this can be significant,... there can be as much as 10-15% slippage....but i really don't know that figure, allpar states that the new tranny is 98% efficent....which will translate into higher mpg...although i am not certain about rpm... i would think once the torque converter locks up...all is equal...


Quote:
Originally Posted by HAMMMERHEAD View Post
No way that much disparity. 2300-2400 RPM's at 80mph max. You would have to get in the .50 range for that kind of RPM drop.
__________________
Reply With Quote
  #11  
Old 09-03-2012, 11:09 AM
Mongoose9400's Avatar
Member
My Jeep: 2012 6.4L WK2
 
Join Date: Feb 2012
Location: Rio Rancho, NM
Posts: 829
Thanks: 0
Thanked 51 Times in 42 Posts
Rep Power: 0
Mongoose9400 is an unknown quantity at this point
There is nothing wrong cruising at 80ish mph in the 2700-3000 rpm range. Just pay a little more for fuel. The WK1 SRT8 rev higher than the WK2 SRT8 at the same speeds. Many WK1 SRT8 with high mileage, the rpms won't harm the Jeep. Hell, I've put 14k highway miles on my WK2 SRT8 and my highway speeds are 80+ mph. Even drove it 30 hours straight one trip. The Jeep can take it no problems.


Sent from my iPhone 4S
__________________
Reply With Quote
  #12  
Old 09-03-2012, 12:02 PM
davidl13's Avatar
Member
My Jeep: 2012 6.4L SRT8 WK2
 
Join Date: Jun 2012
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 808
davidl13 is on a distinguished road
Re: 5spd vs 8 speed tranny

true that, it is just more comfortable at a lower crusing rpm for longer trips.. (mpg, noise, vibration etc...) ... my 69 barracuda can do it all day long at 3000 rpm and that is a pretty old engine....all original, no rebuilds...
__________________

__________________
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
8 speed tranny RECDOG Grand Cherokee - WK2 - 1 08-13-2012 04:00 PM
think my tranny is going... tig488 Troubleshooting/Problems 19 07-02-2012 10:27 AM
8 speed tranny? Dream on... mr.jason Grand Cherokee SRT - WK2 38 02-27-2012 07:02 AM
'00 42RE Tranny vs. '96 43RE Tranny freemyer Troubleshooting/Problems 6 07-07-2011 11:03 PM
8 speed tranny update :) B.P.O.D Grand Cherokee - WK2 - 8 12-31-2010 05:22 PM

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 02:07 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community