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Just wondering if anyone knows how much horsepower would be safe to add to the hemi with the stock 65rfe tranny.
 

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What you might be disappointed to find, if you put her on a dyno, you'll see how much power the stock program sucks out of the motor. I watched a new 13 395hp Ram on a Mustang dyno put down 290 rwhp Saturday, bone stock. 105 hp missing, hmm. My 05 with the 345 hp hemi with a few mods puts down almost 320 rwhp on the same dyno. The answer, first get a Diablo tuner, then get with "hemifever" to unlock all the hidden hp. I've sprayed many 100 shots of nitrous (around 400 rwhp) and at 210,000 miles, no trans problems. I run a Sonnax line booster, though. I believe if you approach 500 rwhp, better think of upgrades. Check with Sharadon, maybe ATS. I believe some of the stronger parts from the 68RE Cummins trans will fit, too. First
 

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Just wondering if anyone knows how much horsepower would be safe to add to the hemi with the stock 65rfe tranny.

I think you'll find for drag racing, or other street type short duration bursts, you need to worry about the torque limitations of this tranny, not the HP.
Long duration HP limitations ( road races) would be geared ( pun intended) toward the tranny cooling system.
 

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65RFE is rated for 500 lb tq. its a pretty decent transmission. Other than the weird tall gear ratios which suck for towing. Just keep an eye on your trans temps. Anything above 180 is a no no with stock fluid. Unless you run a fluid like Amsoil that doesnt break down.

Dont be doing any pulls past 4th gear. Thats a good way to destroy any transmission. Pulling in over drive that is.

65 RFE = 500tq
545RFE - 450tq

Some say the extra strength comes from the converter since these transmissions are pretty much the same internally other than the extra gear of course.
 

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There is no extra gear

545RFE:

1st 3.00:1
2nd 1.67:1
2nd Prime 1.50:1*
3rd 1.00:1
4th 0.75:1
5th 0.67:1

65RFE:

1st 3.00:1
2nd 1.67:1
3rd 1.50:1*
4th 1.00:1
5th 0.75:1
6th 0.67:1

Exact Same turd with a programming tweak
...and a slightly different valve body.

*2nd prime (3rd in the 65RFE) is the kick-down aka "passing gear"
and is not part of the normal upshift sequence.
The only way to include it in the up-shift is via manual or tow/haul mode.

There are plenty of failures of both with just minor bolt on's
any kind of forced induction is a death sentence to the OD clutch pack


Both transmissions are based on the 45FRE, originally designed to go behind a 235hp 4.7L V8
in the 1999 Jeep Grand Cherokee, Dodge re-programmed a second OD gear and called it a 545RFE
they put it behind the 345HP 2G Hemi Ram in 2002.

I don't know why they thought it would still be good enough
for the 4G Rams new Eagle Hemi in 2009 rated at 390hp. FAIL!


The next six speed derived from the 545RFE was the 65RFE, used with V8 versions of the Ram 1500, Durango, and Grand Cherokee. The 65RFE only has six forward gears in ERS/AutoStick mode or kickdown mode; it is essentially a software and name change, which allows people to reach the “prime” gear via ERS as well as than kickdown. An internal Chrysler communiqué to dealers summarized the change in a similar fashion.
Source: http://www.allpar.com/mopar/transmissions/545RFE.html
 

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While the numbers might be correct when mopar numbered there RFE transmissions. How do you explain the build sheets that list the 6-speed as a 645rfe? That transmission, by your numbers would have the same 450tq rating as the 545rfe... There was no 65rfe, it's the 645rfe transmission for 2012.
 

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I believe the 6 speed is at it's mechanical limit with the stock 5.7 engine...this fact killed the daydream of installing an Edelbrock Supercharger...that's even before my wife slapped me back into reality. She would NEVER let that kind of money be spent on my toy.
 

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While the numbers might be correct when mopar numbered there RFE transmissions. How do you explain the build sheets that list the 6-speed as a 645rfe? That transmission, by your numbers would have the same 450tq rating as the 545rfe... There was no 65rfe, it's the 645rfe transmission for 2012.
Engine output figures are given as net HP and torque, that is with all accessories mounted and numbers taken at the crank. This is the way every manufacturer does it and no vehicle is making those numbers at the wheels because there are parasitic losses incurred when that power is transmitted through the drivetrain.

There is no such thing as a 645RFE, there was the 45RFE that came out in 1998 behind the 4.7L PowerTech V8. In 2001 it became the 545 RFE with the addition of a taller overdrive ratio and a programming change and lasted until 2012 when another programming change resulted in the name change to 65RFE.

Transmission input capacity is measured in torque (Newton-meters for Europeans or lb-ft for Americans) not horsepower. For the 45/545/65RFE the max capacity is 410 lb-ft; for the 8HP70 that has all but replaced it the capacity is 516 lb-ft.
 

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I just found out the hard way the torque rating of the 65rfe. Nuked the torque converter, 2nd and 4th gear clutches. Had it rebuilt right though. New updated TC, transgo shift kit, line booster, and new clutches. Have LSD 3.55 rear end. My mods that the tranny couldn't handle include, bbk shorty headers, k&n full CAI system, edge tune, pedal commander, and magnaflow cat back. Stock trans couldn't take it and committed suicide after 30000 miles. Upgraded rebuilt trans should handle it better and would recommend doing trans first, power adders later. Cost me $4700 CDN after tax. Food for thought for anyone chasing more power.
 

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I just found out the hard way the torque rating of the 65rfe. Nuked the torque converter, 2nd and 4th gear clutches. Had it rebuilt right though. New updated TC, transgo shift kit, line booster, and new clutches. Have LSD 3.55 rear end. My mods that the tranny couldn't handle include, bbk shorty headers, k&n full CAI system, edge tune, pedal commander, and magnaflow cat back. Stock trans couldn't take it and committed suicide after 30000 miles. Upgraded rebuilt trans should handle it better and would recommend doing trans first, power adders later. Cost me $4700 CDN after tax. Food for thought for anyone chasing more power.
Probably the tune. You were already only 3 lb-ft short of the max capacity and any adjustments to shift points can reduce its ability to handle the output
 

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I just found out the hard way the torque rating of the 65rfe. Nuked the torque converter, 2nd and 4th gear clutches. Had it rebuilt right though. New updated TC, transgo shift kit, line booster, and new clutches. Have LSD 3.55 rear end. My mods that the tranny couldn't handle include, bbk shorty headers, k&n full CAI system, edge tune, pedal commander, and magnaflow cat back. Stock trans couldn't take it and committed suicide after 30000 miles. Upgraded rebuilt trans should handle it better and would recommend doing trans first, power adders later. Cost me $4700 CDN after tax. Food for thought for anyone chasing more power.
Probably the tune. You were already only 3 lb-ft short of the max capacity and and adjustments to shift points can reduce its ability to handle the output
Agreed.
 
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