68RFE trans differences?

[dcs1968]

I was wondering if there was a difference between the 68RFE transmissions used in the 650 ft lbs rated engines and the 800 ft lbs ones. If the later is beefed up for the added power is it compatible with the lower output trucks?

Thanks

 

[wyosteve]

I believe the 68RFE only comes in the 800 torque model. The 650 torque model uses the manual G56 transmission.

 

[transe]

In general, yes, a newer 68RFE trans will work fine in an older truck, EXCEPT for one critical item: the valve body assy. The OD solenoid was removed for 2011 MY, so if you put a 2011+ trans into an older truck, you will blow an immediate P0760 (OD solenoid circuit) fault, and the trans will be in perpetual limp-in. The main change was the solenoid module, but the steel valve body separator plate also changed, and two of the check balls were deleted. So the easiest thing to do (if transplanting a 2011+ trans into a 2010 or older truck) is to simply swap the old valve body into the new trans. However, the 2011 valve body is anodized, and a 2007-2009 valve body will likely be worn, so a better option is to swap the old solenoid module (the chunk of parts that has the main electrical connector on it), and the old thin steel separator plate, into the new trans, along with the two "extra" check balls (so the VB assy in the new trans will have 7 check balls total). Unscrew all the VB screws that are on the BOTTOM of the assembly, to split it apart. Do NOT remove the screws that are on TOP of the solenoid module.

Oh, and the torque converter performance curve has changed a couple times over the years, but you should be able to use a newer converter in an older truck with no issues. Also, starting in mid-2010 MY we went to a 4x4-style oil pan and filter on all 68RFEs (before that, 4x2 models used a different oil pan and filter). So if you do swap a newer 4x2 trans into an older truck, be aware that you may need to start using the "wrong" (4x4 style) sump filter with it.

 

[dcs1968]

Thanks for the info TransEngineer! So are the hard parts such as the input shaft, clutch packs, and such the same? I am just wondering how much leeway I have with this trans. My truck is a 350/650 and was wondering if I could add some power and still be ok. If this trans is basically the same as the ones in the 800 ft lbs trucks . I have seen posts where it is being said these trans are weak in stock form and will be toast quick with any power added. What are the most critical parts to upgrade? Thanks again!

 

[transe]

Thanks for the info TransEngineer! So are the hard parts such as the input shaft, clutch packs, and such the same? I am just wondering how much leeway I have with this trans. My truck is a 350/650 and was wondering if I could add some power and still be ok. If this trans is basically the same as the ones in the 800 ft lbs trucks . I have seen posts where it is being said these trans are weak in stock form and will be toast quick with any power added. What are the most critical parts to upgrade? Thanks again!

Internal hard parts are basically the same. There have been a few minor changes made over the years, but nothing that significantly affects torque capacity. The one thing that did change (for the 800 ft-lb engine) was the converter. It was upgraded for 2012 MY, so using a 2012+ (or aftermarket) converter would be a good idea.

Internally, it seems like the OD clutch pack is the typical weak link. I am not intimately familiar with what aftermarket parts are available (to upgrade the OD clutch), although I know some vendors do offer various upgrades. If you want to avoid pulling the trans and tearing into it (to upgrade the OD clutch pack), I would recommend running a trans "tuner" that provides increased line pressure, along with a modified valve body assy (that allows higher line pressure levels in Drive). These are available in the aftermarket. There are also line pressure "foolers" that plug into the line pressure sensor harness, and promise to raise your line pressure, but I don't think they give as much benefit as might be expected, and they cannot boost line pressure as much as a modified valve body assy.

 

[dcs1968]

Again thank you TransEngineer. It gives me a few things to think about. I am not looking to add too much power but it would be nice to have 800 Ft lbs. My goal is to run clean and be reliable while making decent power.

 

[MA2LA]

I did a revmax valve body and their line pressure box and it did work ends for the trans but a couple weeks ago something went nuts a a pressure spike blow the valve body part and toasted the trans. I kinda expected the trans to let go at some point since it has 200k on it but it had been operating perfect and this truck is used very hard towing 12k plus in stop and go traffic and even when not towing it weighs over 10k. We had a smarty Jr on it since it went out of warenty and mainly kept it on the economy setting since the towing was a little much on the stock trans. With the valve Body and box the trans seemed fin with the 75 hp towing setting even with heavy loads.

 

[transe]

I did a revmax valve body and their line pressure box and it did work ends for the trans but a couple weeks ago something went nuts a a pressure spike blow the valve body part and toasted the trans. I kinda expected the trans to let go at some point since it has 200k on it but it had been operating perfect and this truck is used very hard towing 12k plus in stop and go traffic and even when not towing it weighs over 10k. We had a smarty Jr on it since it went out of warenty and mainly kept it on the economy setting since the towing was a little much on the stock trans. With the valve Body and box the trans seemed fin with the 75 hp towing setting even with heavy loads.

If you blew the accumulator cover off (actually, one end of that cover), there is a repair kit available from Mopar, and odds are the trans is NOT toast. The kit is 05174633AB and costs about $20. You just drop the pan and VB to fix it.

 

[Torqmatix]

Internal hard parts are basically the same. There have been a few minor changes made over the years, but nothing that significantly affects torque capacity. The one thing that did change (for the 800 ft-lb engine) was the converter. It was upgraded for 2012 MY, so using a 2012+ (or aftermarket) converter would be a good idea.

Internally, it seems like the OD clutch pack is the typical weak link. I am not intimately familiar with what aftermarket parts are available (to upgrade the OD clutch), although I know some vendors do offer various upgrades. If you want to avoid pulling the trans and tearing into it (to upgrade the OD clutch pack), I would recommend running a trans "tuner" that provides increased line pressure, along with a modified valve body assy (that allows higher line pressure levels in Drive). These are available in the aftermarket. There are also line pressure "foolers" that plug into the line pressure sensor harness, and promise to raise your line pressure, but I don't think they give as much benefit as might be expected, and they cannot boost line pressure as much as a modified valve body assy.

The "foolers" you mention are just an inline diode that supposedly add around 10-15 psi, yet I have yet to test one personally. I've heard 50/50 feedback from some who claim it works great to complaints that it "works goofy".
The only "valve" body mods, considering there is only one valve, that can be done are accumulator springs/spacers, a heavy duty accumulator plate, and an oversized valve. I agree the 2011 up valve body would be a better choice because of being anodized, however, I've yet to swap 5 checkball vb with a 7 checkball vb as I've only been advised this does not interchange properly.
The o/d solenoid was omitted from the solenoid pack in 2009 and can be identified by a grey connector.

Really, any performance increase will need to be done via custom tuning with software such as HP Tuners, Diablosport, etc. The computer receives data from the trans and adjusts to keep it within programmed specs (this could be why the inline diodes end up not working after the trans adapts?) Billet shafts are available but really unnecessary unless you are running a triple disc converter and over 600hp or so. High energy aftermarket clutches are about the only real internal upgrade you can do for longevity against slipping. Usually adding more frictions means you are subtracting steel mass which absorbs that heat energy. I would restore all of my hydraulic functions with oversized valves in the pump, solenoid switch valve, NEW solenoid block, high energy frictions, NEW bonded pistons, Single disc billet converter & custom programming by someone who knows what they are doing.

 

[dcs1968]

I would like to thank everyone for their responses. This group is a very valuable resource.