Plus I never change the tune.
30HP at all times and I don't drive the truck like a sports car.
So its possible I could get a pretty long life out of the stock 68RFE.
Time will tell, only at about 40k miles now.
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Plus I never change the tune.
30HP at all times and I don't drive the truck like a sports car.
So its possible I could get a pretty long life out of the stock 68RFE.
Time will tell, only at about 40k miles now.
I’m at 40k miles as well. My plan is to upgrade the VB, here’s why.Originally Posted by Aj Grubb
The VBs are notoriously jacked from the factory. What happens because of this is excessive wear on clutch packs due to the fact the line pressure isn’t high enough to fully lock them up.
So, unless you monitor your CVIs to get an idea of if wear is occurring, you don’t really know if your trans is in good shape or wearing certain clutch packs excessively.
Also, the OD clutch pack is small and doesn’t hold power well.
Upgrading the VB will help make sure the line pressures that are being called for are effectively reaching the areas they were meant to be. Hopefully that will help with converter ballooning, OD clutch pack wearing excessively, and all other line pressure issues that plague the 68 RFE
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Its not a bad idea to upgrade the vale body. The main issue is cross leaks, that lets pressure get to the OD clutch packs when it should not which causes them to be partially applied and drag when the truck is not even in an OD gear which overheats and destroys them quick. I fail to see how upgrading the valve body will help with torque converter ballooning but whatever helps you sleep at night.
I'm just wrestling with the idea of spending money to upgrade a transmission that I plan to completely do away with in the future anyway.
Agreed. No point throwing money at a caravan trans.
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AJ,
i am am interested in where you land with your decision. I found a few post were the biggest stated difference was the valve body and converter.
As for the converter ballooning, it seems that it is the next weakest link. I also thought revmax recommends a billet converter with the billet valve body and the cheaper version for the stock converter.
I also see that suncoast has a pump half, and their statement is that the pump also needs upgraded to maintain line pressures above 165 due to an internal pressure relief. All comments above may be slightly skewed and am completely open for correction.
As for the Allison transmission, it is not much better in stock form for holding more than 100hp. I had a couple. I did a transgo on everyone and with the adaptive shift logic, you had to drive it angry all the time or it would soften the shifts and then start flaring when you did get on it. I think you would have better supported by keeping with a built 68 than getting a built Allison to work behind the Cummins. At a minimum you are going to need another tuning interface and the one I am thinking is efi live. The last time I paid attention on efi live transmission tuning only the a40 were mapped and not all parameters were complete. Just some more information to think about.
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That is one problem.
The other are each of the clutch packs that should have pressure applied to them. If a clutch pack needs 180psi to properly work and is only getting 150psi, then it won’t ever fully lock up. This destroys the clutches as the pressure isn’t high enough to lock up the clutch pack. This is the big problem with the 68RFE, the cross leak affects the actual line pressures.
The converter works similarly with multiple circuits that lock and unlock the converter. This is all controlled via the Valve Body. Ballooning of the converter happens for a few reasons but incorrect line pressure is definitely a contributing factor.
Same here. If I had the coin I’d just upgrade now. I’ll most likely upgrade the VB and then down the road the whole trans. One thing that makes me skeptical of doing anything other than a full trans build is that now by fixing the VB issue you are going to stress the other trans parts even more. So, after you fix the VB it’s possible to break other weak links.
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Yeah its a tough call. I guess one could always upgrade the valve body to prevent the cross leaks but still leave the pressure at stock. I thought about that for a while but was told that would be a waste...
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As far as an Allison being able to survive behind a Cummins, I think a lot of that has to do with the transmission tuning and how hard you plan to push it.
This video is kind of corny but if you can get passed that there is a lot of good info.
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That doesn’t really make much sense to me, more line pressure will help lock up things better. But, just upgrading the VB at stock tuning will help since more line pressure will be actually reaching its desired location.
I just ordered the Billet VB, thermostat delete, pan, and filter adapter after talking to Josh at Revmax.
Best part is the VB can be refreshed for $175 over its lifetime and can be used if you buy a full build later. Once I confirmed this it was a no brained for me. I’m planning a built tranny sometime in the next 60k+ miles or 5+ years anyway.
Any questions, call there.....he was great to talk to!
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Aj Grubb thanked for this post
Once you get the parts installed, please post up you thoughts on install and driving impression.
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