Evguy1
Senior Member
- Joined
- Feb 9, 2020
- Posts
- 360
- Reaction score
- 397
- Location
- Errington BC
- Ram Year
- 2014 RAM1500
- Engine
- Cummins ISB 170
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That will work as long as he doesn't run the truck much over a 100 mph,but his combo has the capability to exceed 150 mph,if the motor is built,and i doubt he'd have more then 1 run at top speed,before the shaft becomes a danger.Driveshaft length is a major factor to consider when it comes to critical rpm,once you approach or exceed 6ft in length,the driveshaft starts to get very big in diameter unless it's carbon fiber,and even a carbon fiber shaft will start to require a fairly big diameter.
Hmmm…given i have a brown PCM i might have to give this a try. I think tranny wiring harnesses are sold on eBay for the 8HP. Biggest issue is the wiring for the shifter.No. Depending on how in depth you go and where you buy parts from, it could very much be cheaper.
!. I know for a fact that truck sees 100+ runs on a regular basis.That will work as long as he doesn't run the truck much over a 100 mph,but his combo has the capability to exceed 150 mph,if the motor is built,and i doubt he'd have more then 1 run at top speed,before the shaft becomes a danger.Driveshaft length is a major factor to consider when it comes to critical rpm,once you approach or exceed 6ft in length,the driveshaft starts to get very big in diameter unless it's carbon fiber,and even a carbon fiber shaft will start to require a fairly big diameter.
Critical Speed
These simple driveshaft speed calculations could prevent a disaster!www.streetmusclemag.com
That's exactly what I am aiming for when I actually go to do this swap.Should be much easier and cheaper especially if the wiring is already behind the dash for the dial shifter. It took a lot of work and wiring to get to this point....but I love it. The storage "pit" that I lost was just a collector of crap so I don't miss it at all. Having manual mode on the shifter is great for towing, lets me drop a gear before a hill and hold the gear till I want to shift.
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You should inform the aftermarket drive shaft builders that are building the aftermarket shafts for the regular cab shortbox trucks, that are still blowing driveshafts and breaking transmission cases with the after market shafts then.If you were to follow the hi-po facebook pages,you'll see the after market shafts are still not the be all and end all ,of the driveshaft issues for the rcsb trucks.!. I know for a fact that truck sees 100+ runs on a regular basis.
2. I know exactly how big they get at about 6' in a quad cab because I have a custom shaft. Mine routinely sees 120 with 4.56's....know what I don't have? Neither vibration nor exploding driveshaft (since 2012).
3. If the driveshaft builder knows what they are making it for (use and parameters wise) then problems can be avoided.
And there's the main problem right there lol.If you were to follow the hi-po facebook pages
Well you're not finding to many of the fast guys on here these days,lol. A broken 8 speed is a broken 8 speed no matter where the owner is posting the pics of it .I highly doubt facebook has anything to do with breaking the case on an 8 speed though,that might be stretching things a bit far,And there's the main problem right there lol.
Thank you! Yes, it was a quite challenging Transmission Tune, but it turned out very good!So I have been trying to find a tuner to help me with my one of a kind Cummins 4 cylinder/ZF8HP70 swap. I have tried all the big name and smaller guys. They all declined due to it not being a "normal" tune. The only person who offered to help was Matt at Demon Motorsport but his experience is mostly with gas cars wanting to go fast, he did give me a few tips on tuning and it got me closer to what I needed but not all the way.
Then out of the blue I had a response on the HP Tuners forum from DodgeBoy who said he could help.
Did he ever. He worked with me over the last week to fine tune my trans so the upshifts and downshifts were right were I wanted them. It took a number of tries, I kept sending data logs after each new tune. I was impressed with his knowledge and determination to make it right. Anyone not wanting a stock canned tune should give DB a try, Dodge Boy Calibration 8HP <[email protected]>
Tell him Randy sent you. ;>)
with a stock engine, 4.56 gears and a high stall converter & the true 6spd tune id say the RFE could keep up with a stock 8HP. Modify the 8HP and obviously it’ll win.
The 8HP70 knocked just over 1/2 second on my 0-60 time. The drivability is 1000x improved over the 65RFE.As much as i love the 8HP, i would say it’s vulnerable behind high HP engines just like the old RFE is.
I see a bunch of hate posts on the RFE here, not in this thread but just in general around the site. I don’t think the hate is justified when you have people running 650-700hp crank engines with completely stock, untuned, unmodified RFEs knowing damn well the 5.7 was already within a 10hp range of the RFEs max capacity.
With a stock engine, 4.56 gears and a high stall converter & the true 6spd tune id say the RFE could keep up with a stock 8HP. Modify the 8HP and obviously it’ll win.
You'd need roughly 4.95:1 rear gears with the 6 speed RFE to have the same torque multiplication as you do with the 8speed and 3.21's in first gear,and you'd need roughly 6.00:1 rear gears to match an 8 speed with 3.92's first gear torque multiplication.As much as i love the 8HP, i would say it’s vulnerable behind high HP engines just like the old RFE is.
I see a bunch of hate posts on the RFE here, not in this thread but just in general around the site. I don’t think the hate is justified when you have people running 650-700hp crank engines with completely stock, untuned, unmodified RFEs knowing damn well the 5.7 was already within a 10hp range of the RFEs max capacity.
With a stock engine, 4.56 gears and a high stall converter & the true 6spd tune id say the RFE could keep up with a stock 8HP. Modify the 8HP and obviously it’ll win.
I moreover have an issue with how the transmission is tuned vs how bad the gearing really is.The 8HP70 knocked just over 1/2 second on my 0-60 time. The drivability is 1000x improved over the 65RFE.
With a low gear ratio of 4.56 and high stall converter - even if it keeps up with the 8HP70, it's way worse on drivability. So at best, it keeps up, while giving up a ton in day to day livabilty. That isn't a win in my book.
The 65 isn’t anywhere near dog ****. The gearing is bad but that’s about it with it. Obviously the 8 speed will always be better than it, i’m simply just stating it’s not as bad as everyone makes it out to be. With how low the rear diff is in my 300, they both have roughly the same length to 1st, but the 8HP has the advantage of a close 2nd.Nope, Not At all.
Signed, Guy with all those MODs before tuning my truck
65RFE Is absolute dog ****.
You might want to research that idea a bit more,enabling 2nd prime is still a very poor gear ratio split,2nd and 2nd prime aka 3rd gear in the 6 speed, are to close together to be a good ratio spread. Going from a 1.67:1 2nd to a 1.50:1 3rd or 2nd prime isn't really much of a gear change.This thread is several years old,but you might want to read it. The first post and post 26 might interest you.Odds are your 300 either has 2.85's or if it's a bit later version,it might even have 2.62 rear gears,comparing it to a 3.55 geared rfe truck,isn't really an apples to apples comparisionI moreover have an issue with how the transmission is tuned vs how bad the gearing really is.
If it shifted through all 6 gears, and didn’t skip 3rd, it would be a much better auto for day to day driving. It isn’t the best transmission, but it gets the job done. From what i’ve heard the biggest issue people had with them performance wise aside from the long 1st was the fact that after 2nd you had nothing at all. Enable 2P in normal shifting, and it’s MUCH better.
Yeah, unfortunately i’m aware the RFEs 2nd and “3rd” are a bit too close apart to notice in regular driving, but at WOT shifting from 1-2-3-4 gives a much improved feel over 1-2-4 in my experience.You might want to research that idea a bit more,enabling 2nd prime is still a very poor gear ratio split,2nd and 2nd prime aka 3rd gear in the 6 speed, are to close together to be a good ratio spread. Going from a 1.67:1 2nd to a 1.50:1 3rd or 2nd prime isn't really much of a gear change.This thread is several years old,but you might want to read it. The first post and post 26 might interest you.Odds are your 300 either has 2.85's or if it's a bit later version,it might even have 2.62 rear gears,comparing it to a 3.55 geared rfe truck,isn't really an apples to apples comparision
8 spd 3.21 vs 6 spd 3.92
There are some definite opinions on here about 3.92 gears. Having just purchased a 3.21 Hemi 8spd truck they would have you feel that the truck can't really do anything and is nothing more than an oversized suv. Now most of us may use our trucks for that doesn't mean they can't also be a...www.ramforum.com
Finding a used TCM or used transmission out of a 1320 Challenger is probably a hard find,but it would really wake up your 8 speed swap.I finally got my switches installed and went back and forth on several locations - on either side of gray trim on center console, or up on the dash next to the instrument cluster, or even using the OEM AUX switches(holy crap $$), but I am tired of spending money and chose cheap Amazon switches and made easily un-doable. No where near as pretty as Randy/Evguy1's shifter, but if/when something better comes along (as far as shift and mode management), I can just replace that cheap insert in the center console, and upgrade.
I've got up and down on a momentary rocker and then the un-labeled switch is a latching DPDT with Sport in the up position, Normal in the middle, and Track in the down position. Works great for shifting on the fly when I am locked out of OD, or selecting the correct gear as I don't have my tune tables nailed down just yet. The car firmware really is great, you can take advantage of so many different tables and such. I highly recommend it.
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