Has anyone done this swap? The C6 in my 86 Grand Villa is tired, and I was thinking maybe it might be a better idea to put a sturdier transmission. The Allison is also a 4 speed, which couldn't hurt.
I've got the OREG with the V-814 chassis and a Ford 7.3 IDI engine. I sort of doubt anyone else has such a chimera of a vehicle. I think the only thing left from the original drivetrain on this beast is the C6. I'm guessing since the 545 was used by international on the 7.3IDI, it would just bolt up?
Or maybe there is a better option? This is the first vehicle I've ever owned with an auto, so I have a lot to learn about them.
MT643 is almost identical to the AT-545 but locks up in fourth gear. I believe it is about 1/2"-1" longer.
Might want to check with James Holder the Service Manager at Tennessee RV.
I believe the 643 locks the torque converter in both 3rd and 4th.
Yes, a lot more robust than the 545.
But, I believe their "bolt up pattern" to the engine is different. Do not know which has same pattern as C6.
Here are the two specification sheets for the two trannys.
Brett is correct. The AT545 mounts to a SAE #2 bell housing and the MT643 mounts to a SAE #3 bell housing.
Seems more comparisons are required.+
I got my info/recommendation from James Holder so hopefully someone else can do some more research on this swap.
I was worried that the 643 needed a computer, but then I know very little about them. No Computers on the old 7.3s.
Another dumb question- Is there any difference between transmissions for diesel pushers and front engine vehicles?
It is a hydraulic transmission, not electronic.
I guess the 643 would be the best choice, if it fits. I was told the 7.3idi fits a sae #2 housing.
Yup, if it bolts up, the 643 is a much better choice. Rated for higher HP and Torque and very importantly, torque converter locks up in 3rd and 4th gear.
So, better MPG and less transmission fluid heating.
Here's a consideration. The C6 in there now is 175 pounds. The AT542 is 253 pounds. the MT643 is a great big juicy 510 pounds; 638 with the retarder. This probably isn't a big deal with the 917 chassis, but i have the 814 which already is 200 pounds heavier with the diesel swap.
The C 6 is a pretty good trans as is . Does it have a bigfat cooler and shift kit ? it should do what you ask of it.
When you say the c-6 is tired, is it slipping or does it just have "morning sickness" when cold doesn't up shift?
What transmission does Ford use in back of the Powerstroke or Binder diesel.? Seems to me that would be the quick fix, maybe with a shorter tail shaft.
The C-6 is a stout trans. enough to hold on to a Ford big block so rebuild and shift kit ? ^.^d
My C6 slips badly. its fine in reverse, but from a stop its really bad. I wasn't slipping so badly i couldn't drive it, so I thought maybe it was just the burnt looking fluid, but when I changed that it barely moves at all in forward, so I assume the PO dumped a bunch of that stop slip into it. My assumption with that is that it needs a rebuild, but this is the first vehicle I've owned with an auto, so I am far from an expert.
Then adding to the fact that the C6 is only a 3 speed, it just seems if i do have to swap it out, I should consider something more robust and with at least 4 speeds.
Whenever you put new fluid in an auto trans that has slipping problems, the detergent in the new fluid cleans the remaining clutch material off and they slip worse. I don't believe you were tricked by the seller with a cocktail. If the fluid was brown and smelly it was bad. I agree if you have to rebuild something use the heavier duty one.
Ah. I had no idea of that. I had read if a transmission is slipping and the fluid was burnt, changing it out might fix the problem.
I also wouldn't say i was tricked. Its a long story, but I give the PO a pass on a lot of the questionable stuff he did to this coach.
I think they moved to the E40D with the Powerstroke. I have heard with the C6, you can beef up some of the parts on rebuild and make it a lot sturdier, so that is an option too.
I does have a transmission cooler in front of the radiator, and I wouldn't know a shift kit if it came up and bit me.
The e4od would be a benefit. They are strong and common. That being said nothing wrong with a good c6
What is the final drive ratio? What is the cruise RPM? If the Cruise RPM is just under max torque, you may not see any fuel reduction with more overdrive.
In your case with a conversion from gas to diesel, the RPMs may indeed like to be reduced a little . 22-2400 Is a nice RPM for those Fords. If it is under 2500, I would rebuild the C6, if over I would look for the big OD Ford trans. Both will be a lot less hassle - money than the heavy Allisons. The 643 is direct in high gear, not sure on the smaller one. Plus the rotating stuff weighs a lot more and will result is less performance .
I wish i could answer these questions. I've only had it a few months and I just got it running, and only drove it enough to tell the transmission was bad. Its got a 2 speed Spicer rear end which i also just got working, and have no Idea what the ratios are for either.
The E4OD like It's Toby mentioned is the big OD? the only real issue I see there is that its electronic, so would I would have to get a transmission controller?
The diff may have a tag on it .or you can jack it up and count the turns. Look at U tube, you only need to spin one side . My guess is 4.10 But I have no idea what diff your coach came with .
Most 2 speed rears are underdrives as installed . If you have true overdrive and come up with a total gear ratio under 4/1 (3.9, 3.7 etc) than the direct top gear trans should be fine.
Figure out how/if the OD /2 speed works .
Figure the diff gear
ask around for optimal cruise RPM for your engine.
Post what you find and I'l be happy to do some math research.
Gear Up! (http://www.scirocco.org/gears/) this shows how to figure gearsets and tire rollout vs speed.
The easiest way to determine your gear needs is to coax it down the road one more time with a GPS and tack working.
IMHO ;Short story and most cost effective is to get the C6 rebuilt with a HD shift kit and clutch packs and deal with the resulting cruise speed .
****Editttt. If the 2 speed is a gear vender aftermarket OD than you should be good on the overall gear ratio.
MY racing partner tows with a 7.3and says that 2300 RPM works the best. He has towed @ 2800 with his C6 @ 70MPH .
For the AEOD Ford trans , you need a controller and some are using a Microsquirt ECU. The same thing that I sell and install . The parts are about 400$ ECU and Harness.
He has the Gear vender for sale at 1000$ with controller . Corrected, 1500$ sorry.
The OD Ford can be built for about 1500 $ here inFL/Tampa area.
Rebuild the c6 IMO
What Mike is saying makes the most sense to me ........HD rebuild on the C-6 and count the turns on the rear axle.
We had a feed truck on the ranch ( 1981 ) that had the Spicer split shift and it worked as an under drive, but it had a Clark 5 speed stick so split shifts were easy to accomplish, not sure how it works with an automatic, would need the shift kit just to control trans gear selection.
Mick
Yeah, keeping the C6 and beefing it up a bit is probably the best answer. not the most fun one though.
Bottom line is the C6 is a 175 lb transmission with no lockup. You can't expect it to have the life of the heavier transmission and without lockup, it's going to get worse fuel mileage plus it's going to produce a lot more heat with the weight of the GV.
Would be a lot better with a HD automatic or 5 speed manual. The manual worked really well behind the 7.3 in our old devil. The 5 speed has an OD fifth too.
Pierce
[quote author=Pierce & Gaylie Stewart link=msg=276476 date=1497645226
Would be a lot better with a HD automatic or 5 speed manual. The manual worked really well behind the 7.3 in our old devil. The 5 speed has an OD fifth too.
Pierce
[/quote]
I would love to throw a 5 speed in here. Part of the problem for me with my current transmission is that i just don't have any experience in automatics. Retrofitting a 30 foot run of shifter and clutch cables sounds a little daunting though.
Sorry, I was thinking of a front engined Foretravel. Clutch is hydraulic so that would not be a problem. Shift linkage would take a bit of engineering.
If your C6 is a three speed, that's a big gap between gears. Third can't be too tall and first can't be too low. Just guessing but 55-60 would be about it with fairly high RPM on the freeway. Our 7.3 was happy with a lot of torque low down and a good midrange but lost the really smooth feeling at high RPM. It was happy at about 60 in OD fifth.
Must be a forum with experience with a possible auto trans swap. You might try B&M Transmissions. They have been in the business since I was a little kid. 1.707.544.4761
Pierce
One thing the PO did to help out the C6 was add a 2 speed spicer rear end. Before I fixed that, it was stuck in low and 55 was abotu are fast as it wanted to go. The transmission has been acting up since, so i haven't had a chance to put it through it's paces. No Idea what the gear ratio is... there are no tags on the case at all.
I don't think it would be practical to be splitting the gears with the rear end, instead using it as an overdrive. Only having to back out of the throttle one time. All C- 6's were direct in third gear. The 6's are much more common for repairs also.
The aod is almost more common than the c6 these days. They were in most ford diesel 7.3 automatics including the ambulances. They were even used on ford lightnings. Lots of controller kits available it has become a favourite among hot rod guys that want an overdrive. really no bad choice but the extra gear would be nice. you can look up your tires and see what the circumference to figure out how far you travel for every turn of the wheel and then use the gear ratio to calculate the shaft rpm at a given speed. then run it through the trans ratio to figure out what engine speed would be. Bear in mind the math is not finite with a c6 as the torque convertor is not locking up so there is some slip to be accounted for.