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Topic: Transmission Swap C6 to AT545 (Read 2046 times) previous topic - next topic

Re: Transmission Swap C6 to AT545

Reply #25 –
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
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Transmission Swap C6 to AT545

Reply #26 –
[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.
1986 36' Grand Villa OREG converted to 7.3 IDI diesel

Re: Transmission Swap C6 to AT545

Reply #27 –
Quote from: Flopsie –
[quote author=Pierce & Gaylie Stewart link=msg=276476 date=1497645226
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
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Transmission Swap C6 to AT545

Reply #28 –
Quote from: Pierce & Gaylie Stewart –
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.
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.
1986 36' Grand Villa OREG converted to 7.3 IDI diesel

Re: Transmission Swap C6 to AT545

Reply #29 –
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.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean
 

Re: Transmission Swap C6 to AT545

Reply #30 –
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.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


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