Buying 85 IDI ATS turbo motorhome!

[Cubey]

In my experience, C6s gain a lot of speed on steep down hills if you don't downshift. Both my F250 and RV are like that, and the F250 has a newer rebuilt C6 so I suspect that's just how they are in general.

On these basically 1 lane gravel forest service roads, I don't go much over 15mph due to the occasional dips/ruts, and how much dust it kicks up.. which finds it's way inside the RV and sets off the smoke detector! On the way out of the last camp yesterday, I had to stop and take out the battery because I got up to like 25 on a smoother part of the road and it set it off due to the dust. Happened at Lake Mead too. So, downshifting manually is a must, or I'd be going 40mph on a rough 1 lane gravel road in a 27ft motorhome pulling a cargo trailer.

Maybe they have to get below a certain speed before they can downshift? But I'm not sure about that. Pretty sure my F250 does at any time, but I could be mistaken. I took it on some very back country gravel roads in Colorado. One, Phantom Canyon Rd, was basically me coasting down the side of a mountain in 1st gear (occasionally in 2nd) along what is an old railroad route to Cripple Creek.

Sometimes I downshift the RV to 2nd on interstates in places where it's a steep down grade (where they warn semis) since it likes to do nothing but gain speed. It's easy to burn up the brakes if you aren't careful. I did that a bit on the F250 in CO (before Phantom Canyon) before I knew you could/are supposed to downshift. Plus the linkage was hanging up and wouldn't let me put in 1st. I got it sorted out though and used it a lot, especially around Grand Teton/Yellowstone on those narrow 2 lane highways with 25mph limits with steep grades and curves.

 

[IDIBRONCO]

Maybe they have to get below a certain speed before they can downshift? But I'm not sure about that. Pretty sure my F250 does at any time, but I could be mistaken.

There is a point where they won't downshift even manually. You won't be able to shift into first at 45 MPH.

 

[Farmer Rock]

My knowledge of automatic transmissions is very limited, but I do have to agree with @IDIBRONCO about them not downshifting over a certain speed. Every auto I have driven, would need to be slowed down before it down shifted, especially if going down hill.



Rock

 

[Cubey]

I wonder if it's a governor issue. This thread sounds similar, although mine doesn't jump from 1 to 3, but it has the late shifts, odd downshifts to second by itself when coasting/braking and it gets around 30mph, occasional staying in second unless at a complete stop.. and now it perhaps hanging and not quite downshifting to first at complete stops.

https://www.ford-trucks.com/forums/41827-c6-governor.html

 

[71 Highboy]

In my experience, C6s gain a lot of speed on steep down hills if you don't downshift. Both my F250 and RV are like that, and the F250 has a newer rebuilt C6 so I suspect that's just how they are in general.

On these basically 1 lane gravel forest service roads, I don't go much over 15mph due to the occasional dips/ruts, and how much dust it kicks up.. which finds it's way inside the RV and sets off the smoke detector! On the way out of the last camp yesterday, I had to stop and take out the battery because I got up to like 25 on a smoother part of the road and it set it off due to the dust. Happened at Lake Mead too. So, downshifting manually is a must, or I'd be going 40mph on a rough 1 lane gravel road in a 27ft motorhome pulling a cargo trailer.

Maybe they have to get below a certain speed before they can downshift? But I'm not sure about that. Pretty sure my F250 does at any time, but I could be mistaken. I took it on some very back country gravel roads in Colorado. One, Phantom Canyon Rd, was basically me coasting down the side of a mountain in 1st gear (occasionally in 2nd) along what is an old railroad route to Cripple Creek.

Sometimes I downshift the RV to 2nd on interstates in places where it's a steep down grade (where they warn semis) since it likes to do nothing but gain speed. It's easy to burn up the brakes if you aren't careful. I did that a bit on the F250 in CO (before Phantom Canyon) before I knew you could/are supposed to downshift. Plus the linkage was hanging up and wouldn't let me put in 1st. I got it sorted out though and used it a lot, especially around Grand Teton/Yellowstone on those narrow 2 lane highways with 25mph limits with steep grades and curves.

It could be a sticky spool in the valve body. A good quality kit will allow manual shifting up or down at any REASONABLE speed, i.e. matching gear to road speed. I manually shift regularly, up and down, using second gear for downgrades, and even on a 5% grade will have to feed light throttle or it will slow too much. In 3rd, it will gain speed requiring brakes. Make sure the valve on the pump is adjusted properly also. A dimes width on this adjustment makes a big difference in how it shifts and when it shifts. There is a fine balance between this valve and the modulator on the trans. When set properly by trans pressure/ vaccume, the shift should be hardly felt on light throttle, and go to redline in each gear on hard throttle.

 

[Isaac Ristow]

To me sounds like low pump pressure at idle. I would hook a pressure gauge to the port on the side see what pressure it makes hot at idle. Likely a leaking shift servo or a weak pump. I know how transmissions work but I'm not a expert. Also if you want to eliminate the vac as probable cause but not likely just unhook vac to the vrv once it will shift very late and hard but eliminates it because too much vacuum to them makes them slip and upshift way too soon

 

[Cubey]

To me sounds like low pump pressure at idle. I would hook a pressure gauge to the port on the side see what pressure it makes hot at idle. Likely a leaking shift servo or a weak pump. I know how transmissions work but I'm not a expert. Also if you want to eliminate the vac as probable cause but not likely just unhook vac to the vrv once it will shift very late and hard but eliminates it because too much vacuum to them makes them slip and upshift way too soon

It could be at it's age. I'm considering getting a bottle of Lucas trans fix and putting in half a bottle to see if it helps, then draining the pan and replacing the fluid after the seals in the trans have had time to swell up. That's what this transmission tech suggests in this video:

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[Cubey]

On another subject, I think I'll get the $300 in tools (vac pump and AC gauge manifold) from O'Reilly and see if the in dash ac will hold vacuum. It has a VERY tiny of pressure still in it, when i hooked the singe hose gauge (for refilling, like stores sell for about $12) an opened the valve on it. It was a VERY faint hiss so I quickly closed it again. It could have been last charged 20 years ago and just naturally lost it over time. For the $10 for vac pump oil, I can at least test the system to see if it'll hold the refrigerant.... assuming I can get it. For some stupid reason, O'Reilly refuses to keep the stuff in stock at most stores.. even ones that have the tool. So you can't even the tool! I'd have to call days ahead and have it sent there. Really stupid.

Or just get some $5 Walmart cans of refrigerant and refill it as-is. Might just do that, honestly. I want/need in-dash AC for when I'm driving in summer, even when I try to chase temps under 80 degrees. Can't always avoid it, like next week it's gonna be around 88-90 when I need to put a couple hundred miles behind me. It's 100 miles to the next Walmart but if I can recharge it for the enxt day when I need to go 100+ miles again, it would be nice for the $30 in refrigerant. If it has a tiny leak and needs it every few years like my F250, so be it.

 

[gnathv]

Does your motor home have the big York compressor on it?

 

[Cubey]

Does your motor home have the big York compressor on it?

No, FS6 or 6E171, not sure what the difference is:

https://www.oreillyauto.com/shop/b/...d-e-250-econoline-club-wagon?q=a/c+compressor

You must be registered for see images attach

 

[Cubey]

Ehh, I think I'll just get some $5 cans of R134a and try charging it. If it doesn't show any improvement after the first can, I'll give up and return the rest. The AC compressor clutch engages in AC mode and disengages in fan mode, so I guess it has just enough pressure still to make it turn on, but for some reason not enough to show on the cheap refill hose/gauge I have. It does have SOME pressure if I poke the low pressure side valve with a screw so it's not totally empty, and an yellow oily substance comes out. So, at least I know it hasn't totally gone to air. It's probably like my F250 where it just needed a recharge due to a very slow leak. 2 cans worked on the F250 but the RV might need 3-4. I do wish I had a longer hose since the low pressure side fitting it a bit hard to get at, but oh well.

EDIT: Duh, I can get the loaner hose/gauge set from an auto parts store for filling so it won't be so difficult with the short cheapy one.

 

[Booyah45828]

In order to get an accurate idea of system operation, you should be looking at both high and low side pressures when adding those cans. I've seen people with plugged orifice tubes add can after can of r134a, because the gauge on the can was still reading low, only to blow the pressure relief on the compressor due to being overcharged.

 

[Cubey]

In order to get an accurate idea of system operation, you should be looking at both high and low side pressures when adding those cans. I've seen people with plugged orifice tubes add can after can of r134a, because the gauge on the can was still reading low, only to blow the pressure relief on the compressor due to being overcharged.

Well, I already charged it with 4x 12oz cans with the single hose and it's blowing cold. The capacity is something like 56oz I read online. I checked how cold it was after each can. It was blowing HOT after 100 miles of driving earlier before I started filling. The first can made a small difference. After 3rd can it wasn't quite there so I put in the forth. So far, so good, for the 6 miles or so city driving I have done since I did it a few hours ago. Nice and cold. It's probably been 20 years since it was charged. It wasn't driven much for probably that long nearly when I bought it 2.5 years ago.

 

[Big Bart]

In my experience, C6s gain a lot of speed on steep down hills if you don't downshift. Both my F250 and RV are like that, and the F250 has a newer rebuilt C6 so I suspect that's just how they are in general.

On these basically 1 lane gravel forest service roads, I don't go much over 15mph due to the occasional dips/ruts, and how much dust it kicks up.. which finds it's way inside the RV and sets off the smoke detector! On the way out of the last camp yesterday, I had to stop and take out the battery because I got up to like 25 on a smoother part of the road and it set it off due to the dust. Happened at Lake Mead too. So, downshifting manually is a must, or I'd be going 40mph on a rough 1 lane gravel road in a 27ft motorhome pulling a cargo trailer.

Maybe they have to get below a certain speed before they can downshift? But I'm not sure about that. Pretty sure my F250 does at any time, but I could be mistaken. I took it on some very back country gravel roads in Colorado. One, Phantom Canyon Rd, was basically me coasting down the side of a mountain in 1st gear (occasionally in 2nd) along what is an old railroad route to Cripple Creek.

Sometimes I downshift the RV to 2nd on interstates in places where it's a steep down grade (where they warn semis) since it likes to do nothing but gain speed. It's easy to burn up the brakes if you aren't careful. I did that a bit on the F250 in CO (before Phantom Canyon) before I knew you could/are supposed to downshift. Plus the linkage was hanging up and wouldn't let me put in 1st. I got it sorted out though and used it a lot, especially around Grand Teton/Yellowstone on those narrow 2 lane highways with 25mph limits with steep grades and curves.

I find the C6 works a little different than other tranny's. When you put it in 2nd gear and you start to accelerate from 0mph you are starting out in second gear and staying in second gear. When you slow down or stop it still stays in 2nd gear. Unlike other trannys that limit to no further that 2nd gear, they actually start in first, then go to second, and go back to first as you slow down. So, if you want first gear in a C6 IDI you need to move the gear selector to 1st.


I notice going down grades my truck will go faster at the same RPM. (70mph instead of 65mph.) I believe (Not saying I am correct.) that is because the C6 does not have a lock up torque converter. So, if the vehicle is going uphill the torque converter is working at say 90% efficiency. (Loses some efficiency.) The crank and tranny do not turn at the same speed. Rather the tranny turns at say at 90% the speed of the crankshaft.) But going downhill the torque converter is now working at 110% efficiency. (The tranny is going 10% faster than the crankshaft.) The inner torque converter fan (Hooked to the tranny.) is now spinning faster than the outer fan (Hooked to the crank.), and the inefficiency becomes efficiency. The tranny now turning faster but being held back because the crankshaft that is not turning as fast. But the inefficiency of ATF transfer allows for some slip and let’s the tranny turn say 10% faster than the crank.


So, the vehicle starts to go 3-8mph faster at the same RPM, because the torque converter is not locking the crank and tranny to the same speed. Rather the tranny is running at faster than crank speed (The truck is being pulled down the grade by gravity.) because there is a small gap between fans, energy is not being transferred at 100% and the tranny is now working at 110% of the crank’s intention.


So, you will experience an increase in MPH at the same RPM. I do not recall if my truck outside of this wants to increase speed by any significant amount when I let off the accelerator and have a load or trailer in tow. I will have to watch on my next Jeep trip when coming down a grade how much it speeds up. (I too often just leave the truck in 2nd because the speed limit is often 45mph or less.) My issue is generally not having a turbo, I end up in 2nd gear going only 40-45mph up the hills.

 

[IDIBRONCO]

I find the C6 works a little different than other tranny's. When you put it in 2nd gear and you start to accelerate from 0mph you are starting out in second gear and staying in second gear. When you slow down or stop it still stays in 2nd gear. Unlike other trannys that limit to no further that 2nd gear, they actually start in first, then go to second, and go back to first as you slow down. So, if you want first gear in a C6 IDI you need to move the gear selector to 1st.


I notice going down grades my truck will go faster at the same RPM. (70mph instead of 60mph.) I believe (Not saying I am correct.) that is because the C6 does not have a lock up torque converter. So, if the vehicle is going uphill the torque converter is working at say 90% efficiency. (Loses some efficiency.) The crank and tranny do not turn at the same speed. Rather the tranny turns at say at 90% the speed of the crankshaft.) But going downhill the torque converter is now working at 110% efficiency. (The tranny is going 10% faster than the crankshaft.) The outer torque converter fan (Hooked to the tranny.) is now spinning faster than the inner fan (Hooked to the crank.), and the inefficiency becomes efficiency. The tranny now turning faster but being held back because the crankshaft that is not turning as fast. But the inefficiency of ATF transfer allows for some slip and let’s the tranny turn say 10% faster than the crank.


So, the vehicle starts to go 3-8mph faster at the same RPM, because the torque converter is not locking the crank and tranny to the same speed. Rather the tranny running at faster than crank speed (The truck is being pulled down the grade by gravity.) because there is a small gap between fans, energy is not being transferred at 100% and the tranny is now working at 110% of the crank’s intention.


So, you will experience an increase in MPH at the same RPM. I do not recall if my truck outside of this wants to increase speed by any significant amount when I let off the accelerator and have a load or trailer in tow. I will have to watch on my next Jeep trip when coming down a grade how much it speeds up. (I too often just leave the truck in 2nd because the speed limit is often 45mph or less. My issue is generally not having a turbo, I end up in 2nd gear going only 40-45 up hills.

That's a much better explanation than I could have given. Although it's not just C6s that work this way (at least as far as the uphill/downhill part is concerned). I believe that it's any automatic transmission without a locking convertor. The FMX in my Red Truck does the same thing. Granted, the C6 is the only one like this that came behind our IDI engines.