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Topic: Transmission Slipping?? (Read 7 times) previous topic - next topic
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Transmission Slipping??
Yahoo Message Number: 23908
Friends just drove our LD with 28,000 miles over the Sierras to Las Vegas.  As they climbed the mountains the transmission began to slip....first on steep hills...then on a lesser hills.
Transmission fluid was showed full.

A couple times the "check engine" light came.  It has never come on before.  They stopped for awhile.  Apparently things cooled off because they didn't have any slipping for the last hour to LV...of course it was mostly downhill.

Any diagnosis that won't make me really sad?

Thanks
Re: Transmission Slipping??
Reply #1 –
Yahoo Message Number: 23995
Quote
Friends just drove our LD with 28,000 miles over the Sierras to Las Vegas.  As they climbed the mountains the transmission began to slip....first on steep hills...then on a lesser hills.
Transmission fluid was showed full.
Two things come to mind here, both are not terminal problems.  When was the last time you changed the fluid?  If it's been over 15k miles, you need to change the fluid.  Some people change it every year.  Your tranny does a lot of work, especially in mountains, even more on a hot day in the mountains.  Old/dirty fluid will not be up to the task.
The other thing that comes to mind is heat.  If it was a hot day that day, which it probably was, that would cause that to happen as well.
Did your friend leave the tranny in OD?  If he did, that would cause the tranny to shift much more, which would cause the tranny/tranny fluid to overheat.  There may have been some grades where he should have been in 2nd, but had it OD or 3rd.  Again, this would cause the tranny to shift more than it should.

In any case, I would do a 100% fluid change and replace the tranny filter.

Well, that's my diagnosis.  Hope that helps.

-Victor
Re: Transmission Slipping??
Reply #2 –
Yahoo Message Number: 24000
Quote
Any diagnosis that won't make me really sad?
I don't know which chassis you have, what I am suggesting applies to the Chevy, and possibly to the Ford.
 Now, how do you know the tranny was slipping (do you have a tach)? A common confusion occurs when the engine fan clutch begins to activate as the load and engine temps increase. The sound is a 'revving up' that can sound a lot like the engine speeding up when in fact it is not. Particulary on newer engines, the fan clutch cycling in may be infrequent enough that short-time owners are unfamiliar with the experience.

Steve
2004 FL
2013 Honda Fit
Re: Transmission Slipping??
Reply #3 –
Yahoo Message Number: 24253
Quote
...As they climbed the mountains the transmission began to slip....first on steep hills...then on a lesser hills.
A couple times the "check engine" light came.  It has never come on before.  They stopped for awhile.  Apparently things cooled off because they didn't have any slipping for the last hour to LV...
What year LD is it?

I just had a similar experience coming back from a trip from Milwaukee WI, back to Texas over the 4th of July week.  I didn't have the check engine light come on, I have an '84 so I don't think it even has one.

My symptoms were similar, it was cruising along just fine, and then when the heat of the day increased, the engine temp started to creep up, gauge went from about 140 to about 160-165, then on hills it started to feel like the tranny was slipping. If I turned the A/C off it improved, which made me suspect it wasn't the tranny. If I slowed down about 5 mph that would eliminate the problem too. When I stopped for gas, I checked the tranny fluid level, it was perfect. I filled the gas tank with (cool) premium gas, and didn't have a problem for over an hour, and then it started again when I'd go up hills.  Once I got into Texas (relatively flat) there were no problems the rest of the way.

Anything is possible, but I don't think it's the tranny.  I think it's a loss of horsepower at high temperature, and the engine starts lugging up hills.  Looking at my '84 there are a lot of things that could be improved for high temp driving.  The air intake isn't cold air, it's just engine compartment (hot) air.  The fuel lines run very close to the exhaust manifold (hot fuel isn't as dense as cool fuel so it doesn't produce as much horsepower), and of course it has a mechanical fuel pump, not electric, so it's possible the hot fuel was even vapor locking a little (unlikely though, my experience with vapor looking is that once it happens, it just stops you dead until it cools off). I think I remember reading that horsepower decreases about 2-3% for every 10-11 degrees (F?) of intake air temperature increase.  So if it's 90 degrees out, and the underhood temp is over 200 that's easily a 10% hp loss.
 I'm going to be making this trip again in August, so it might even be hotter.  I'm planning on adding an electric fuel pump and a new Stewart water pump (not because of this problem, I was planning on doing these anyway), possibly putting a heat shield around the fuel line past the exhaust manifold, and looking into seeing if there are aftermarket "cool air" kits for getting some fresh air to the carb.
Of course, just to be safe, I'll take it in for a tranny checkup/fluid/filter change.

Let us know if you get your problem diagnosed.

Chuck.
Re: Transmission Slipping??
Reply #4 –
Yahoo Message Number: 24269
Quote
...As they climbed the mountains the transmission began to slip....first on steep hills...then on a lesser hills.
A couple times the "check engine" light came.  It has never come on before.  They stopped for awhile.  Apparently things cooled off because they didn't have any slipping for the last hour to LV...

What year LD is it?

I just had a similar experience coming back from a trip from Milwaukee WI, back to Texas over the 4th of July week.  I didn't
have

The thermo-clutch engine fan on these engines will sound like an F- 104 Phantom on carrier takeoff when it engages fully. With partial engagement, it will sound like the engine is trying to rev up, as though the tranny is slipping. These fans can consume as much as 40 hp at max engine rpms, 1/4 of your available pulling power. You will most definitely feel it - and it is normal.

Steve
2004 FL
2013 Honda Fit
Re: Transmission Slipping??
Reply #5 –
Yahoo Message Number: 24304
Quote
The thermo-clutch engine fan on these engines will sound like an F- 104 Phantom on carrier takeoff when it engages fully. With partial engagement, it will sound like the engine is trying to rev up, as though the tranny is slipping. These fans can consume as much as 40 hp at max engine rpms, 1/4 of your available pulling power. You will most definitely feel it - and it is normal.
Wow, I had always heard that the fan sucks horsepower, but I never saw a figure (40 HP) for it!  I see a lot of discussion on RV groups about electric fans, I guess that's why there's debate.
 On the tranny slipping thing, for me, it wasn't so much the sound as it was the feeling that is was slipping, sort of a rythmic lurching of the LD as it went up the hill. Between the HP loss due to the fan, the losses to heat, I wonder how much of the measley 155 or so horsepower is left for pulling the LD up the hill! From the manual I have (Chilton), the '83-'86 Chevy 350's with a 4-Barrel produced 165 horsepower @ 3800 RPM, and 275 ft. lbs. of torque at 1600 RPM. For the California emission version, which I have, it's even worse: 155 HP @ 4000 rpm, 240 ft lbs @ 2800 rpm.  These numbers are SAE numbers (which means that all the accessories were on and it was measured coming out of the tranny).  But I bet the SAE numbers don't account for heat loss and I bet the thermo-clutch fan isn't fully engaged.
 One other interesting (to me anyway) thing is that when I slowed down to 50 mph it stopped lurching, my tach read about 2800 rpm, I didn't realize it at the time, but this is  the perfect rpm for max torque for my engine (240 ft-lb @ 2800 rpm).  So for me, I guess keeping the rpm around 2800 will help me up hills.

I guess an older RV always gives you something to think about!

Chuck.