Cruiser has a hard time with OD on inclines

[Colairic]

Hey guys,
A brief intro as this is my first post;
I recently bought an ‘04 100 series after quite the extensive search. She’s still just a baby at 120,xxx miles and since purchasing her I’ve dumped thousands into baselining her and getting preventative maintenance under control - timing belt, water pump, spark plugs, coil packs, fuel pump and filter, every single fluid changed out, gaskets and seals, wheel bearings, rotors, pretty much everything.

The vehicle has been absolutely incredible and has already seen thousands of miles in the few months I’ve owned her; but one thing constantly bugs me.

When traveling at interstate speed (60-70mph) and I encounter an incline (like going down I-70 in the mountains) she feels like she really struggles to maintain speed. Even with cruise control engaged, the vehicle will push 45-4700 RPMs just to maintain 65mph on the highway.

Normal driving in the city is completely fine, and the LC has no issues engaging any gear; it just seems like she struggles on inclines. I assume holding near redline for a 5-7 degree grade isn’t normal; so any suggestions on where I should begin?

Tire size is 275/70/18 in case it’s brought up; completely stock otherwise. If this is normal please pardon my arrogance.

TL;DR- 100 series needs to be at 4500+RPMs just to maintain highway speed on a slight incline

 

[geanes]

Seems odd for sure. My 98 (4-speed) with OD off in the mountains can easily maintain 65-70 at 3200-3500 RPMs and I'm on 275/70/18 with a LOT of extra weight.

 

[hoser]

Hmm, I'm not that familiar with I-70 but it would seem normal to me if traveling at 8k+ ft altitude.

Turbo charger would fix that.

 

[Otter]

RPMs sound a bit high, but it depends on what gear you're in, right?

Personally, I never drive in the mountains in OD. I always shift accordingly to keep my RPMs above 3000 on climbs, even if it means being in 2nd gear, and usually don't have a problem maintaining speed. It keeps the transmission from hunting, constantly shifting, and possibly overheating. This is something I did in my 3FE 80 and it just carried over to my 04 100 series.

 

[Colairic]

RPMs sound a bit high, but it depends on what gear you're in, right?

Personally, I never drive in the mountains in OD. I always shift accordingly to keep my RPMs above 3000 on climbs, even if it means being in 2nd gear, and usually don't have a problem maintaining speed. It keeps the transmission from hunting, constantly shifting, and possibly overheating. This is something I did in my 3FE 80 and it just carried over to my 04 100 series.

I could understand being at a little over 3,000 but the LC either wants the redline or she doesn't want to maintain her speed and there is no in between with her on inclines. Whether I'm controlling the throttle and (attempting) to control the gears, or cruise control is doing it for me.

 

[Otter]

I could understand being at a little over 3,000 but the LC either wants the redline or she doesn't want to maintain her speed and there is no in between with her on inclines. Whether I'm controlling the throttle and (attempting) to control the gears, or cruise control is doing it for me.

Gotcha. I am by no means an expert. This is just what works for me.

Hope you get it figured out.

 

[Colairic]

Gotcha. I am by no means an expert. This is just what works for me.

Hope you get it figured out.

Thank you. If nothing else I guess she could go to the stealership but I was hoping to avoid that route.

 

[Mike6158]

I'm in Farmington, NM. KO2's. I think they are 275's but I can't check at the moment. I roam around the 4 corners area plus drive back to TX every now and then. I have to push the OD button on any steep incline otherwise the tranny comes out of OD and drops a gear too. If I catch it before it does that and take it out of OD then RPM on steep hills, at 70-75 mph, is about 3500 at the mosts, if I remember right. If anyone cares to buy me lockers and pay for installing them and 4.88 gears I'll gladly let my LC be a test bed and see if it solves the problem.

 

[dace voit]

When driving in the mountains, at least when going up hills, you should put the transmission in 4th. That should manage the truck pretty well. Steep inclines may require going to 3rd. I don't use cruise control in the mountains, ever. If I could set cruise at 3000 rpms instead of a particular speed for climbing up long hills, that would be great. But alas, the system won't allow me to do that. The system will want to change gears too much. It gets annoying when that is the case. Have you tried just using your foot to control speed instead of cruise? You might loose 5-10 mph or so going up hills but you'll have better control of what the engine/transmission are doing. My truck has the VVT-i motor in it and I still get bogged down on some hills.

How much is the truck loaded down, if at all?

You have to consider that these 7000# tanks are still underpowered, despite getting the 4.7l 8cylinder upgrade from the 4.5l 6cylinder that was in the 80 series and earlier cruisers. Down in Denver, they do well but the altitude gets to them pretty quickly.

 

[Davio6]

Dumb question: Is there Overdrive on these trucks? How do you turn it on?
Thanks,
Dave

 

[DirtDawg]

Dumb question: Is there Overdrive on these trucks? How do you turn it on?
Thanks,
Dave

These trucks have overdrive and it is by default always on. You want to turn it OFF for hills & inclines. I cant speak for the later model years, but on the 4 speed trans, the OD off button is on the side of the shifter.

 

[Davio6]

Thanks DirtDawg.
Dave

 

[saucebox]

These trucks have overdrive and it is by default always on. You want to turn it OFF for hills & inclines. I cant speak for the later model years, but on the 4 speed trans, the OD off button is on the side of the shifter.

For the later models, just move the shifter to 4.

 

[sharkCamo]

My 2004 doesn't have overdrive, but you keep it out of 5th gear by moving the lever over from D to 4. The manual recommends this for towing or high loads.

Edit: ninja'd by saucebox

 

[Colairic]

When driving in the mountains, at least when going up hills, you should put the transmission in 4th. That should manage the truck pretty well. Steep inclines may require going to 3rd. I don't use cruise control in the mountains, ever. If I could set cruise at 3000 rpms instead of a particular speed for climbing up long hills, that would be great. But alas, the system won't allow me to do that. The system will want to change gears too much. It gets annoying when that is the case. Have you tried just using your foot to control speed instead of cruise? You might loose 5-10 mph or so going up hills but you'll have better control of what the engine/transmission are doing. My truck has the VVT-i motor in it and I still get bogged down on some hills.

How much is the truck loaded down, if at all?

You have to consider that these 7000# tanks are still underpowered, despite getting the 4.7l 8cylinder upgrade from the 4.5l 6cylinder that was in the 80 series and earlier cruisers. Down in Denver, they do well but the altitude gets to them pretty quickly.

I haven’t tried just leaving it in fourth; and it is something I will try; but I’ve tried putting her into fourth then back to OD and she just seems to want to stay up at the higher RPMs. I almost never use cruise control even out of the mountains it was more just to see if it was something I was doing or if the computer would do the same thing. No load on her besides the unsprung weight of the larger LT tires which seems pretty insignificant considering what some people are running. Maybe my problem was putting it back into O/D prematurely.

I’ll try just keeping it in 4th tomorrow when I’m out and hopefully that does it.

Thanks for the input guys

 

[Otter]

I’ll try just keeping it in 4th tomorrow when I’m out and hopefully that does it.

Thanks for the input guys

Don't be afraid to drop it into 3rd or 2nd if RPMs drop below 3k and it starts to feel like the engine is lugging. Between 3k and 4k is a bit of a sweet spot, whatever gear you're in.

 

[rival1]

Does your truck have the ect power, switch if so turn it on it changes the shift points.

 

[dace voit]

I haven’t tried just leaving it in fourth; and it is something I will try; but I’ve tried putting her into fourth then back to OD and she just seems to want to stay up at the higher RPMs. I almost never use cruise control even out of the mountains it was more just to see if it was something I was doing or if the computer would do the same thing. No load on her besides the unsprung weight of the larger LT tires which seems pretty insignificant considering what some people are running. Maybe my problem was putting it back into O/D prematurely.

I’ll try just keeping it in 4th tomorrow when I’m out and hopefully that does it.

The transmission is programmed to stay in the higher revs longer compared to the 4 speed I had in my 80, which is the same as the early 100's(A343F, IIRC). My 80 would try to shift up as soon as it could when turning overdrive(4th) back on. My 100 will hang out in the lower gear until a certain amount of time passes when the engine isn't sensing increased load from, say, climbing a hill, despite having shifted up. It's actually a good bit of engineering by Mr. T. Keeping the revs higher makes for smoother driving and is easier on the transmission. It seems strange at first but improves the drivability of the truck up here in the mountains.

 

[Colairic]

Does your truck have the ect power, switch if so turn it on it changes the shift points.

Unfortunately it doesn’t help; the LC stays between 4500 and redline.

The transmission is programmed to stay in the higher revs longer compared to the 4 speed I had in my 80, which is the same as the early 100's(A343F, IIRC). My 80 would try to shift up as soon as it could when turning overdrive(4th) back on. My 100 will hang out in the lower gear until a certain amount of time passes when the engine isn't sensing increased load from, say, climbing a hill, despite having shifted up. It's actually a good bit of engineering by Mr. T. Keeping the revs higher makes for smoother driving and is easier on the transmission. It seems strange at first but improves the drivability of the truck up here in the mountains.

Perhaps what I’m experiencing is normal. Just seemed odd to me that the vehicle would work itself so hard just to maintain its speed. Then again I’ve never owned a heavy, underpowered vehicle to know how it would behave under the stress of an incline at interstate speed.

 

[hoser]

At 10k ft, you'll be down 30% power. Use your shifter to control gear selection, that's what it is primarily for (and braking).