U-joints and gas mileage

Hello all, I’ve got an ‘05 Tundra that I bought new and it’s hauled myself and everything imaginable for 19 years. Only 140K miles though, so I’m wondering if anyone else has had u-joints fail at similar mileage? Also, if I’m gonna replace a u-joint, would it make sense to replace them all, or no? There’s also a carrier bearing too, correct? Would this be an expensive job? Dealer or independent mechanic?
Another topic, fuel economy. When the truck was new, around 17mpg city. Now, 14mpg city, and all my driving is done with a pretty lite foot.
I would appreciate your replies or maybe link me to these issues where previously covered.

 

I prefer to replace all the u joints at once - for piece of mind more than anything else. U joints fail in a couple different ways, but not usually from just wearing out. IME, they are usually subject to water intrusion and/or grease displacement or degradation (from the likes of water intrusion). I don't recall whether or not gen 1 u joints are grazable but I think they are sealed. Either way, they live a tough life. If one u joint failed, the rest have usually seen the same conditions. So I just replace them.

And yes, there is a carrier bearing as well. If I'm not doing the work, I prefer a driveline specialty shop. If you can turn a few wrenches and pull the driveshaft, they will rebuild it on the bench and, depending on where you live, usually do it of a fraction of the cost of a dealer. I think I was quoted $300 to have my driveshaft shortened, u joints replaced; the carrier bearing added $150 or so, IIRC.

As for fuel economy, there are a plethora of reasons to see your fuel economy drop. First thing I would ask is, how well have you maintained the vehicle? Has it seen new spark plugs recently? Clean air filter? New PCV valve? Cleaned the MAF? Have you serviced the transmission, transferase (if 4x4), and differential(s)? What about the serpentine belt and tensioner/pulley? Are you running the same size, style, and load rating tire as stock? What do your brakes look like? Have you inspected the pad wear to look for signs of a sticky caliper? All of those things can affect fuel economy. Hope that helps.

 

I believe my first one went bad around 170,000 miles and 8-9 years old then the second one at just over 200,000. Somewhere after the first ujoint I also had the bearing done

So 140,000 and 19 years old doesn't sound unreasonable at all.

I wish I would've gotten it all done at once as @blenton suggested.

 

I'd say you had a good run.

I will also give you advice. Only use Dana/Spicer u-joints when replacing. Use or request a zerked Dana/Spicer joint so you can keep them lubed, then lube at least every other oil change with an appropriate grease per Dana/Spicer's reco. Get a decent grease gun and learn how to use if not already able.

I'd love 14mpg city. I'm lucky to get 11 with my current setup, when I was 100% stock I barely ever hit 14, only with mixed driving. FWIW, I don't keep my foot in the pedal. The fuel tracking app on my phone is a sad sight. It's a sad sight. Be happy you don't have 4WD with slightly oversized tires.

 

So, around mid august last year i noticed my fuel mileage decreasing, so did everyone else around me.
Mom, dad, friends, wife, myself, everyone i talked to all noticed by October they were not getting the same fuel mileage they had prior to September.
By October it was hard to hide, everyone had lost 2-5mpg off their norm.
My moms Rav4 went from 39-40 down to 32-33
My dads Tacoma went from (super light footed driver with 4cyl) 28 down to around 24-25
My 4runner went from 19 down to 16
My Tundra went from 18 down to 15
Everyone else i talked to reported the same.
I dont think we are all getting less fuel mileage due to our vehicles, i am fairly confident they put something in the fuel across the board. Whether its an increase in the Ethanol content or an increase in an additive, something they are putting in the fuel is causing it to burn more fuel to get to the same point. You can easily see a MAJOR difference when you switch to 100% gasoline on our trucks. If i pony up for the expensive Ethanol Free fuel, my mileage increases
My 4runner gets 22-23 and my Tundra gets 20-22 on Ethanol Free fuel
And if you do the math with injector duty cycles, the 8-10% Ethanol blended fuel requires 18% more volume of fuel to be pushed thru the injector to get the same AFR. This is why you see about a -18% reduction in fuel economy when you switch over from 100% gasoline to 10% ethanol blend. Any vehicles built prior to 2008 are tuned on 100% gasoline, pretty much everything after 2008 is tuned for ethanol blend, this is when the big switch was over to ethanol blended fuel. If you remember, war in middle east, sand monkeys cutting oil production, the US gubbamint bombing refineries in the middle east to cut the sand monkeys money and income, so we got in a major pinch and didnt have any fuel so prices went sky high. Then they started pumping Ethanol blended fuel as the next cool thing and here we are with the worst addition to combustion engines we have had in over 100 years.

So i say all that to say this, if you paid attention to the world around you, you likely remember the 2022 gas price increases due to incompetence of the administration around us, followed by the draining of the Strategic Reserves in order to supplement the lack of oil imports. I followed the Strategic Reserve level for a while and watched it dwindle down and then (magically) the levels planed off and stopped falling, and had gains when there were no purchases by the gubbamint to refill. I could tell the numbers were being manipulated so there was no reason to follow along with the levels because clearly someone knew people were watching and started fudging the numbers so we (and other super powers) wouldnt get suspicious. All of this has been said, to implicate, that our gubbamint has likely drained the strategic reserves at bottom of the barrel levels, and likely has increased the ethanol content an additional +10% in our blended fuel without telling anyone. The math says, the loss of fuel economy would be nearly an exact +10% blend in ethanol content, which would require an additional +18% of fuel volume thru the injectors, which would result in an additional -18% in everyones fuel economy. The math checks out, so i am quite suspicious and believe that the pumps are likely more like 20% ethanol blend which is why everyones fuel economy started dropping at the same time. I suspect the additional ethanol blend is supplementing the gasoline because we are running out of fuel.

 

^ To add insult to injury, the powers that be approved an increase in ethanol content to 15% without requiring it be posted at pumps stating 10% ethanol.

 

I wasnt aware of that, but the math says we are likely at 20%.....

 

17 mpg city sounds pretty optimistic. I'm lucky to see that at a steady 65 mph. 14 city seems about right, I've had my 2001 2wd since new, always 14-15 mpg city and around 17 or maybe 18 mpg on the freeway or other steady driving.

 

I have to be honest, that was waaaay too long of a post for me to read so i gave up after the first paragraph. But i 100% agree with that paragraph. I assume that i’ll agree with the rest of what you wrote as well.
And yeah, ethanol made all of my vehicles get worse fuel economy. The government says ethanol is good so the only logical reason would be that all my trip odometers are inaccurate and all the fuel pumps at the gas stations are inaccurate as well.

 

For some enlightenment on the topic of ethanol…

 

It's not just "having it in 2WD". If your truck is 4WD it has hundreds of pounds more weight to lug around naturally, so you're going to get at least a solid 1-2mpg less fuel economy than a 2WD, regardless which mode you run in.

 

I thought it was a pretty good read, i read it twice and it seemed well laid out to me.

 

Summer gas should be here by april.

 

This is the only part of your comment that’s largely correct and there’s probably a good discussion worth having here about. The rest of it, though—I’m in this industry and it’s just not even possible much less true.

 

With these trucks, O2 sensors have the biggest effect on MPG outside of doing modifications to the ride height and wheel/tire weight. You don’t have to have an O2 sensor code to have a sensor that doesn’t operate to its full potential. And a 4wd isn’t just heavier, it also has to spin the front axles constantly, so more unsprung weight and drag. Speaking of drag, poorly adjusted brakes that drag can also rob MPG.

 

Is your tire size original, or have you installed larger size?