What should I do, or un-do next?

[sawblade999]

I’ve been reading threads all day and it looks like I’ve done some smart things, and some not so smart things. I obviously need some help.

I have a 2002 Tundra AC 4X4 with the 4.7L engine. I pull a 27 ft. fifth wheel trailer weighing about 7500 lbs. I’ve already done the following modifications:

K&N FIPK intake
Cat back Flowmaster 70 series muffler and dual side exit exhaust.
Auxiliary ATF cooler and temp gauge, with Mobile 1 ATF
Firestone ride-rite air bags

I’m having a problem with power and gas mileage. On a recent trip to Disneyland we had to climb the infamous “grape vine”. The truck bogged down to 30 mph in second gear and had a difficult time making the summit. My average towing mpg at 60 mph with OD off was 8.2, and we barely got 7 mpg on the grape vine segment.

I’ve been trying to figure out how to improve towing power and gas mileage and have seen recommendations for everything from adding RAPS to the K&N, returning to the stock air intake, add a supercharger, order a unichip, headers, rear gears, and a few others things.

Does anyone have a good set of mods or a “package” approach to this problem, or am I already getting as good as I can get? Thanks in advance for any and all suggestions.

[boody]

7500lbs. is to heavy for a tundra no matter what you do or undo.

[mustang67408]

There isnt anyting you can do to that TUNDRA to make it pull that trailer.
Short of buying a BIG FORD/CHEVY/ or DODGE.
The tundra just doesnt have the GVWR needed for that.
A S/C might help pull it, but you'll be straining it no matter what.
Gears may even help,The rest of the truck just isnt built for that.
The airbags are just for support and they offer no additional weight carrying capacity.
ITS JUST TOO HEAVY!!!


Best thing to do is BUY a lighter trailer.Just my $.02

[dyogim]

What about headers from JBA? Another option in regards to regearing is 4.30 gearsets. Downfall is that they are hard to come by. Dealer wants $600 for a set. You might be able to find a set for a fraction of that cost.

Tranny upgrade-Talk to Jon at IPTtrans.com to help build up your tranny and offer any suggestions.

In the future, I plan on building up my tranny with the rebuild kit Jon offers and have him modify the valve body. Also thinking about having the planetary gears cryo'ed. I have a 2000 4WD V8. Bought new in July 2000 and have 72000 miles. Check out my pics in the Engine and Drivetrain album to see what happened to my tranny. Anyways, I'm located right next door to you in Pittsburg if you ever what to check it out.

[sprj8008]

I had my 20 foot fifth wheel on the scale this weekend. Only had 40 pounds spare capacity on the rear axle. That's only a 4000 pound trailer.

I have a supercharger, intake, exhaust and IPT. I wouldn't put a bigger trailer back there. I can pull it at 80 miles an hour if I want. It's not a power issue.

I instead pull at 60 mph and get 12 mpg. It's work for this little truck. I only put about 3000 miles a year with the trailer, so I make due. It's a beautiful truck empty.

I think I'd make sure I was in front of a 27' trailer on a tundra if I saw it coming. Probably not what you wanted to hear.

Good Luck. Jason.

[KLS]

Sawblade,
Your choice...put more money in to the Tundra which is seriously overloaded and will never tow that trailer reliably, or save for more truck. You NEED at least a 3/4-ton truck for that trailer.

Your options at this point are few. Changing to 4:56 differential gears is about the best thing you can do. It will hurt your unloaded mileage, but will help you loaded power and reduce the strain on the drivetrain.


Ken

[sawblade999]

OK, unless I’ve really screwed something up I know I am over weight by about 166 lbs. I used several calculators found on various web sites, and what I think are generous weights for the way we travel. Here’s what I came up with.

Truck curb weight 4501lbs (from Toyota spec sheet)
Cargo weight 700 lbs (that’s fuel, 2 people, 5th wheel hitch, and misc. stuff)
Max Gross Trailer Weight rating 7000 lbs (from Toyota owners manual)
CGWR 11800 lbs (from Toyota owners manual)

Trailer dry weight 6015 lbs (from manufacturer spec sheet)
Trailer cargo 750 lbs (water, propane, food, cloths, TV, misc. stuff)

The gross trailer weight of 6765 is 235 under the allowed weight of 7000 lbs., but the total Combined Gross Weight is 11966 lbs. With a truck CGWR of 11800 lbs, that’s 166 lbs over weight. I think Toyota engineers are stingy with their weight ratings, but be that as it may, I’ll cop to the overweight condition. That’s why I added the ride-rite air bags.
Sorry I miss represented the weight as 7500 lbs in my original post. I guess I thought any solution for a nice fat 7500 lbs would be even better for my actual weight. Be assured I will take the rig to the scales and verify all this next time we are out.

Now, if I am still in your good graces, are there any viable solutions to my power and gas mileage problem? Thanks for the SC, gear, and tranny suggestions.

[mustang67408]

My 2002 tundra weighs 6200 lbs GVWR
I think you used the wrong number to figure out your carry capacity

11800 cgwr of truck and trailer
6200 gvwr of truck
--------------(subtract)
5600 lbs is all that tundra should tow (capacity)

The trailer dry(yours) is about 415 lbs to heavy empty, buy the time you add cargo, water, fuel, passengers, food ECT.... your almost 1500lbs to heavy.
I think RAY or KEN need to help you out with your numbers. To me its just way to heavy.

[RockyMtnRay]

Originally Posted by sawblade999

OK, unless I’ve really screwed something up I know I am over weight by about 166 lbs. I used several calculators found on various web sites, and what I think are generous weights for the way we travel. Here’s what I came up with.

Truck curb weight 4501lbs (from Toyota spec sheet)
Cargo weight 700 lbs (that’s fuel, 2 people, 5th wheel hitch, and misc. stuff)
Max Gross Trailer Weight rating 7000 lbs (from Toyota owners manual)
CGWR 11800 lbs (from Toyota owners manual)

Trailer dry weight 6015 lbs (from manufacturer spec sheet)
Trailer cargo 750 lbs (water, propane, food, cloths, TV, misc. stuff)

The gross trailer weight of 6765 is 235 under the allowed weight of 7000 lbs., but the total Combined Gross Weight is 11966 lbs. With a truck CGWR of 11800 lbs, that’s 166 lbs over weight. I think Toyota engineers are stingy with their weight ratings, but be that as it may, I’ll cop to the overweight condition. That’s why I added the ride-rite air bags.
Sorry I miss represented the weight as 7500 lbs in my original post. I guess I thought any solution for a nice fat 7500 lbs would be even better for my actual weight. Be assured I will take the rig to the scales and verify all this next time we are out.

Generally the problem with 5th wheels isn't the GCWR (which you seriously exceeding BTW) but the Gross Axle Weight Rating (rear). The rear axle on your truck is rated for only 3760 lbs. With a 6800 lb 5er trailer (probably closer to 7100 lbs since trailer dry weights don't include any options (like AC, spare tire, etc.)), you've got roughly 20% of that weight (or about 1400 lbs) sitting on the truck's rear axle. When you calculated your truck's actual weight, you forgot the weight of all the options you have...such as air conditioning, even the spare tire....(options...even the standard ones...are not included in the published "curb weight") and usually add up to at least 300 lbs. I've had my truck weighed at an RV safety weigh-in and even without a 5th wheel hitch in the bed and with only 1 person and little cargo, the weight on the rear axle was about 2700 lbs. Since you do have the 5th wheel hitch...and more cargo and a passenger...the weight on your rear axle before you hookup the trailer is likely around 3000 lbs. Add 1400 lbs of pin weight and your rear axle is at least 700 lbs overloaded. That's a huge overload. It doesn't matter that you've added airbags because beefing up the suspension doesn't address the fact that the axle itself is only a slightly widened Tacoma axle and the differential is a Tacoma differential. People have actually snapped the rear axle at the spring mounts as well as breaking the rear frame. A goodly number of people here have broken the spider gears in the differential...which typically grenades the entire differential and axle. A few thousand miles of towing on rough roads could produce enough repititive metal fatigue to result in your axle breaking.

As for the GCWR, you're actually around 500 lbs overweight once you factor in the weight of the options. Percentage wise this isn't as bad as the overloading of the rear axle but it is still contributing to the crappy towing performance. Incidentally, the Grapevine isn't all that big a challenge...yes, it's moderately steep but it's also quite low altitude (under 5000 feet). If your truck was down to 30 mph on that, try to visualize how slow (5 mph? 10 mph?) you'll be on a crossing of the Sierra or the Rockies (I routinely tow across passes as high as 12,000 feet above sea level).

Now, if I am still in your good graces, are there any viable solutions to my power and gas mileage problem? Thanks for the SC, gear, and tranny suggestions.

First of all, two of the mods you've made (K&N FIPK, Flowmaster with dual outlets) are the worst possible things you could have done for towing performance. Both of these mods severely reduced your mid range torque. Yeah, they might have given you a little top end horsepower but top end horsepower doesn't move a trailer...torque (at around 3000 RPM) is what moves a trailer. Therefore, IMMEDIATELY put the stock intake back in and replace the FlowRestrictor muffler and torque-killing dual pipes with the stock exhaust. Those two changes alone will return about 20 ft-lbs of mid range torque.

Forget the supercharger...they're very expensive ($5000 installed) and nearly impossible to buy since they're no longer sold. Even if you can find one, I think you'd be taking a real risk with your engine's longevity if you had a supercharger and tried to tow that monster trailer.

Transmission modifications will firm up your shifts but won't do thing for the lack of power. If you're driving as you should be (OD off), you shouldn't be having that many power on shifts anyway. IOW, IMO, transmission mods are a waste of money for towing.

Regearing your axle to 4.30 gears will substantially improve (by 10%) your rear wheel torque. I did exactly that and can testify it's the most effective mod for towing. But it will also cost you around $1200 for the rear axle alone.

Installing JBA...or TRD...headers will improve your midrange torque by about 7% (roughly 23 ft-lbs). Headers were my first mod to increase towing torque and they made a very noticeable difference in mountain towing.

Finally, once you have the single stock exhaust pipe back on the truck (it's 2 3/8 inch diameter is perfect for optimizing mid range torque), you can get about another 3% gain in torque (~10 ft-lbs) by replacing the stock muffler (muffler only) with a Gibson 788500S muffler (24 inch muffler body). Gibson mufflers are very quiet and are the only aftermarket muffler designed specifially to improve mid range towing torque instead of top end horsepower.

The bottom line is your trailer is just plain way too heavy for your truck. Even if you get rid of the crappy-for-towing intake and exahust...and install headers that are optimized for low-RPM torque (don't use SS Autochrome) as well as a best-for-towing Gibson muffler...and regear the differential...you'll still have a truck that doesn't have enough torque or structural strength for that trailer. It'll perform a heckuva lot better on moutain grades than it does now (I can tow my 4000 lb trailer up 5% grades at 11,000 feet without having downshifts!). But you still will be grossly overloaded. There are only two "proper" solutions...trade the truck for a domestic 3/4 ton truck or trade the trailer for a much lighter (like about 3000 lbs lighter) trailer. If you keep towing that too-heavy trailer, your truck's lifespan is going to be severely shortened and a catastrophic failure of the axle is a distinct possibilty.

[sawblade999]

Ray, (and everyone else)

Thanks for all the info and your thoughtful response. Not at all what I wanted to hear, but the facts are the facts. I’m going to look for a scale in my area tomorrow to confirm what you and others have warned me about. I'll never trust another trailer salesman. Unfortunately, I can’t afford a new truck, and really don’t want to part with my Tundra. And selling the trailer for a smaller one will take some doing (wife and kids). Until I can do one or the other I’m looking at the modifications you suggested.

The exhaust system is pretty easy but I don’t have the original pipe. Will a Gibson kit with single 2.5 inch pipe and the muffler you suggested work or should I try to buy a tail pipe from Toyota?

Consider the intake change back to stock a done deal. I’ll try to sell the K&N FIPK on ebay unless someone on the TS Forum is interested.

The headers are a possibility but I wonder about the CA emissions tests. Are the JBA headers emissions legal in CA. I couldn’t find a confirming statement on their web site.

Don’t know anything about gears but I’ll start learning.

As to towing what I have, I guess it’s short, smooth, flat, and safe as possible trips till I can come up with the right answer.

Thanks again, Glen

[RockyMtnRay]

Originally Posted by sawblade999

Ray, (and everyone else)

Thanks for all the info and your thoughtful response. Not at all what I wanted to hear, but the facts are the facts. I’m going to look for a scale in my area tomorrow to confirm what you and others have warned me about. I'll never trust another trailer salesman. Unfortunately, I can’t afford a new truck, and really don’t want to part with my Tundra. And selling the trailer for a smaller one will take some doing (wife and kids). Until I can do one or the other I’m looking at the modifications you suggested.

Welcome and I really hated to rain on your parade. But safe towing requires a sober, realistic assessment of your situation and neither trailer nor truck makers ever advertise anything close to realistic weights. So yes, definitely take your entire rig to a scale (loaded with all the gear, supplies, and people you would load for a trip) and be sure to get each axle weighed independently. I truly hope for your sake that my weight estimations are a little high and that you aren't as badly over the limits as I suspect you are. But I also well know that hardly anyone ever overestimates their rig's weight and as a result something like 60% of all rigs (especially 5th wheel and Motorhomes) exceed one or more of the manufacturers weight ratings.

The exhaust system is pretty easy but I don’t have the original pipe. Will a Gibson kit with single 2.5 inch pipe and the muffler you suggested work or should I try to buy a tail pipe from Toyota?

IMO, the Gibson Swept Side isn't quite as good as the muffler by itself for midrange torque (and possibly a bit more prone to have 2K drone) but a heckuva lot better than what you currently have, particularly when used with good headers (JBA or TRD). Member "KLS"...the other towing guru on this forum...installed the full Gibson catback in conjunction with S&S Longtube headers (sorry, those are not CARB certified) and has reported excellent performance results for towing. I think you'll be quite pleased with the performance and also happy with the sound...a soft rumble at idle, a little growl up to about 2200 RPM and then pretty much silent at high power when towing. Much, much easier on the family's ears when towing than your Flowmaster is.

Consider the intake change back to stock a done deal. I’ll try to sell the K&N FIPK on ebay unless someone on the TS Forum is interested.

Be sure to clean the MAF sensor after you go back to the stock intake. The oil that gets sucked off K&N filters is notorious for gunking up the heated wires in the MAF (mass air flow) and causing a serious loss of performance.

The headers are a possibility but I wonder about the CA emissions tests. Are the JBA headers emissions legal in CA. I couldn’t find a confirming statement on their web site.

There are only two CARB legal headers available for your year Tundra: JBA and TRD. Yes, JBA headers do have an official CARB emissions exemption so there will be no problem passing your smog tests. TRD headers were also CARB certified for '00-'02 Tundras. JBAs are more readily available (and less expensive) than TRDs and can be ordered with ceramic coating (TRD headers can't). The ceramic coating is a very effective insulator and dramatically cuts the amount of heat escaping into the engine compartment. Order them with the "titanium" rather than "silver" ceramic...the "titanium" colored ceramic is designed for "extreme" duty and your towing definitely qualifies as "extreme" duty.

Don’t know anything about gears but I’ll start learning.

As to towing what I have, I guess it’s short, smooth, flat, and safe as possible trips till I can come up with the right answer.

Thanks again, Glen

Welcome. Get your actual weights...and start tuning your truck for towing instead of racing. In addition to the regearing, headers, and exhaust mods previously discussed, you also have the option of adding a Unichip piggback ECU. The Unichip increases torque about another 10% and costs around $1000.

If you check my photo gallery, you'll see my trailer (when folded up for towing) is much lower profile and lower weight than yours (though at nearly 4000 lbs it's hardly a featherweight)...but I'm also towing at elevations from 4000 to 12,000 feet with accompanying power losses of 20 to 40 percent when compared to sea level. Even with the huge power loss due to altitude, my mods allow me to maintain the speed limit of 60 to 65 mph at an altitude of 10,000 feet on grades of as much as 5% without any downshifting out of 3rd gear! (OD off). On a recent trip with roughly 850 miles of almost continuous mountain towing, my transmission temperature never went over 185 degrees, mostly because I had so few downshifts to 2nd gear on steep grades. On flatter roads at lower elevations (like only 4000 feet ), the truck has enough available torque when towing that even passing cars & trucks on two-lane highways is safe & feasible! And even better, I'm averaging around 13.5 mpg while towing over these mountain roads...I suspect I could probably get over 14 mpg in flat, low elevation towing. I'm beginning to think "I'm there" when it comes to deciding if I have enough towing power.

[sprj8008]

It's a hard spot to find yourself in AFTER making the investment.

I'd also suggest a Helwig sway bar. My WIFE actually commented that the truck felt more stable this year with the trailer on, than last. It's an improvement and well worth the money.

The scales may teach you a bit on the trailer loading. I was working with Ray's 20% figure for my tongue weight but this was a bit lower than the scales showed. Be careful but more importantly be informed.

My trailer is licensed at 4000lbs. My axles weighed:
Front 1380 of 1433 licensed. (empty 1320)
Rear 1560 of 1796 licensed. (empty 1140)
Trailer 1810 of 1814

This includes all water, winter antifreeze in the grey/black tanks and the kitchen sink my wife decided was required for the trip. Heavy but within limits.

I'm seeing 420kg of tongue weight on 1810kg of trailer (23%).

The Supercharger may not be easy to find and is realistically harder on your engine and tranny but it's a blast empty and blows everyone away when you maintain speed on a 7% hill.

Jason

[Scottytundra]

I belive in CA you can get into some serious trouble if you cause an accident while towing overloaded.

I would never put my family in danger by towing a 7000lb trailer with my tundra.

POINT BLANK there is NO WAY you can tow that trailer safely with that truck.