On my old truck, over the last 6 months the power train seemed to have a bad decline on power, mostly in the transmission area to be exact. Recap, it was a 2004 5.4L with the 4r75e? And was custom tuned 87 oct with dual 2.5" true duals, 3.73 LSD axle code B6. Anywho the truck ran 20"x9" XDs wrapped with 33x12.5/20 Toyo M/Ts for 1.5yrs & 30,000 or so miles. Granted the truck was a partial towing truck by original owner and I had 'hot-dogged' a little with it as seen in some videos, the transmission gave me troubles on the last 6 months to year of ownership. There had been a full second+ delay when engaging reverse, and a minor slip at times. I have over read on some posts the 04/05 transmissions aren't as strong as the '06+ are, any truth to this?

I am afraid to do similar modifications to my new '07 5.4L 3.73 axle 26 ( 3.73 open ) due to all of the mishap with my '04. I kind of believe the weight of the 33s and the true dual exhaust lead to some strain to the power train when worked hard. As it is all stock it feels much more solid and performing than my '04 did. I daily drive my truck and want to get a 3" exhaust and put the XDs on this truck but I don't want to hurt the power train of this one. Should I re-gear? I really don't foresee myself ever suspension lifting but I could see the truck running 33s or 34s for the rest of its life so I do not know if a re-gear would be worth investing in. Something like 4.10s? What is most necessary to turn 33s - 35s non lifted? I also want to get my 'fairly good economy' that I did with the 3.73s & 33s.

Hopefully my troubles with the old truck were due to the suppository 'wearer' transmission and the work I had forced it to do for fun. I have really no intentions on abusing my newer truck but still want to get tuned and roll XD 20s again leveled. Do I have much to worry about? How would the 3.73 open rear move the 33s? I do want to get a LSD if I change out the rear axle fluid so it most likely won't be an open setup for ever.

Any more comments/advisory welcomed.

 

a 33 is only about 1" bigger than my stock FX4 tires (LT275/65-18), I wouldnt worry about 33's on 20" wheels. if u went with 35's or bigger then that would be strain on the tranny in my opinion

 

my stand on the trans and tires thing is that if you put a tuner on it and correct the tire size (so the pcm knows what the tires are spinning) then your okay.

if you want your trans to last a while get 33's, leave the 3.73's, and get a tuner to correct for the tire size, and make it shift harder (im running a gryphon) and then drop the trans pan and change the filter and put 5 new quarts of fluid in every 30k. thats what im doing and my trans is in great shape.

another thing to do would be to compare the tires you are interested in and pick the lightest of the bunch. if you get a tire thats 4 pounds lighter per tire, then your saving all that power and strain. might not be noticable to you and your right foot power wise, but it will be less strain on the truck. 16 pounds over as long as the tires last is a difference.

and if you wanted to get even more picky get a mag hytec trans pan. or that and that factory tech separator plate to make it shift even more firm. then if you wanted to you can also add an in line filter to the trans return line. or even add a oem trans pan (or mag hitec) with the drain bolt in it. then you can add 5 new quarts of merc 5 every 15k or so, and do the gasket every 30. more maintanance? yes, better for the trans? has to be.

 

barely taller than stock, but they weigh a ton more. Especially those Toyo MTs, they are heavier than just about anything other model tire in each comparable size. Plus they are wider than stock which means more surface area hitting the ground, meaning more friction and more power needed.

Darren I think you just had a lemon. My first tranny had the same symptoms yours did (stock tune its whole life) and it died at 72k miles. My 2nd tranny is a Ford rebuild and has spent 50k miles with a Troyer tune, and ~35k of those miles on heavy 35s with stock gears. It still shifts firmer and reacts faster than my original tranny ever did with stock tires. Its a crap shoot IMO - some of these trannys are bullit proof, some are lemons. The only time it struggles is uphill because of the tires, but I'm finally regearing to 4.56 in a couple weeks. If you want 33s, by all means do it. Maybe do a 285/x/x in a 33 (less wide) and something besides those Toyo hulks.

 

I've never been a fan of tuners that increase line pressure. The extra pressure in my mind can only add more stress, kind of like a person with high blood pressure. I opt'd to go the mechanical route and installed a valve body on my truck, though this is not for everyone as the shifts depending upon your trans spring setup can be somewhat violent. However with the valve body the trans works fine at stock level pressures but shifts like an animal.

So far so good on my 05 and I have been pushing 37's and loads of torque for a few years now.

 

On my 2007 I ran 285/70/17's for 20K miles with 3.73 gearing and the truck pulled it fine no problems, just exhaust done. I than stepped up to 315/70/17 with 3.73 gearing with custom tunes, under drive pulleys, exhaust, intake, efans, mag hytech deep dish trans pan, troyer trans cooler and had a valve body. Truck 0-20ish was a slight dog, yet once I got going no problems what so ever. Now I have 265/70/17 with all the mods above minus the valve body and I absolutely love it! You will be fine with what you want to run, it will add some stress, yet from the sounds of it you will be fine. Just make sure tire pressure is up (made a big difference with the 315's on my truck) and rotate the tires every oil change. No need to worry about transmission failure or anything else with the truck for that matter. As it seems like you do little to no towing and "sometimes" have a heavy foot. I towed 6k lbs when I had 315's and did well. Also no need to do 4:10's from 3:73 difference will be so small you will say why did I waste the money. If anything go with 4:56's and you will do 0-80, will also take you for a ride! Fuel mileage will drop 1-2MPG with the heavier tires, yet the tuner will help the trans not hunt around and correct the PCM from messing anything up. On the LSD go with a true track diff, a much better product than the factory LSD in my book.

 

I am running 33's on 20's and do a lot of towing some of it very heavy on my 2005, 3.73 LS with 75000 miles. I do have the tow package and a tuner. I had a fluid echange done on the tranny at about 65000. I have had zero issues with transmission so far.

It's a truck so adding some rolling weight and slightly taller tires to a daily driver shouldn't kill the tranny. I mean they are designed to be able to tow and haul so I don't see it as a ton of stress that would require a rebuild and regear. 38's and a big lift is a different story.

If your truck doesn't have a tranny cooler you might want to add one. Other than that I wouldn't worry about it!

 

Im running a 315/70/17 on a 4.2 with 3.55 open diff. Seems to be running fine to me. You'll be good to go.

 

Hey guys instead of opening a new thread, will 285 70 17 fit on stock wheels on a 05 f150 xlt 2wd with a 2inch rear drop shackle?

 

My last truck was an 06 screw...leveled true dual maggies with 20"xd's with 33' tires. traded the truck with 75k miles and never had a problem. I used this truck for all sorts of things and never had a problem with the power train other then it was a dog with the 3:55's and no tune

 

Your gonna have to lift it to fit 285's. Level kit in the front and back to stock in the rear.

 

id like to read more into the line pressure ordeal with edge/gryphon tuners. wheres that guy with the 8 foot bed truck thats done a mag hitec and filter and factory tech separator plate

 

There are lots of people that run tires quite a bit larger than 33's with factory gearing and the stock tranny is fine. I wouldn't worry too much. IMO, if a truck can't handle something mild like a 33" tire, then you should look at another truck.

 

I agree with Big Slick, I run 275/70R18 (33in) on stock wheels onroad, offroad, towing/hauling... with no problems so far. I had 35's on an older ford and ran for years with no problems.

If you are worried about it then dont do it but 33in is only 1in over the standard OEM 4x4 tires. And yes a bigger tire is always heavier so if you want piece of mind take fivespeedsteed's advice and get a tuner and correct the tire size.

 

I have a 2" level with 305/65R18 BFG AT. They are a 33.7 inches, and 12.2 inches wide. I have been running them a while now and haven't notice a difference since initially puttin them on. 3.73 setup. I do have custom 87 and 93 tunes for my Edge/Gryphon.