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Discussion Starter #1
I recently went from a 31 inch diameter tire to a 34.5" diameter tire on a 4x4 4.6 liter Tundra. It seems like the truck shifts out of 6th gear alot more often now.. seems to hunt for the right gear alot more.

Has anybody noticed anything like this after a substantial tire diameter change? If so , what did you do to correct this problem? My apologies if this question has been addressed before.. I cant seem to find a thread for this specific problem.
 

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You have effectively changed your final drive ratio from 4.10 to 3.68. What did you expect???:eek:
 

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Discussion Starter #3
You have effectively changed your final drive ratio from 4.10 to 3.68. What did you expect???:eek:
Ya I get that. But this hunting happens while the truck is not under much stress at all. Just tooling along at 65 mph and I hit a very gradual incline and it starts hunting between 5 and 6 and like to stay in 5th afterward. I speed up a bit and it will go into 6th gear and stay there until the next small incline or headwind so i speed up or slow down by 2 or three mph and it will stay in 6th. This doesnt seem normal.

At times it will stay in 6th at 70mph for awhile and then it will refuse to go into 6th after an incline and back on flat ground unless I go a bit faster or a bit slower. Same deal at 65. I'm at the point right now that I am not using the cruise control at all because I can feather the throttle to keep it in 6th.

I gues what I'm looking for is a way to reprogram shift points.
 

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Hmmm, you can't really regear. Only option is really the calibrator.

I think seeing this post makes me NOT want the 34.5s anymore, even though it's kinda hard not to!

Your truck looks great btw, as I saw in the other thread you started.

-rockstate
 

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Discussion Starter #7
Thx for the info. I am going to give that calibrator a try. that and mabe upping the hp a bit with exhaust upgrades mabey a chip if one comes out for this engine.

Thx for the compliment on the truck appearance:D
 

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Maylon thx alot for that link.. the feedback alot of those guys describe are exactly what I'm dealing with and the calibrator seems to fix the problem.
I'm glad I could help!
 

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Discussion Starter #10
I was checking out the Tundra talk forums and I came across a thread where a guy has a 4.6 liter crewcab with a 7 inch BDS lift 20 inch wheels with 37 inch mudders and a 3 inch body lift.

OMG .. I wonder if that truck can get into 6th gear going downhill with a tailwind
 

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Hypertech speedo Calibrator was installed in my 5.7 and works like charm.
 

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signcutter- any luck with the hypertech? I noticed this problem on a road trip last weekend. I got worse fuel mileage using cruise at 75 mph on the highway then I do in city driving. my tires are only 33's and I thought it seemed quicker around town after the lift/tires - 75mph in 6th gear is 1900 rpm but every little hill it drops to 5 and on big hills down to 4th. if I take the cruise off I can keep it constant MPH within 2-3 mph no matter what grade the hill ....all staying in 6th gear. I think the computer is the culprit along with a sensitive cruise.

I'd like to hear some peoples experience with hypertech also.
 

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Discussion Starter #13
signcutter- any luck with the hypertech? I noticed this problem on a road trip last weekend. I got worse fuel mileage using cruise at 75 mph on the highway then I do in city driving. my tires are only 33's and I thought it seemed quicker around town after the lift/tires - 75mph in 6th gear is 1900 rpm but every little hill it drops to 5 and on big hills down to 4th. if I take the cruise off I can keep it constant MPH within 2-3 mph no matter what grade the hill ....all staying in 6th gear. I think the computer is the culprit along with a sensitive cruise.

I'd like to hear some peoples experience with hypertech also.
I havent gotten around to it yet.. wife kidnapped my truck for the last 7 days.. she just got back so I'm going to do this soon. Still have to do some odds and ends around the house.. so little time.. so much stuff to do.

You seem to be experiencing the exact same thing i am with the cruise control. I dont think engine power is the problem here at all. The engine can stay in 6th with no problem and maintain 70 mph on all the inclines I deal with the 70 mile distance between where I live and San Antonio.. as long as the cruise control is off.
I miss the days when all that determined speed and rpm was your foot and your brain
I love all that leg on your avatar.. where is that picture? It would make a great wallpaper

I'm thinking that the hypertech speedo thing will do the trickso the ecu wont be wondering why the hell the rpm and the speed dont match( speedo reads 64 mph at real speed of 70 mph).
As soon as I can get ths done I will post the results.
 

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The CC sucks on any vehicle. It's particular touchy on the Tundra. I always gain RPMs and speed before approaching a hill, even if it means breaking the speed limit by a few mph.

-rockstate
 

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Also, mike, what kind of mileage do you see at 75?

How bout in city?

I see about 15.5-16 with mine on the highway at 75-80 mph and like 12 in town, if I'm lucky.

-rockstate
 

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15-16 in town and I got just under 15 at 75mph using the cc for a whole tank. I was getting 18 in town before the lift and over 20 on the highway.
 

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Discussion Starter #17
15-16 in town and I got just under 15 at 75mph using the cc for a whole tank. I was getting 18 in town before the lift and over 20 on the highway.
Im not even going to try to get anywhere near what you get in mpg. With 4x4 and a slightly taller tire there is no way I'll match you. I get high 14's around town driving like I am Gras-hoppa and there is rice paper on my gas pedal. Its become habit so its not so bad. On the highway its rounded out to 16.5 mpg with a light foot. Lost like 2 mpg from the lift it seems
 

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Im not even going to try to get anywhere near what you get in mpg. With 4x4 and a slightly taller tire there is no way I'll match you. I get high 14's around town driving like I am Gras-hoppa and there is rice paper on my gas pedal. Its become habit so its not so bad. On the highway its rounded out to 16.5 mpg with a light foot. Lost like 2 mpg from the lift it seems

yea - I agree with losing about 2 mpg with the lift - that seems accurate to me. I'm happy with 15 for my daily driving - and I still romp on it often. seems like I always get 300 miles out of my tank and it always takes 20 gallons to fill up ... no matter what I do. I was just shocked the highway doeesn't get better - maybe its because I sit at 75. Overall it's better mileage than my old stock f150 with the 5.4. that was 14 for my daily driving. we'll see what the hypertech does - I think i'm going to go ahead and get it in a week or two.
 

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Old thread, just wondering what the outcome was? I have the same problem.

Thanks

Gary
 

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get a hypertech inline speed calibrator

this will let the truck know the actual speed and it will shift correctly. you can search Hypertech on this fourm and find good info
 
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