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Old 05-07-2005, 02:11 AM   #1
jamba
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Question I need an expert opinion!!

So here's my situation. I just put a 2" spring lift and a 2" body lift on my 03 baja (4eat). then I had to go with the bigger tires, so I went with 225/70-16s, which is about 6% bigger than stock. I'm not use to an auto tranny so I really underestimated how much the gearing would be affected. with a manual, there wouldn't be a problem... but it turns out I'm an idiot

for the past 2 days I've been trying out driving in 3rd grear during city driving (and putting it in "drive" when I get on the freeway). This seems to be helping to keep the rpm where it should be (between 2800 and 3200) rather than at 2200 at 40mph.

Here's my question: Is this bad for the tranny or anything else, how much am I damaging the car by doing this? Do you have any suggestions or recommendations?

PS- Try to resist the temptation to recommend smaller tires Captain Insight. It really, rreeaally looks good like this, and it's an extra inch of ground clearance for trail driving.

thanks
jack
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Old 05-07-2005, 02:35 AM   #2
Back Road Runner
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Well, it doesn't affect anything other than torque. Since it's an auto, I think it's just a matter of getting used to it again. You'll just run at a little lower rpm, that's all. Heck, your gas milage may improve if there isn't too much stop and go.

I'm curious why you don't like the car running at a lower rpm? I understand liking a little more "get up and go" by running it a little higher, but a little mash of the gas will kick it down anyways.

Get used to it, and enjoy your off-roader

I guess if it's such a hugh problem, you could always change the gearing...if there's something available for it. It could be good for off-roading and towing too.
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Old 05-07-2005, 03:42 AM   #3
2k4STi
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driving in 3rd shouldn't damage the tranny. I don't see why you just don't enjoy driving normal, it shouldn't be that much of a difference. I went from a 285 tire to a 315 tire, and the rpm problem didn't bug me unless i was really trying to get on the highway. You could regear... wouldn't be worth it IMO because you would have to replace the front and rear gears (pricey). If it really bugs you perhaps a programmer could help pinpoint when your automatic tranny shifts. Sorry if i'm just throwing out ideas, baja's are new to me.

kyle.
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Old 05-07-2005, 06:38 AM   #4
jamba
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thanks for the feedback, guys, keep it coming.

It's nice to hear that others wouldn't think it would make that much difference either, but it does. The only reason it bothers me is that it is running too low... like 2100 rpm at 45 mph ... I'm no expert but that can't be good. And it also seems to have problems deciding what gear to be in when I'm going below 50 in "drive"... it starts jerking just a little. It doesn't do that in 3rd though.

and actually I've lost about 3mpg... I think because I'm having to use at least the same amount or more of throttle pressure to maintain lower speeds.
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Old 05-07-2005, 11:38 AM   #5
2k4STi
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how is acceleration up hills? did you change rims and tires or just tires? If anyone offered a programmer for a baja that would be your best bet, what do you know about that?

When i have lifted cars in the past, a 3m.p.g. loss is not bad, but how different is your tire size. you have a 225 now, what was your old tire size?
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Old 05-08-2005, 01:10 AM   #6
jamba
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It does ok up hill, I put on headers, catback, and perfectpower chip. the oem size is 225/60-16, I put on 225/70-16 (same rims), it's about a 6% increase.

good idea with the programmer for the etu. I read that someone was trying to do that with the perfectpower chip, but I have no idea how that would work, and the folks that I've talked with said "well it could work, we would have to do some experimenting". unfortunately, their shop is about 800 miles away.

Do you know anyone I could talk to?
thanks
jack
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Old 05-08-2005, 01:49 AM   #7
2k4STi
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Did you drive around on the lift with your stock tires for a while, or change them immediatly when you got the lift. I really do not see how a 6% change would slow you down much if at all. Especially with the power mod you have... Hopefully someone else will chime in!!
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Old 05-09-2005, 12:04 AM   #8
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I understand it's "noticable" because you're used to how the car felt before you increased the tire size. However, you'll get used to it.

As well, I wouldn't worry about the shifting. It's set up for the othe size of tire, but nothing bad will come from the slight change. If it kicks up and down a lot, you're adding more wear and tear. A different driving style may fix it or aviod speeds that run in that magic shift spot. If reprogramming is possible, that may work very well for adjusting the tranny to the tire size.

A larger tire and lower mpg is expected as you have a little more rotating mass and a little less torque to work with for get up and go. Around the city, it would go down. On long highway trips, however, I'd think it might improve slightly with the lower rpm, if the throttle doesn't need to be depressed too much more where it would offset the gain from the lower rpm. Even the tire choice has a factor. Some tires have a higher rolling friction and decrease gas milage. I've heard this about the Traction T/A's, a few mpg lower just by tire.
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Old 05-09-2005, 12:34 AM   #9
Uncle Scotty
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...it isn't just the size difference, it is the weight and where the weight is that is affecting the performance....further from the center of the hub = more power to spin it up(and down, too)

...also, AFAIK, putting the trans in '3' just keeps it from upshifting into 4th, so no worries there.
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Old 05-13-2005, 03:00 AM   #10
jamba
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thanks Scotty, good to know.
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