Jtrux Posted June 11, 2016 Share Posted June 11, 2016 Does anyone have 3.55's and a 2.5L? I live in a relatively flat area and the 4.10's are pretty peppy so I'm thinking of sacrificing some pep and putting a taller gear in it. Before anyone goes on about price, I will be doing it myself. Gears themselves are not too bad. Link to comment Share on other sites More sharing options...
benjy_26 Posted June 11, 2016 Share Posted June 11, 2016 I have that set up with 31's and an AX4. It gets around fairly well, but I probably wouldn't get rid of 4.10's if I had em. Link to comment Share on other sites More sharing options...
pineymike Posted June 11, 2016 Share Posted June 11, 2016 My son ran 3:55's on his 4cyl for awhile with 33" tires it was alrite on the flat didn't take it to the hills. Link to comment Share on other sites More sharing options...
87Warrior Posted June 11, 2016 Share Posted June 11, 2016 Had them in my 86 with a 5speed. (wasn't the stock transmission) 5th gear was totally worthless. Keep in mind, I am in Kansas too. Link to comment Share on other sites More sharing options...
Jtrux Posted June 11, 2016 Author Share Posted June 11, 2016 Had them in my 86 with a 5speed. (wasn't the stock transmission) 5th gear was totally worthless. Keep in mind, I am in Kansas too. Tire size? I'm running 215/75-15's. Pretty small tires. Link to comment Share on other sites More sharing options...
87Warrior Posted June 11, 2016 Share Posted June 11, 2016 Tire size? I'm running 215/75-15's. Pretty small tires. 235/75r15 at the time. It's important to remember these old Jeep motors run like a Singer around 2300 RPM. Is there a reason why you wish to drop the cruising RPM with your 2.5? You don't mention 4 or 5 speed, but I assume you have a 5 speed. I can't foresee any benefit on a stock truck as I feel these trucks were under geared from the start. Link to comment Share on other sites More sharing options...
Jtrux Posted June 11, 2016 Author Share Posted June 11, 2016 I do not have a tach but according to my calculations I'm turning 3200 at 70 in 5th. Link to comment Share on other sites More sharing options...
Eagle Posted June 11, 2016 Share Posted June 11, 2016 Had them in my 86 with a 5speed. (wasn't the stock transmission) 5th gear was totally worthless. Keep in mind, I am in Kansas too. Tire size? I'm running 215/75-15's. Pretty small tires. There's a good reason the factory used 3.55 gears with the 4-speed and 4.10s with the 5-speed. I have an '88 2.5L 4-speed on stock tires, and there's no way I would describe it as "peppy." If I get energetic, I have intentions of converting it to a 5-speed and swapping the rear axle for one that's set up with 3.73 gears and a Traclok, but I regard it as an experiment. I fully expect that the 5th gear will be useless at anything slower than Interstate cruising speeds. In 5th gear on 215/75-15s, if you have stock 4.10 gears, 70 MPH should be 2700 RPM, not 3200. Link to comment Share on other sites More sharing options...
Jtrux Posted June 11, 2016 Author Share Posted June 11, 2016 I purchased mine for commuting to work and taking fishing. Work is 24 miles each way, all highway. Fishing is 150 miles or better each way, all highway. I usually catch fifth at about 55mph and it will climb up to 65 where I keep it. I'm wanting to be able to run 70/75 without revving it up too much. I just don't like it. It's very flat here so I'm not terribly worried but it could end up sucking. Link to comment Share on other sites More sharing options...
benjy_26 Posted June 12, 2016 Share Posted June 12, 2016 If you want to drop your rpm's in a way that's easily reversible, slap a pair of 235/75's on the back of your ride. It should reduce your cruising RPM. Link to comment Share on other sites More sharing options...
xjrev10 Posted June 12, 2016 Share Posted June 12, 2016 Yeah. That's what I was thinking. Go with a larger tire. Or at least try it first. You'll need a different carrier for your Dana 30 too if you go from 4:10 to 3:55. Link to comment Share on other sites More sharing options...
Jtrux Posted June 12, 2016 Author Share Posted June 12, 2016 These tires are brand new and I like the stance so they are here to stay. I have another carrier so no worries there. Still tossing it around. I'll drive it on some longer trips and see if the current set up grows on me. Link to comment Share on other sites More sharing options...
Eagle Posted June 12, 2016 Share Posted June 12, 2016 I purchased mine for commuting to work and taking fishing. Work is 24 miles each way, all highway. Fishing is 150 miles or better each way, all highway. I usually catch fifth at about 55mph and it will climb up to 65 where I keep it. I'm wanting to be able to run 70/75 without revving it up too much. I just don't like it. It's very flat here so I'm not terribly worried but it could end up sucking. 2700 RPM @ 70 MPH is not overrevving it. The 2.5L engine is a development based on the AMC 199/232/258 cubic inch I-6 that dates back to 1964. That was before most cars had overdrive, so top gear was almost always 1:1 ratio. The typical gearing and tire sizes used by AMC resulted in a ratio of 24 MPH per 1000 RPM -- and I owned several of them, so I know this from my own, personal experience. If you do the math from that, 60 MPH was exactly 2500 RPM, and 3000 RPM was 72 MPH. With gearing like that, my 1966 Rambler American got 28 MPG on the highway. The engines lasted forever. The one we know the most about was my brother's 1970 Gremlin. He ran it to about 250,000 miles, then he sold it to an auto parts store that used it for delivering parts. It was well over 300,000 miles before we lost track of it. Link to comment Share on other sites More sharing options...
gogmorgo Posted June 12, 2016 Share Posted June 12, 2016 If you were closer if swap you a 3.55-geared d30 for that 4.10... Link to comment Share on other sites More sharing options...
Pete M Posted June 12, 2016 Share Posted June 12, 2016 another vote for there's nothing wrong with those rpms. :thumbsup: the 2.5 is not the 4.0 and torque is at a premium (hence the 4.10 gears). heck, 2.5/autos came with 4.56 gears. :yes: Link to comment Share on other sites More sharing options...
outlaw star Posted June 13, 2016 Share Posted June 13, 2016 I have a stroked 2.5L (3.0L) with the AX-4, 4.10 D44 and 31" tires. My rpms at 65 are 3500-3600. Sent from my LGLS770 using Tapatalk Link to comment Share on other sites More sharing options...
gogmorgo Posted June 13, 2016 Share Posted June 13, 2016 Since we're now playing this game, my Lada's 1.7L four-cylinder turns 4500rpm at 60 mph. I regularly shift between 4,000 and 5,500 rpm, but passing on the highway (a rare occurrence) usually requires dropping to 3rd and running right to or beyond the 6,000 rpm redline (fuel cutoff is at 7k). Been driving like that for 10,000 miles and it hasn't exploded yet. I imagine the AMC 2.5L is better built... But my offer to swap D30's still stands, if anyone at all is interested. I have both CAD and Non-CAD w/3.55's. Link to comment Share on other sites More sharing options...
Eagle Posted June 13, 2016 Share Posted June 13, 2016 I have a stroked 2.5L (3.0L) with the AX-4, 4.10 D44 and 31" tires. My rpms at 65 are 3500-3600. Sent from my LGLS770 using Tapatalk 31" tires and 4.10 gears should only turn 3020 RPM at 65 MPH with an AX-4. Tell us more about this 2.5L stroker. I'd be very interested in a stroked 4-cylinder but, unlike the 4.0L, there aren't any other versions of the engine around that had different displacements and cranks with longer throws. How did you stroke it? Link to comment Share on other sites More sharing options...
outlaw star Posted June 13, 2016 Share Posted June 13, 2016 I have a stroked 2.5L (3.0L) with the AX-4, 4.10 D44 and 31" tires. My rpms at 65 are 3500-3600. Sent from my LGLS770 using Tapatalk 31" tires and 4.10 gears should only turn 3020 RPM at 65 MPH with an AX-4. Tell us more about this 2.5L stroker. I'd be very interested in a stroked 4-cylinder but, unlike the 4.0L, there aren't any other versions of the engine around that had different displacements and cranks with longer throws. How did you stroke it? Message sent. If you're using the grimmjeeper calculator, he openly admits that it will be plus or minus due to different variables such as tire manufactures advertised size are not exactly true, same goes for ring and pinions (some 4.10's are actually 4.11, etc..) Link to comment Share on other sites More sharing options...
FrankTheDog Posted June 13, 2016 Share Posted June 13, 2016 My 4.0 has been run constantly between 2500 and 3500 rpm. I put 4.10's in it at 240k and it is now at 437k. Street tires are 31's so figure 30" running diameter at best. I'm happy with the pep and fuel mileage. 17 mpg no matter how I drive. It sees redline a lot. Link to comment Share on other sites More sharing options...
Eagle Posted June 13, 2016 Share Posted June 13, 2016 Message sent. If you're using the grimmjeeper calculator, he openly admits that it will be plus or minus due to different variables such as tire manufactures advertised size are not exactly true, same goes for ring and pinions (some 4.10's are actually 4.11, etc..) I don't use anyone's calculator. I made my own spreadsheet, using actual revolutions-per-mile data from the tire manufacturers. With all (un)due modesty, I think it's the most accurate RPM to speed chart available. There's a sticky post somewhere here with a link to it on-line. Link to comment Share on other sites More sharing options...
Double Six Posted June 14, 2016 Share Posted June 14, 2016 I have this setup 2.5L 4-speed manual 3.55 rearend,not too peppy but does an ok job gets about 24 mpg. I have to do a lot of downshifting in the hills but thats ok I guess. when in 4L in 1st gear will go up anything. Link to comment Share on other sites More sharing options...
outlaw star Posted June 24, 2016 Share Posted June 24, 2016 Message sent. If you're using the grimmjeeper calculator, he openly admits that it will be plus or minus due to different variables such as tire manufactures advertised size are not exactly true, same goes for ring and pinions (some 4.10's are actually 4.11, etc..) I don't use anyone's calculator. I made my own spreadsheet, using actual revolutions-per-mile data from the tire manufacturers. With all (un)due modesty, I think it's the most accurate RPM to speed chart available. There's a sticky post somewhere here with a link to it on-line. I'd like to check that out actually, if you can find a link. Thanks. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted June 25, 2016 Share Posted June 25, 2016 https://docs.google.com/spreadsheets/d/1pHFuhGgj6dQDfzyfFJH5z7NCDLW2KX3ABQgAJr3lBvM/pub?hl=en&hl=en&output=html Link to comment Share on other sites More sharing options...
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