moos Posted February 14, 2016 Share Posted February 14, 2016 Alright let's get this started. My truck sittn it's a 1989 4.0l 4x4 manual with 3.07gears. With future plans of swappING newwe stuff. Anyways it was my dad's truck an been mine since I been driving 8 or 9 yrs now.here's my problem I decided to park her get another jeep as a dd then when i find the right doner. Well 3 yrs later I've accumulated 2 more mjs and let's not talk aboout the xjs (alot).anyways here's my dilemma one mj is a nice87 2wd,4.0l with a d44 nice spring overload setup with lsd 3.07 gears yes i checked,and she's clean no rust or dents. Others a turd 86 with 2.8l 4x4 with amc20 for mjs think m20 is the name and it has a 3in lift,anyways its beat up. Now I want to hear ideas,keep in mind I wants to downsize my collection having the 89 with best setup,87 with a decent setup for sale an 86 most likely somones truggy project for sale. Link to comment Share on other sites More sharing options...
Pete M Posted February 14, 2016 Share Posted February 14, 2016 what is it that you want in the end? Link to comment Share on other sites More sharing options...
moos Posted February 15, 2016 Author Share Posted February 15, 2016 I want the 89 to have atleast the lift an idk what axles to throw under it the d44 with limited slip an 3.07 gears,spring load helpers,is it enough gear wise with the lsd and 3in lift? Or the 20 and the front with most likely 4.10 gears . End game I want something I can DD and still tow a tiny trailer. I just don't wanna lift it an be struggling and i don't wanna get rid of somthing I'll need. tires wise ones I have laying around are bout 31s. I should atleast get rid of the 86 in the end. Link to comment Share on other sites More sharing options...
Pete M Posted February 15, 2016 Share Posted February 15, 2016 3.07s suck. 4.10s are awesome. :D Link to comment Share on other sites More sharing options...
moos Posted February 15, 2016 Author Share Posted February 15, 2016 I figured they did but hoped the lsd made up for it. Link to comment Share on other sites More sharing options...
Pete M Posted February 15, 2016 Share Posted February 15, 2016 you couldn't pay me to go back to a 3.07 gear. you could regear the 44, but is another ~600. you can buy a locker for the 20 for half that. Link to comment Share on other sites More sharing options...
moos Posted February 15, 2016 Author Share Posted February 15, 2016 Yea I'll just take the 89 throw the 4.10s under front n back. And put my 3.07 d35,an 30 on the 86 an sell it.looking at the 86s rear drive shaft looks alot thicker and the front looks whack are they interchangeable? Link to comment Share on other sites More sharing options...
Pete M Posted February 15, 2016 Share Posted February 15, 2016 there's a thread in the DIY forum covering all the various driveshaft lengths :thumbsup: Link to comment Share on other sites More sharing options...
Incommando Posted February 15, 2016 Share Posted February 15, 2016 I figured they did but hoped the lsd made up for it.The LSD shouldn't make a difference at all. Nor the lift height. The tire height that you chose is the deciding factor in altering the gear ratio that you have. Link to comment Share on other sites More sharing options...
moos Posted February 16, 2016 Author Share Posted February 16, 2016 I Think 31s. Link to comment Share on other sites More sharing options...
Jackrabbit41 Posted February 16, 2016 Share Posted February 16, 2016 I Think 31s. 31s with 4.10s is ok. I had it for a few weeks before i got my 33s. I wouldn't recommend it if its a DD. I like to go at least 65 but you might feel different. Link to comment Share on other sites More sharing options...
Eagle Posted February 16, 2016 Share Posted February 16, 2016 4.10s with 31" tires is perfect. 31" tires with 3.73 gears is exactly the same as 3.54 gears with stock tires, so 4.10s is only a small step more in gearing that stock when you run 31" tires. Check the ratio on that AMC 20. A lot of the 2.8L trucks and XJs had 3.73 gears. Link to comment Share on other sites More sharing options...
moos Posted February 16, 2016 Author Share Posted February 16, 2016 I decoded the vin while back and it said metric ton,but yeah I'll jack the rear spin a tire method n find out. Link to comment Share on other sites More sharing options...
Incommando Posted February 16, 2016 Share Posted February 16, 2016 The AMC was the metric ton axle that year. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 16, 2016 Share Posted February 16, 2016 4.10s with 31" tires is perfect. 31" tires with 3.73 gears is exactly the same as 3.54 gears with stock tires, so 4.10s is only a small step more in gearing that stock when you run 31" tires. Check the ratio on that AMC 20. A lot of the 2.8L trucks and XJs had 3.73 gears. According to the parts manual, the only AMC 20 axle available in the 86 MJ's were 4.10 ratio w. or w/o limited slip. Only the XJs had 3.73 and other ratios. Check that out Eagle if you get a chance - I may be reading this all wrong............ Link to comment Share on other sites More sharing options...
outlaw star Posted February 16, 2016 Share Posted February 16, 2016 4.10s with 31" tires is perfect. 31" tires with 3.73 gears is exactly the same as 3.54 gears with stock tires, so 4.10s is only a small step more in gearing that stock when you run 31" tires. Check the ratio on that AMC 20. A lot of the 2.8L trucks and XJs had 3.73 gears. Correct. I'm running 31" tires (30.8" true measurement) with a 4.10 ratio. So my effective ratio is close to 3.73:1 28/30.8 x 4.10 = 3.72:1 Link to comment Share on other sites More sharing options...
buckwheat Posted February 17, 2016 Share Posted February 17, 2016 I will side with Jackrabbit on this one. I have 31" tires and 4.10 gearing and its too deep for my liking. Tach reads 2300 or so at 65mph. Its a small difference, but i think 4.10s paired with narrow 33" tires would be the perfect combo. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 17, 2016 Share Posted February 17, 2016 I will side with Jackrabbit on this one. I have 31" tires and 4.10 gearing and its too deep for my liking. Tach reads 2300 or so at 65mph. Its a small difference, but i think 4.10s paired with narrow 33" tires would be the perfect combo. Do you have the correct speedo gear installed? Your tach should be reading ~2100 RPM with that combination. Link to comment Share on other sites More sharing options...
buckwheat Posted February 17, 2016 Share Posted February 17, 2016 Yup. speedo gear is correct and speedometer is verified with gps over several intervals. Link to comment Share on other sites More sharing options...
Pete M Posted February 17, 2016 Share Posted February 17, 2016 a bone stock 2.5L/5speed comes with 4.10s and waaaay smaller than 31" tires. My dakota R/T came with a big v8 and 3.92 and 28" tires. heck, the 2.5L/auto Jeeps came with 4.56 gears and tiny tires. there is nothing wrong with 4.10s and 31s. nothing at all. Link to comment Share on other sites More sharing options...
moos Posted February 17, 2016 Author Share Posted February 17, 2016 Haven't done the swap yet went to move the 2wd an no brakes ..well kinda I had pump an pump bout 3 times to get a bite. So ima try clean it today. Also anyone know if the rear drive shaft is direct swap from the 86 to 89,also how do I post pics from a galaxy s5 phone Link to comment Share on other sites More sharing options...
Pete M Posted February 17, 2016 Share Posted February 17, 2016 driveshaft lengths are in the driveshaft thread. chances are slim that the yokes will directly swap between a 4.0 and a 2.5/2.8 truck. I believe those spline counts are different. http://comancheclub.com/topic/48710-diy-projects-writeups-master-search-index/ Link to comment Share on other sites More sharing options...
moos Posted February 18, 2016 Author Share Posted February 18, 2016 Dam the splines won't work? I noticed a 1in difference in length. Any way to change it hahaha ah...life. Idk went to work on it and radio stuck on my vw so more sheeet to fix. Link to comment Share on other sites More sharing options...
FrankTheDog Posted February 18, 2016 Share Posted February 18, 2016 I've been running 4.10's and 31-32's for 200k on my 98 XJ. I have no problem running it 80mph on the interstate for hours. It has 433k on the original motor. I've been spinning that motor good for a long time and there are no issues with the engine. Get's 17-18 mpg too. Link to comment Share on other sites More sharing options...
Eagle Posted February 18, 2016 Share Posted February 18, 2016 I will side with Jackrabbit on this one. I have 31" tires and 4.10 gearing and its too deep for my liking. Tach reads 2300 or so at 65mph. Its a small difference, but i think 4.10s paired with narrow 33" tires would be the perfect combo. Do you have the correct speedo gear installed? Your tach should be reading ~2100 RPM with that combination. No, 2265 RPM at 65 MPH is correct. The question is why that's a concern. That's right about on the torque peak of the engine, which is the most efficient cruise speed for the engine, and it's slower than what the original AMC engines were designed for. As I've posted before, over the years, starting in 1966, my family has had a number of cars with the AMC 199, 232, 258 engine, all set up with non-overdrive 3-speed transmissions. They were all geared to run 24 MPH per 1,000 RPM -- which works out to 2500 RPM at 60 MPH, and a 72 MPH cruise at 3,000 RPM. Set up like that, we've seen them go more than 300,000 miles. 2,300 RPM at 65 MPH is not an issue. Link to comment Share on other sites More sharing options...
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