idahoeagle Posted July 4, 2010 Share Posted July 4, 2010 Has anyone swapped in a 23.5 gallon tank from a longbed into a shortbed? My tank started leaking bad and I have an 87 4.o shortbed MJ and I'd like to swap in the 23.5 gallon from the long bed but it's my DD and I can't afford the downtime or expense to experiment to see if it can be done or what's needed to complete the swap... Can anyone help with pics/info? Link to comment Share on other sites More sharing options...
Pete M Posted July 4, 2010 Share Posted July 4, 2010 I seem to remember someone said the bigger tank would contact the rear axle. Link to comment Share on other sites More sharing options...
idahoeagle Posted July 4, 2010 Author Share Posted July 4, 2010 They are longer towards the front by about 7"... And the fuel filler is slightly closer to the rear of the tank... Link to comment Share on other sites More sharing options...
Pete M Posted July 4, 2010 Share Posted July 4, 2010 whoops, that should have read "would contact", not "wouldn't contact". crawling around in the dark, I get about 9" from tank to axle in my shortbed. Not exactly much of a comfort margin. plus with all the differences here and there (hangers, fill spout), I think you'll be better off with a new tank. To the best of my knowledge, no one has yet installed a 23.5 in a shortbed. Link to comment Share on other sites More sharing options...
idahoeagle Posted July 6, 2010 Author Share Posted July 6, 2010 From filler to the rear of the tank the 23.5 gallon there is less tank than the 18 gallon has... But it is 7" longer overall than the 18 gallon is... Link to comment Share on other sites More sharing options...
johnj92131 Posted July 6, 2010 Share Posted July 6, 2010 From filler to the rear of the tank the 23.5 gallon there is less tank than the 18 gallon has... But it is 7" longer overall than the 18 gallon is... So how close to the rear axel is each tank. I read the above as saying the 18 gallon tank rear end is closer to the rear axel than the 23.5 gal. tank. So the extra capacity of the 23 gal tank is all closer to the front of the truck? Do I have that right? Link to comment Share on other sites More sharing options...
Wildman Posted July 6, 2010 Share Posted July 6, 2010 You have it right if you use - An 18 gallon gas tank in the SWB ONLY!!! Or an 18 gallon OR 23.5 gallon gas tank in the LWB. Beside the different locations of the filler neck, the Larger tank will hit the rear axle on a SWB. If you want to carry extra fuel........Buy some Gerry Cans :yes: Link to comment Share on other sites More sharing options...
idahoeagle Posted July 9, 2010 Author Share Posted July 9, 2010 How can it hit the rear axle if the extra length is in the front end of the tank? The filler neck on the 23.5 gallon tank is closer to the rear than the 18 gallon... And the filler on the bed cannot move, so how could it possibly hit the rear axle??? Link to comment Share on other sites More sharing options...
Pete M Posted July 9, 2010 Share Posted July 9, 2010 there's no extra room in front of the shortbed tank. if the 23.5 is several inches longer in front of the fill, then the fill won't line up in the shortbed and that will push everything back towards the rear axle.. Link to comment Share on other sites More sharing options...
Wildman Posted July 9, 2010 Share Posted July 9, 2010 How can it hit the rear axle if the extra length is in the front end of the tank? The filler neck on the 23.5 gallon tank is closer to the rear than the 18 gallon... And the filler on the bed cannot move, so how could it possibly hit the rear axle??? The LWB tank (23.5 gallon) is longer towards the rear. Check the filler door location on a SWB and a LWB......the filler door is toward the rear, near the wheel flair, where on the SWB, the filler door is about mid point of that quarter panel. Thus......the filler neck is toward the rear, and the extra 5.5 gallons is toward the rear. The front 2 straps are in the same location for both the 18 gallon tank, and the 23.5 gallon tank, the 3rd strap is for the "longer" tank. So, if the SWB tank is say.......5" from the rear axle, and the LWB tank is say 7" longer.....were does it end up :hmm: I'll get time Saturday to measure both tanks and let you know the lengths, the above measurements I'm just pulling out of my head. Link to comment Share on other sites More sharing options...
jimoshel Posted July 9, 2010 Share Posted July 9, 2010 Quite frankly I think it can be done. Take a BFH and beat in both ends of the tank a couple inches. Move the filler hole back a foot, or mickey mouse a 's' tube to connect the tank and filler door. Also quite frankly I don't think it would be worth the trouble. There are better ways. I think one way would be to route the exhaust pipe outside the frame rail and install a MJ 18 gal tank in the space between the frame and drive shaft. A mirror image of the original, only reversed. Or get a universal replacement type that will fit in the space. Connect the two tanks with a cross over feed or separate them completely, using a separate filler and feeding them into a switchable 'Y'. short box filler door location long box filler door loc short box with 18 gallon tank that's how much room you got to play with 23 gallon tank on top Link to comment Share on other sites More sharing options...
idahoeagle Posted July 9, 2010 Author Share Posted July 9, 2010 Thank you jimoshel... Those pictures helped quite a bit. My point about the fuel filler location on the tank is that if you left the filler neck/filler tube location alone, is that the tank is longer in front of the filler, and shorter behind. I totally didn't think to look at cab support clearance at the front of the tank... I guess that means I'm stuck with just buying a replacement tank and calling it good... What do you know about using an XJ fuel sender in an MJ tank? I can't find a new replacement for the MJ and I'd like to make the guage operational again but don't want to put used junk in a new tank if avoidable... Link to comment Share on other sites More sharing options...
Jeepman Posted July 10, 2010 Share Posted July 10, 2010 Xj Fuel senders are Wrong for the MJ tank because they are too short and turn the wrong way however if your not afraid to modify the XJ sender you can turn it into a proper MJ sender as I did 2 years ago for my HO conversion on my 89 MJ... I bought a Brand new XJ sender that matched my Swap year (if you do not match your year the gauge will read backwards) then I cut it and lengthed the tubing insde and rotated the filter to the proper size so it is easy to do just takes a little time and you will have a brand new MJ sender made from a XJ sender... Good luck Link to comment Share on other sites More sharing options...
Wildman Posted July 11, 2010 Share Posted July 11, 2010 jimoshel - Thanks for loading up the pictures :bowdown: Now......I'll add the measurements - SWB = 18 gallon tank - appox 30" long, filler neck, 18" from rear of tank. * 8" from rear axle * LWB = 23.5 gallon tank - appox 36" long, filler neck, 10" from rear of tank. As I stated above, I'll still stand on what I wrote. Link to comment Share on other sites More sharing options...
Julio_Az Posted November 26, 2014 Share Posted November 26, 2014 Can the straps from a 23.5 gallon tank be used on 18??? Link to comment Share on other sites More sharing options...
mvusse Posted November 26, 2014 Share Posted November 26, 2014 I do believe the straps are the same. The short bed tank uses 2, the long bed one uses 3 of them. Link to comment Share on other sites More sharing options...
Swampy Posted October 9, 2017 Share Posted October 9, 2017 Sorry for bringing up an old thread but I didn't want to start a new one. Did anyone else see the jcroffroad Comanche and how they put a tj tank in the rear between the frame rails? I thought it was a cool idea and raise the ground clearance under the truck a few inches. My question is about the filler neck, the fuel sender unit, fuel pump and fuel lines? what would have to change to make it work? Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 9, 2017 Share Posted October 9, 2017 28 minutes ago, Swampy said: Sorry for bringing up an old thread but I didn't want to start a new one. Did anyone else see the jcroffroad Comanche and how they put a tj tank in the rear between the frame rails? I thought it was a cool idea and raise the ground clearance under the truck a few inches. My question is about the filler neck, the fuel sender unit, fuel pump and fuel lines? what would have to change to make it work? I'm not familiar enough with their build to know. Did they do a 97+ swap at the same time? Because if so, the 97+ fuel system, cluster, and fuel pump wiring would likely play nice with the TJ tank. Otherwise it should be a matter of adding a return line to the tank, and swapping the sending unit guts (and perhaps the fuel pump) over to the TJ pump/sender/pickup basket. You would have to bend/trim the arm on the sender correctly for it to read accurately. I think the TJ pump basket also has a regulator on it, you could likely leave it in place though. I've toyed with adding a YJ tank as an aux tank, I was just going to graft a XJ fill neck and sheetmetal into the rear of the bedside, it looked like it was possible to snake a filler hose through the frame back there, BUT you might need to cut/weld a notch in for it. This really should be a new thread, it's a different topic really... Link to comment Share on other sites More sharing options...
Dzimm Posted October 9, 2017 Share Posted October 9, 2017 Holy dead thread.. I'll play along.. A mid to late 90s 22gallon tank from a Dodge Dakota fits in the factory location under the swb nicely. With the 97+ swap you can buy a Mopar adapter to hook the Dakota fuel pump up to the XJ fuel pump wiring and everything works perfectly. This also keeps the tank up under the truck more to avoid untimely penetration that a rear mounted tank can easily suffer. Link to comment Share on other sites More sharing options...
Swampy Posted October 11, 2017 Share Posted October 11, 2017 On 10/9/2017 at 11:53 AM, DirtyComanche said: I'm not familiar enough with their build to know. Did they do a 97+ swap at the same time? Because if so, the 97+ fuel system, cluster, and fuel pump wiring would likely play nice with the TJ tank. Otherwise it should be a matter of adding a return line to the tank, and swapping the sending unit guts (and perhaps the fuel pump) over to the TJ pump/sender/pickup basket. You would have to bend/trim the arm on the sender correctly for it to read accurately. I think the TJ pump basket also has a regulator on it, you could likely leave it in place though. I've toyed with adding a YJ tank as an aux tank, I was just going to graft a XJ fill neck and sheetmetal into the rear of the bedside, it looked like it was possible to snake a filler hose through the frame back there, BUT you might need to cut/weld a notch in for it. This really should be a new thread, it's a different topic really... I am pretty sure their mj was bought already with the 97+ swap done. Should I really start a new thread? On 10/9/2017 at 12:08 PM, Dzimm said: Holy dead thread.. I'll play along.. A mid to late 90s 22gallon tank from a Dodge Dakota fits in the factory location under the swb nicely. With the 97+ swap you can buy a Mopar adapter to hook the Dakota fuel pump up to the XJ fuel pump wiring and everything works perfectly. This also keeps the tank up under the truck more to avoid untimely penetration that a rear mounted tank can easily suffer. So a stock fuel tank would be better than a rear mounted one? Link to comment Share on other sites More sharing options...
Dzimm Posted October 11, 2017 Share Posted October 11, 2017 4 minutes ago, Swampy said: I am pretty sure their mj was bought already with the 97+ swap done. Should I really start a new thread? So a stock fuel tank would be better than a rear mounted one? The stock Dakota tank would keep it tucked up between the frame rails and in front of the rear axle but it does hang slightly low so a skid plate would be recommended. The tank mounted behind the rear axle (TJ tank) would hang out and be more likely to be hit offroading when coming down off obstacles and if you were rear-ended, could explode like the XJs do. The best use for the TJ tank IMO is if you want an second fuel tank to get added fuel range. Link to comment Share on other sites More sharing options...
Swampy Posted October 11, 2017 Share Posted October 11, 2017 1 minute ago, Dzimm said: The stock Dakota tank would keep it tucked up between the frame rails and in front of the rear axle but it does hang slightly low so a skid plate would be recommended. The tank mounted behind the rear axle (TJ tank) would hang out and be more likely to be hit offroading when coming down off obstacles and if you were rear-ended, could explode like the XJs do. The best use for the TJ tank IMO is if you want an second fuel tank to get added fuel range. Thanks for the info bud Link to comment Share on other sites More sharing options...
Dzimm Posted October 11, 2017 Share Posted October 11, 2017 1 minute ago, Swampy said: Thanks for the info bud Anytime. I've done tons of research on the Dakota swap so any questions, just ask. Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 11, 2017 Share Posted October 11, 2017 3 hours ago, Swampy said: I am pretty sure their mj was bought already with the 97+ swap done. Should I really start a new thread? No point now. Does anyone have a picture of the TJ tank installed in a MJ? Link to comment Share on other sites More sharing options...
Goose_XJ88 Posted March 17, 2019 Share Posted March 17, 2019 Alright, digging this thread up again because I found what I believe to be a 23 gallon tank in my swb. I'm not 100% but here are the things I know. Tank is metal It is 32"-33" long It hits the d35 on the corner because of the housing It is only held in with 2 straps I have put in 21 gallons once with the normal click off (not 10 topping off clicks) The filler and vent tubes are pretty skewed and can be seen in the rear fenderwell What are your thoughts? Link to comment Share on other sites More sharing options...
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