350TacoZilla
Member
- 263
- 0
- 16
- Location
- Hancock MD
Hey guys let me start by saying this is a bench racing/ future build type of thread that I have been thinking about. I wanted to get bit of info on the axles listed and what differences to look out for, I have seen ton of contradicting info on net and wanted to try and get some clear info from you guys that have experience with them.
Project these are going into would be a 5 ton civilian truck converted to 4x4 with the stock engine similar in power/speed to the 855 cummins, looking to run between 11.00R20 duals-335/80R20-365/80R20 or might have to jump up to the more common 395/85R20 and would like truck to be able to run 65 on interstate without redlining it so in theory geared for top speed of 75. I would love to be able to say truck with have an OD trans but their harder to find so I'm going to base this on the idea its 1:1 top gear. Trying to keep overall height of truck down from monster sized so it doesnt stick out running down rd with trailer behind it.
Right away I am not a fan of the MRAP bolt pattern since it is basically its own size and nothing else fits, I like the idea of keeping the old budd style 10 bolt pattern like the 5T and fmtv stuff. I have seen posts saying stock fmtv gearing is 3.90 R&P with a 2:1 gear reduction but they are not planetary axles, also that you can swap in 3.07 R&P into these axles. Boyce lists the MRAPs at 6.857 gearing that they have but I have seen others say 5.65 is fairly common, also the MRAP transfer case is 1:1 high range divorce mount where the FMTV is married style so its pretty much nix'd.
If I run an M939 transfer case with its .732 high range then the gearing options are bit better but not great and I imagine I can get an adapter made for either style axle to run 5T driveshafts. Rockwell 5T axles would give me option of either 6.44 or 5.81 gearing which isnt bad but I dont like the height the top loader brings in.
So is there anything I'm missing here? everyone seems to be all about the MRAP axles but I dont ever hear much about the lmtv-fmtv stuff, is there a reason for this? I'm not made of money and probably never will be so scrounging this stuff 2nd hand is my only chance to get it probably. Would you just go with tried and true 5T stuff and forget about the newer faceloads?
If I go with 5T stuff it is right in zone I could live with but again top loaders mean tall truck.
1:1 trans x .732 T-case x 5.81 R&P x 43" tire (right in middle of options)= 2100rpm @ 63mph
even better overall build- 1:1 trans x .732 T-case x 5.65 R&P x 41" tire = 2100rpm @ 62mph
Obviously if I could luck into a OD medium duty trans it would make even the 6.44-6.857 gears more usable and I'm not against that option just hard to locate one.
Project these are going into would be a 5 ton civilian truck converted to 4x4 with the stock engine similar in power/speed to the 855 cummins, looking to run between 11.00R20 duals-335/80R20-365/80R20 or might have to jump up to the more common 395/85R20 and would like truck to be able to run 65 on interstate without redlining it so in theory geared for top speed of 75. I would love to be able to say truck with have an OD trans but their harder to find so I'm going to base this on the idea its 1:1 top gear. Trying to keep overall height of truck down from monster sized so it doesnt stick out running down rd with trailer behind it.
Right away I am not a fan of the MRAP bolt pattern since it is basically its own size and nothing else fits, I like the idea of keeping the old budd style 10 bolt pattern like the 5T and fmtv stuff. I have seen posts saying stock fmtv gearing is 3.90 R&P with a 2:1 gear reduction but they are not planetary axles, also that you can swap in 3.07 R&P into these axles. Boyce lists the MRAPs at 6.857 gearing that they have but I have seen others say 5.65 is fairly common, also the MRAP transfer case is 1:1 high range divorce mount where the FMTV is married style so its pretty much nix'd.
If I run an M939 transfer case with its .732 high range then the gearing options are bit better but not great and I imagine I can get an adapter made for either style axle to run 5T driveshafts. Rockwell 5T axles would give me option of either 6.44 or 5.81 gearing which isnt bad but I dont like the height the top loader brings in.
So is there anything I'm missing here? everyone seems to be all about the MRAP axles but I dont ever hear much about the lmtv-fmtv stuff, is there a reason for this? I'm not made of money and probably never will be so scrounging this stuff 2nd hand is my only chance to get it probably. Would you just go with tried and true 5T stuff and forget about the newer faceloads?
If I go with 5T stuff it is right in zone I could live with but again top loaders mean tall truck.
1:1 trans x .732 T-case x 5.81 R&P x 43" tire (right in middle of options)= 2100rpm @ 63mph
even better overall build- 1:1 trans x .732 T-case x 5.65 R&P x 41" tire = 2100rpm @ 62mph
Obviously if I could luck into a OD medium duty trans it would make even the 6.44-6.857 gears more usable and I'm not against that option just hard to locate one.