Variations of Transmission and Transfer cases for swaps - what is the best?

[coldwater]

Hi everyone. Thanks for all of the info. I'm TDY in Germany right now, so I haven't had a lot of time to reply to any of the postings. What I'm actually looking to do is replace the 3 speed T-150 with something that would allow me to reach highway cruise speeds without burning 10MPG in fuel. Right now the two Jeeps that I have both have the T-150 trans, the 1975 CJ-5 has a 304 V8 and the 1979 CJ-5 has the 4.2L 258 I6. Just to recap, I'm basically trying to find the best/easiest way to make driving at higher speeds a reality while maintaining the ability to use it off road. Thanks!

MUCH GOOD INFORMATION WAS GIVEN OVER THE COURSE OF THIS THREAD, HOWEVER, IT TURNED UGLY FOR NO GOOD REASON. HOPEFULLY EVERYONE HAS CALMED DOWN ENOUGH TO ADDRESS HIS NEEDS, AND WE CAN HELP HIM OUT. AFTER ALLL, THAT IS WHY WE EXIST AS A SITE.


Hi Orion, thanks for coming back! The problem with an easy, cheap (ish) swap for your jeep is that in the end, a 4 speed will still offer you a 1-1 ratio in top gear. I am not versed in the 5 speed trannies, as they were post CJ, and not of interest to me, but I don't think they were of good quality, and can't comment on the ease of a swap into your Jeep. You may be a bit Limited because of your driveline length as to all of the options out there. I'm sure one of the guys here can offer a fairly stock option that can help you out.

 

[LongHorn]

Hi everyone. Thanks for all of the info. I'm TDY in Germany right now, so I haven't had a lot of time to reply to any of the postings. What I'm actually looking to do is replace the 3 speed T-150 with something that would allow me to reach highway cruise speeds without burning 10MPG in fuel. Right now the two Jeeps that I have both have the T-150 trans, the 1975 CJ-5 has a 304 V8 and the 1979 CJ-5 has the 4.2L 258 I6. Just to recap, I'm basically trying to find the best/easiest way to make driving at higher speeds a reality while maintaining the ability to use it off road. Thanks!

I hope your not talking German highway speeds. I did some TDY in Bad Tolz. But seriously, some more specifics would help. Like final drive ratio your running, Tire size, are your engines stock? A CJ is not know for their aerodynamic properties or fuel mileage. It's more like pushing a 4X8 sheet of plywood down the road.The only Factory Jeep CJ to even come close to 20 MPG real world, was the 1980's 4 cylinder. Back in the day mileage was not much of an issue. My rig gets about 9 MPG, but then again it's far from stock. I love the simplicity of a carburetor, but port fuel injection is better for mileage. You have to keep in mind the cost of modification to the price of fuel. What is your ultimate goal for your Jeep? I know I'm full of questions, not to mention what else.

 

[coldwater]

I hope your not talking German highway speeds. I did some TDY in Bad Tolz. But seriously, some more specifics would help. Like final drive ratio your running, Tire size, are your engines stock? A CJ is not know for their aerodynamic properties or fuel mileage. It's more like pushing a 4X8 sheet of plywood down the road.The only Factory Jeep CJ to even come close to 20 MPG real world, was the 1980's 4 cylinder. Back in the day mileage was not much of an issue. My rig gets about 9 MPG, but then again it's far from stock. I love the simplicity of a carburetor, but port fuel injection is better for mileage. You have to keep in mind the cost of modification to the price of fuel. What is your ultimate goal for your Jeep? I know I'm full of questions, not to mention what else.

That's what I'm talkin bout!

 

[LongHorn]

You have to keep in mind that EPA mileage estimates in those day were wildly overstated. Also the estimate is for a skinny tire equipped 4 cylinder rig with no power steering & no A/C, probably running down a 40 percent grade.

 

[mylittlecj5]

For mileage/hiway capability, and a decent off road gear, I'd stay with the gears you have, and throw a NV3550 or NV4500 in there.
Low first gear and an O/D for cruising in a pretty bulletproof package.
Maybe toss in a low gear set for the Transfer Case and you will be able to cruise the hiway all the way to the trail, and have the gears to conquer it!

Thats kind of my ultimate goal if funds ever get high enough ( )

 

[LongHorn]

For mileage/hiway capability, and a decent off road gear, I'd stay with the gears you have, and throw a NV3550 or NV4500 in there.
Low first gear and an O/D for cruising in a pretty bulletproof package.
Maybe toss in a low gear set for the transfer case and you will be able to cruise the hiway all the way to the trail, and have the gears to conquer it!

Thats kind of my ultimate goal if funds ever get high enough ( )

Now I'm not trying to get the fur flying again, but I just don't see the point.
NV3550 Specs at a Glance:
Make: New Venture Gear
Length: 16.7"
Height:
Weight: 97 lbs.
Case: Cast aluminum
PTO Port: None
Mfg. Torque Rating: 300 ft. lbs.
Gear Ratios (Jeep): (x-to-1):
4.01 2.33 1.39 1.00 .78 R3.57
Most late model CJ's run 3.23 -2.73 final drive. You be the judge.

 

[Petescj]

Are you really only getting 10 mpg or exagerating a bit ? With my 360 and the same combo Im getting 14mpg city. If you are Id recomend ignition upgrades for both of them. Id also check how rich your carbs set up. I dont think the Transmission is whats holding you back. I can cruise 65-70 all day long with 33s and 4.10s. The T-150 is pretty questionable as a off-road Transmission as far as rock crawling. With the Dana 20 and T-150 it just not geared low enough. I like the T-176 Dana 300 combo out of the 80s Cjs myself.

Hi everyone. Thanks for all of the info. I'm TDY in Germany right now, so I haven't had a lot of time to reply to any of the postings. What I'm actually looking to do is replace the 3 speed T-150 with something that would allow me to reach highway cruise speeds without burning 10MPG in fuel. Right now the two Jeeps that I have both have the T-150 trans, the 1975 CJ-5 has a 304 V8 and the 1979 CJ-5 has the 4.2L 258 I6. Just to recap, I'm basically trying to find the best/easiest way to make driving at higher speeds a reality while maintaining the ability to use it off road. Thanks!

 

[mylittlecj5]

Now I'm not trying to get the fur flying again, but I just don't see the point.
........
Most late model CJ's run 3.23 -2.73 final drive. You be the judge.

You don't see the point of a 5 speed Overdrive Transmission with a reasonably low first gear? Then I can't explain it, sorry! (did I miss something or is that a T-18 chart up there, not a NV 3550)

For the record, the OP doesn't say he is rock crawling or doing anything technical. So the 4.01 first seems like a good compromise for street and trail use. The .78 5th gear will help out the mpg on the freeway. Is that not what he wanted to hear?
Combine that with the low Transfer Case gears for anything more technical/needing more control.
Also the OP has a 75, which could (should?) have 3:73 gears (just like my '74). The '79 could have ratios like you mentioned, true.
Now, I will admit I read more than wrench, so I may be way off. But people a lot better at this than me have done this and been pleased enough to post it on the WWW to share with the world.


BTW thanks for posting those charts, I didn't feel like looking up all the info myself!

 

[LongHorn]

You don't see the point of a 5 speed Overdrive transmission with a reasonably low first gear? Then I can't explain it, sorry! (did I miss something or is that a T-18 chart up there, not a NV 3550)

For the record, the OP doesn't say he is rock crawling or doing anything technical. So the 4.01 first seems like a good compromise for street and trail use. The .78 5th gear will help out the mpg on the freeway. Is that not what he wanted to hear?
Combine that with the low transfer case gears for anything more technical/needing more control.
Also the OP has a 75, which could (should?) have 3:73 gears (just like my '74). The '79 could have ratios like you mentioned, true.
Now, I will admit I read more than wrench, so I may be way off. But people a lot better at this than me have done this and been pleased enough to post it on the WWW to share with the world.


BTW thanks for posting those charts, I didn't feel like looking up all the info myself!

I'm sorry, I should have re-read the original post, I missed the year model. I'm not trying to sharpshoot your opinion. I tend to over build, because when I got started I scattered parts allover a five state area. IMO 300 lbs. ft. of torque rating is on the low side of the strength scale for V8 power. Again just my opinion for what that's worth. That's also why I asked for more detail on the setup he was planning to run.

 

[LongHorn]

You don't see the point of a 5 speed Overdrive transmission with a reasonably low first gear? Then I can't explain it, sorry! (did I miss something or is that a T-18 chart up there, not a NV 3550)

For the record, the OP doesn't say he is rock crawling or doing anything technical. So the 4.01 first seems like a good compromise for street and trail use. The .78 5th gear will help out the mpg on the freeway. Is that not what he wanted to hear?
Combine that with the low transfer case gears for anything more technical/needing more control.
Also the OP has a 75, which could (should?) have 3:73 gears (just like my '74). The '79 could have ratios like you mentioned, true.
Now, I will admit I read more than wrench, so I may be way off. But people a lot better at this than me have done this and been pleased enough to post it on the WWW to share with the world.


BTW thanks for posting those charts, I didn't feel like looking up all the info myself!

There are two charts 1.) for the Nv3550 2.)For the T-18 .

 

[Orionarms82]

I hope your not talking German highway speeds. I did some TDY in Bad Tolz. But seriously, some more specifics would help. Like final drive ratio your running, Tire size, are your engines stock? A CJ is not know for their aerodynamic properties or fuel mileage. It's more like pushing a 4X8 sheet of plywood down the road.The only Factory Jeep CJ to even come close to 20 MPG real world, was the 1980's 4 cylinder. Back in the day mileage was not much of an issue. My rig gets about 9 MPG, but then again it's far from stock. I love the simplicity of a carburetor, but port fuel injection is better for mileage. You have to keep in mind the cost of modification to the price of fuel. What is your ultimate goal for your Jeep? I know I'm full of questions, not to mention what else.

Hey LongHorn, I'm at Ramstein AB on this trip. It's my first time to Europe (actually it's the first time the military didn't send me to a sand infested location) and it's beautiful over here. Anyway, Everything on both of the CJ's is stock. From what I can tell, there have been no mods done to either one. I'm not actually looking for fuel economy. When I said 10MPG I meant that when you are driving 50-60 MPH down the road you are pretty much maxed out and it would be dumb to try and run the RPMs higher. I'm probably going to leave the '79 Jeep the way that it is and use it off road or whatever, but the '75 Jeep was restored about 5 years ago and it has been treated with POR-15 and also has a fiberglass body. I basically love driving both of the Jeeps the way that they are, but I love the way CJ's look and I was just trying to find a way to upgrade the '75 Jeep CJ5 with something that would allow me to go from the around town speeds 50-55MPH to something like hopping on I-95 and going to Savannah if I wanted to. If that isn't really something that is easy to do, I'll probably just sell the '79 and buy a newer Jeep that can drive on the highway easier and use the '75 CJ5 to take the top off on nice days and drive the 50-55 MPH to Myrtle Beach from my house (20 miles or so). Both Jeeps are pretty much toys, but if this is something that I decide to do, I want it to be reliable and hopefully not very complex (I'm not very experienced in this area of mechanics). Thanks! Now back to the German Hefeweizen Beer!

 

[Petescj]

Not cheap , but ready.

NV4500 CONVERSION JEEP CJ TJ YJ 4CYL 6CYL V8 GM DODGE:eBay Motors (item 220464312998 end time Aug-15-09 10:00:31 PDT)

 

[LongHorn]

Hey LongHorn, I'm at Ramstein AB on this trip. It's my first time to Europe (actually it's the first time the military didn't send me to a sand infested location) and it's beautiful over here. Anyway, Everything on both of the CJ's is stock. From what I can tell, there have been no mods done to either one. I'm not actually looking for fuel economy. When I said 10MPG I meant that when you are driving 50-60 MPH down the road you are pretty much maxed out and it would be dumb to try and run the RPMs higher. I'm probably going to leave the '79 Jeep the way that it is and use it off road or whatever, but the '75 Jeep was restored about 5 years ago and it has been treated with POR-15 and also has a fiberglass body. I basically love driving both of the Jeeps the way that they are, but I love the way CJ's look and I was just trying to find a way to upgrade the '75 Jeep CJ-5 with something that would allow me to go from the around town speeds 50-55MPH to something like hopping on I-95 and going to Savannah if I wanted to. If that isn't really something that is easy to do, I'll probably just sell the '79 and buy a newer Jeep that can drive on the highway easier and use the '75 CJ-5 to take the top off on nice days and drive the 50-55 MPH to Myrtle Beach from my house (20 miles or so). Both Jeeps are pretty much toys, but if this is something that I decide to do, I want it to be reliable and hopefully not very complex (I'm not very experienced in this area of mechanics). Thanks! Now back to the German Hefeweizen Beer!

What size tire are you currently running? You might be able to run a taller tire to effectively reduce your final drive ratio for a higher top speed. Or lower cruise RPM. Also like Pete said a good full tuneup never hurts. What is your RPM at 55 now?

 

[LongHorn]

Hey LongHorn, I'm at Ramstein AB on this trip. It's my first time to Europe (actually it's the first time the military didn't send me to a sand infested location) and it's beautiful over here. Anyway, Everything on both of the CJ's is stock. From what I can tell, there have been no mods done to either one. I'm not actually looking for fuel economy. When I said 10MPG I meant that when you are driving 50-60 MPH down the road you are pretty much maxed out and it would be dumb to try and run the RPMs higher. I'm probably going to leave the '79 Jeep the way that it is and use it off road or whatever, but the '75 Jeep was restored about 5 years ago and it has been treated with POR-15 and also has a fiberglass body. I basically love driving both of the Jeeps the way that they are, but I love the way CJ's look and I was just trying to find a way to upgrade the '75 Jeep CJ-5 with something that would allow me to go from the around town speeds 50-55MPH to something like hopping on I-95 and going to Savannah if I wanted to. If that isn't really something that is easy to do, I'll probably just sell the '79 and buy a newer Jeep that can drive on the highway easier and use the '75 CJ-5 to take the top off on nice days and drive the 50-55 MPH to Myrtle Beach from my house (20 miles or so). Both Jeeps are pretty much toys, but if this is something that I decide to do, I want it to be reliable and hopefully not very complex (I'm not very experienced in this area of mechanics). Thanks! Now back to the German Hefeweizen Beer!

I went back & read your original post, it seems so long ago now. If you have Limited mechanical experience & or tools, I would probably steer clear of a Transmission swap altogether. Not to mention the large expense. I'm surprised that the 79' won't cruise at 70. I would think the final drive ratio should be 3.54 or 3.23. Again It would be helpful to know your current RPM at 55 mph. To change the subject the main thing I miss about Germany is the great!!!!!

 

[CJ]

~~~ I'm not actually looking for fuel economy. When I said 10MPG I meant that when you are driving 50-60 MPH down the road you are pretty much maxed out and it would be dumb to try and run the RPMs higher. ~~~

Are you sure about those mileage numbers?

My 72 with 3.73 gears and 31" tires running 65 MPH got about 16mpg.


As was asked before, we really need to know your gear ratio, tire size and such.

 

[BrockGrimes]

I have a '79 with a AMC 258 i6 / 4.2l and T-150 running 33"s and I top out at 70 - 75mph.
Not Idea on gas mileage, never check.
I also run 33x14.50 tires So the extra width keeps it stable at those speeds.

 

[BajaEdition]

I was going say to keep it stock if 75 is the goal, but then I thought about how short a CJ5 is and how fast 75 was and wondered if a CJ7 might be in the future? I have a CJ6 , 101 inch wheel base I have set up to hit around 80, no problem as it has a long wheelbase. Use my CJ5 for trail duty, and not to fast to the trails.
But that is just my opinion, what is good for me may not be the best for you.
But I will say, if MPG and speed is the issue, keep it as stock as possible.