M715 Conversion....need advice

[Jonofthesprings]

I was, was being the operative word here, going to change my M715's Tornado and 4 speed out for a 5.3L Vortec and 4L60E trans. Now, I suppose some of you are fighting mad right now, however, it would have way more power with the 5.3L. But I am leaning more toward just swapping the engine, I like the 4 speed. Does any one have any advice for me as to why I should not make the swap.

 

[Recovry4x4]

I would have no problem with the swap but why the 5.3? Think I would opt for a more conventional small or big block with the Muncie SM465 behind it. Adapting a T98 to the 5.3 might prove troubling. I also would think the coputer operated 5.3 wouldn't be suited for such a simple vehicle as the M715. Where do you hail from? Need to have your location in your profile or signature.

 

[sermis]

I have a 350 in my M725 with the T98. About $500 for the adapter kit. Go with an OD trans of some kind. 6 mpg is killing me. Can"t get too much speed for long periods of time with the NP200 due to heat issues. 50 is about max to keep the heat in check. If you are going to the trouble of repower and trans, add in a NP205 and your done, and have a 65-70 mph rig plus if it is all married you can put all in at once and make the mounting eaiser.

 

[Jonofthesprings]

Thank you guys for both of your ideas, you have both given me a lot to think about. Kenny, I am from Moultrie...was not sure how to get that into my profile. Why 5.3, well you get a lot of power and torque, they run forever so buying one out of the junkyard with 100k miles or more is not a worry, and fuel injection has spoiled me. The SM465 would be nice. I like the sound of the 205 also, I also did not consider the overheating issues. This is why when you don't know...ask those who do. I can see I have found a wealth of knowledge with the both of you. I will be seeking advice as this continues to unfold. Thanks.

 

[mcinfantry]

run the 5.3 with the OD 5 spd 2wd. then a divorced 205.

 

[CGarbee]

Re: RE: M715 Conversion....need advice

Can"t get too much speed for long periods of time with the NP200 due to heat issues. 50 is about max to keep the heat in check.

HUH?? What heat issues?? I've been running a NP200 behind the Cummins 4BT/ZF S5-42 in my M37 for years at 75mph on the highway with no problems... I did swap out the seals for non-military ones that have a higher temperature rating then the mil-spec ones, but other than that...

Of course, the NP200 is a tad loud at 75mph, but then, the whole truck is...
Earplugs...

 

[mcinfantry]

RE: Re: RE: M715 Conversion....need advice

i ran my stock 715 for over a year at 65 with 200. never any problems either, unless noise is a problem

 

[sermis]

RE: Re: RE: M715 Conversion....need advice

Noise can be reduced by swapping the drive shaft to the e-brake output. I moved mine and it helped on the loud whine. NP200’s do not like high speeds for long periods of time. I have never checked the temp of my case after longer trips, 30+ miles at 60mph I can sure smell it being hot. Touched the outside of the case and almost burned my fingers. Barrman also has noticed heat from the case. Jump over to M715zone.com and post up. There have been several discussions about the heat issue with the NP200.

 

[gimpyrobb]

RE: Re: RE: M715 Conversion....need advice

From what I understand, some have troubles and some don't. I know mine is one that has trouble. Maybe a goofy batch of seals.

 

[sermis]

Re: RE: M715 Conversion....need advice

[/quote]

Cummins 4BT/ZF S5-42 in my M37 for years at 75mph

Earplugs...[/quote]

How are you getting that kind of speed with the 4bt?

 

[mcinfantry]

RE: Re: RE: M715 Conversion....need advice

overdrive and 4.89 gears

 

[Barrman]

RE: Re: RE: M715 Conversion....need advice

Running my 396/NV4500 powered 715 at 60 mph for 45 miles gets my t-case temp up to 260-270 degrees. Keeping it below 2000 rpm in 5th (54 mph) with the XZL tires lets the case temp stay around 210-220. I also did the center output conversion. I have put about 6000 miles on it driving like this and no seal leakage issues. I am running Mobile 1 synthetic in the case.

I have a divorced 205 and just haven't put it in yet. That is the best solution if yours heats up.

 

[mcinfantry]

RE: Re: RE: M715 Conversion....need advice

i agree with tim.
btw tim, call me sometime
225 445 6223

 

[yonder]

RE: Re: RE: M715 Conversion....need advice

I don't question your intention to change the drivetrain.

I question your choice in what engine to swap to.

Have you considered the Cummins 4BT?

 

[Jonofthesprings]

Re: RE: Re: RE: M715 Conversion....need advice

I don't question your intention to change the drivetrain.

I question your choice in what engine to swap to.

Have you considered the Cummins 4BT?

What do you think are the pros and cons of the 4BT?

 

[mcinfantry]

RE: Re: RE: Re: RE: M715 Conversion....need advice

initial expense is the only con.
everything else is pro

 

[gimpyrobb]

RE: Re: RE: Re: RE: M715 Conversion....need advice

Well, when your talking to someone who wants to keep the 4 speed, thats incorrect. If you use an overdrive trans and maybe re-gear they have no cons, but I would say limited rpm is a big con. I'm not saying I wouldn't want one, just need more than the motor for a 715.

 

[mcinfantry]

Re: RE: Re: RE: Re: RE: M715 Conversion....need advice

initial expense is the only con.
everything else is pro

initial expense is the only con. i.e. the cost involved of running a 4bt, which would include
1) the motor
2) the transmission
3) regear your axles ( better to swap them)

i apologize for my short answer.

i know of 0 instances where the rpm was a con

 

[Barrman]

RE: Re: RE: Re: RE: Re: RE: M715 Conversion....need advice

As you can see, we all have different thoughts on this issue. If you already have a 5.3/4L80E combination sitting on the floor of your shop. Put it in and see if you like it. Or, sell it and use the money to get what you really want. There really is no correct answer. But, try to look for this:

Over drive transmission 2wd

fuel injection

NP205 divorced T-case

Bigger tires or re gear.

Of course a diesel is going to be fuel injected. But otherwise the same stuff above applies to any engine. The end result no matter what kind of engine you install will be a vehicle that will go just about anywhere, pull/tow more than the brakes can stop and get 10+mpg gas and 20+ mpg diesel.

I just opened another can of worms mentioning the brakes. Just remember that every modification you do will have a trickle effect on the rest of the truck. Plan ahead, have fun and build the truck you want not the exact one we tell you to.

Lee, I got busy last night and didn't want to call too late. I should have a chance this evening.

 

[Jonofthesprings]

I think the consensus is it is a lot to think about all the way around.