Better mileage? nv4500 or 700r4?

[Redwookie]

Ok so attempt 2 at my poll here, sorry folks. Ok so my 89's tranny went finally. I'm switching the gas motor to a 6.2 when it dies but for now doing the tranny since it just died. For value/gas mileage is it worth it for me to go from a 700 to a nv4500 or is the real world mileage really close? Thanks!

 

[bp71k5]

They both have overdrive so I can't see how there would be any difference. Manuals tend to have better mileage because of the lack of torque convertor don't they?

 

[blazinzuk]

Yah its like having the torque converter lock up in every gear as soon as you put it in, torque converters have some slip in them, so in every gear but overdrive you will some slip you won't have in the manual trans.

I would think you would get better mileage out of the NV4500, if you get one that is rebuilt properly the reliability will go way up plus you have the advantage of the low first gear.

 

[Redwookie]

So maybe the only disadvantage you guys think the NV might have is perhaps the cost of buying the unit vs a rebuilt or new 700 right? Would the difference in mileage be worth it if to you? I mean I can afford the NV but if it's an extra 5 grand to do compared to the 700 and you average a 1/4 mpg better is it worth it?

 

[lectric80]

In general you have around 12-14% power loss in a manual, whereas an auto loses 17-22% due to inefficiency of the torque converter. When you see fuel mileage numbers, you will always see higher numbers with a manual than an auto. But, you have to know how to maximize the fuel numbers which is in how you drive.

These are of course approximate numbers, but they have been thrown around many times in my years.

 

[Redwookie]

Thanks for the info. It's much appreciated. So any thoughts folks on where to pick up an nv4500 for a good price and of course the gear ratio would need a nice low gear and then an OD that was equivalent to the one in a 700 or so right? Where do you find that?

 

[lectric80]

My understanding is all NV4500's are going to have the low 1st gear and overdrive that is about equivalent to the 700r4. As to where to pick one up cheap, I will let those with more knowledge than me point you in the right direction. When I want/need something, it tends to fall into my lap for a screaming deal, and I am not ready to convert Krusty to a manual trans.

 

[str8axle55]

From what I understand, only the earlier yrs had the low 1st gear, only a couple yrs. I would also like one.

 

[Redwookie]

Well I have to imagine then if I was to buy from a company that does them you could get one as wanted. I found a web site that sells them. It claims you can get them with a low 1st gear and a 27% overdrive. Here's a link but I dunno if they are any good or if the price is ok at all?

http://www.tellico4x4.com/product_info.php/cPath/2880_508_6461_518_3141/products_id/38485

 

[lectric80]

I know nothing about the company, although the name looks familiar. I would say the prices are on par with a well built 700r4 from BTO, but none of the GM versions list an output shaft count to know which TC will work behind them. 27% overdrive is almost exactly the same as the 700, and the 700 has a decent first gear, so it would depend on whether those prices include the low first gear.

 

[Redwookie]

OK I actually changed the link above. Now it's linked to a custom order form for the NV4500. You can order it with any of a list of options from drag down menues. It lists as few hundred more but it looks like you can have built specifically for Blazers which is cool. Might have to give these guys a try...

 

[lectric80]

Make sure you give it time to hear from the more knowlegable members. I have never dealt with the NV trannys, so I am by no means an expert.

 

[Redwookie]

Oh I suppose that last post sounds like I already made up my mind a bit doesn't it? Yeah I'm definately waiting for some more opinions first. Thanks for your help though Lectric. So who else has some opinions? Anybody?

 

[bp71k5]

The gm trans will have a 32 spline output shaft so you will need to make sure your transfer case will mate to it.

The big expense is going to be switching from auto to manual. You might need new driveshafts, move crossmembers, buy transmission adaptors, lots of other stuff. You can read through my build thread in the firstgen forum for my issues, and I used a few other peoples threads to guide me.

IMO, you should only switch to the manual, if you really want a manual. A 700 swap will be much easier, and if you get it built right, it'll probably be fine.

 

[Blue85]

When looking at the cost, be sure to include whatever adapter you may need to mate to your transfer case, the flywheel, clutch, clutch linkage and pedal, crossmember, etc. And look at the overall length. If it's much different, you are looking at having the driveshafts retubed.

Seriously, this will not be a case where you "save money" by swapping. Even if you went from 12 to 12.5MPG (optimistic), at 10,000 miles a year, you are saving 33 gallons of gas - about $83 a year. So spending a few hundred on the swap takes more than 3.5 years just to break even.

(Now I know lots of people happy to be "saving money on gas" with their new cars, but I just can't figure out how a $350/month payment saves money when I spend less than that in total on gas for all 3 of my (paid off) vehicles. But this is another topic...)

The real question is which transmission do you prefer - auto or manual? Some members have burned up a few 700s and went manual just to avoid more problems. Both have their pros and cons.

 

[Thunder]

I vote to keep the 700. to me its just not worth the hassle to go from a 700 to Nv4500 for maybe a very small increase in gasMPG. Personally i dont think you will see much because the 700r4 has a lock up torque convertor.
If you really want a manual then go for it. But for gas mpg its not worth it.
IMO a 700 better trans for offroading. But thaat is just my preferance Because I dont really like shifting all the time. Rather let the trans do the work and have both hands free.
Also along with the many parts mentioned for the swap already. You will need a new bell housing too.

 

[6.2Blazer]

Like said above, if the main goal of swapping is simply for fuel mileage than I wouldn't bother with the cost or hassle. If you simply want a manual then go for it, but I doubt you would ever see an appreciable change in cost of operation in regards to fuel.

In regards to needing the "low gear", all NV4500's have what is considered a "granny low" 1st gear that you don't use for normal driving. There were a couple different 1st gear ratios, but all are a granny low (thinking maybe abour 6.3:1 vs. 5.8:1).

 

[bp71k5]

I agree the mpg difference won't be noticable. The first gear is also only useful for towing or offroad situations. I don't ever use first gear on the street.

 

[Redwookie]

Well thanks folks keep the opinions coming! I am thinking maybe 700 now! Sheesh well my preference is really for an auto but then I really like the sturdy care free operation of the manual plus gas mileage improvements are nice. Not as concerned with the cost of the install at all, I can afford either, it's just truly I like the auto for ease of driving but I like the mileage and strength of the manual so which way do I go!?!?!? Sheesh...

 

[bp71k5]

it's just truly I like the auto for ease of driving but I like the mileage and strength of the manual...

Stick with the auto then. I also forgot to add the cost of the lube for the nv4500 is close to $150, but is supposed to last 100k. The mileage advantage would be very small.