Real MPG experience with 5.3L (TH350 and/or NV4500)

[Aruba1]

I am looking for some input in regards to the MPG for a stock 2000 5.3L Vortec engine running standalone (EFI) with 4:10 ratio.

The 5.3L is bolted on to a stock TH350 in the donor truck. I am debating between running a TH350 or a 1997 NV4500. The former would be an easier swap because I will just leave the old one in place and bolt the engine to it. The NV4500 is more work because I need to install a high hump floor and do some fabrication. I have all the necessary parts to do either install (special flywheel, clutch, etc).

My main question is towards MPG. What are you seeing with a TH350 or a NV4500 and what gear ratio do you have? Please limit discussions only if you have real experience with either swap.

[Nitis]

Well I'm guessing you would get better mpg with the handshaker but like you say is it worth the hassle?

I know that the 4500 is a hot item it could pay for a great deal of your swap or buy plenty of gas to cover the difference.

I'm along for the ride to see if you get some real world numbers as one option I consider is LS in front of my th350

[Aruba1]

I spoke with my uncle last night. He is a mechanic and when I told him about my dilemma of a quick swap with the TH350 or go with the NV4500 he said there should be no question about it, go with the NV as it will have better gas mileage and it will pull better than the TH. He said the swap itself takes a few more hours or a whole day but at the end I will worth it.

My truck has the low hump and the is the last thing on my swap list to purchase is the high hump tunnel. If anyone has a good deal on one, please PM me with a price shipped to 35133. I can make mine work but I rather do it right. I also need a clutch pedal :-). Thanks.

[enaberif]

The NV4500 will be the better choice but remember its a truck transmission and will shift like so.

Also don't forget about all the little extras that need to be done like driveshafts and crossmembers.

[Aruba1]

Thanks for the heads-up. I lucked out when I purchase the tranny as it came with clutch assembly, the two drive-shafts, shifter, clutch reservoir, lines, etc. I will be pulling a gooseneck with the truck so the truck transmission will work perfect.

My uncle has a good friend in town that shortens drive shafts for a living and he can get him to do for next to nothing. As for the crossmember I will be build something similar to this picture.

[67ChevyRedneck]

You couldn't have asked for opinions on two more different transmissions... one is a non overdrive automatic and the other is a 5 speed manual overdrive

Overdrive will always win for me... especially with a modern 5.3L, they're happy in the lower RPM range.

[Aruba1]

I know Jesse, and that is why I had to ask the question. If they were almost the same transmission then the TH350 would have been a no brainer :-). I can't wait to be driving the 72 with a 5.3L backed by the NV4500 gearbox. Who know, if I come across a nice transfer case I may install it too and at least have a good foundation to become a 4x4.

[RichardJ]

I agree with 67chevyredneck. A question asking about using a 700R4/ 4L60 verses a NV 4500 would have made a lot more sense.

>>My main question is towards MPG.<<

The main problem you have is the 4:10 gears. Only a choice between something like the 700R4/ 4L60 or a NV 4500 addresses that problem.

[MARKDTN]

I just have to ask the question. Why not a 4L60E or a 4L80E? If you are doing the swap anyway, why not an electronic overdrive trans?

[Aruba1]

The LSX donor truck that I bought already had a Current Standalone Harness, Fuse Box and PCM programmed for a TH350. If I went with a electronic transmission I would need to reprogram the PCM and splice into the harness. Also I already had a NV4500 laying around in the garage so why not use it.

[67ChevyRedneck]

Yup, definitely go for it. Both my toys have OD, and I drove them both for at least a couple years each without OD (ironically truck was a 3spd I swapped to an auto and the car was a C4 auto I swapped to a manual - go figure - but NV4500's were stupid $$$ in 2002 when I did my 700R swap). My C10 has a 700R and my 65 Mustang has a 5 speed T5. My 67 firebird project will be getting a T56... someday...

[Aruba1]

The other day they had a T56 for sale on CL for $600 that needed rebuilt. A day later I pulled the ad and it sold. Currently they have a 2003 NV5600 that doesn't go in ANY gears (bad clutch is the only thing that comes to mind) for $300. I am very very tempted to buy it but that will put me back about a $1000 just for a decent clutch. But a 6 speed behind the 5.3L sounds very awesome.

[67ChevyRedneck]

I got my T5 for $125, then spent ~$450 rebuilding it (after getting into it, it needed a reverse idler gear and 1-2 slider). It was my first trans rebuilt, it's gone almost 10K miles so far... so good...

[Aruba1]

I am glad I did not drive the LSX donor as the PO had done a bad job with the swap. The front cross member was severely butchered in order to fit the LS motor. The PO used the required spacer for mating the TH350 to the engine but for some darn reason he shimmed the spacer with double washer to move it closer to the tranny and then he used 5-6 spacers between the torque converter and the flex plate. If that was not all, he also torched the flex plate (I reckon the holes did not align with the torque converter so he welded put new holes by welding washers to align it, lol). All bolts and washers were grade 5. Horrible job.
The motor has about 125k miles according to the PO but I went ahead and removed the rear engine seal to install a new one. Hope to do some work the motor tonight and clean it up for some pictures :-).

[Aruba1]

Here are some pics folks. First one is the flexplate that the PO Hacker, lol, hacked. My best guess is that he did not have it balanced. Oh well, that one goes in the trash sans the adapter.

Second pic is the special sachs NFW1050. With it I also had to purchase special metric flywheel bolts and metric bolts for the pressure plate.

Third pic of the motor. Once I get home I will get it cleaned and shiny but she is ready to go in her new home.

Fourth pic is the 1997 NV4500 tranny undergoing some cleaning. Also on the transmission is the special pilot bearing to compensate for the length difference between the LSX engine and the SBC.

[Andy4639]

2004 LQ4 6.0 with 4L80e transmission out of a chevy heavy duty. No mods other than headers. No internal mods at all. Guy said it had 85,000 miles on it.

I get about 16MPG on the interstate with a factory 4:10 gear set.

[Aruba1]

Thank you Andy, that is what I wanted to hear :-). I hope (fingers crossed) to get 18 mpg with the 5 speed OD and my feather-light right foot. Mine got the headers.