will a 5.3 from a impala or grandprix bolt on to my 5 speed getrag tranny or will i just be better off going with a northstar engine wich would be better a 5.3 or a 4.6 n*

I'm not an expert on this but i believe mating the getrag to an ls4 would be very difficult due to the lack of a way to mount a starter. If you want a manual another engine would probably be a better place to start. I'm sure others know more and will give input on this though.

[This message has been edited by GraterFang (edited 07-26-2010).]

The bolt pattern for the bellhousing should let the Getrag mount to it, but there is no place on the block to mount the starter. The engine was only offered with an automatic, a special casting of the 4t65e-HD bell housing, with a transmission-side starter mount.

This is one reason why all the LS4 swaps that have been done, retain the 4t65e-HD it comes with.

quote Originally posted by dobey: But if you're thinking of doing it for the DoD, you won't be able to use the DoD with a manual trans very reliably. You will absolutely hate driving it, if you can manage to get it to play right.

There are only 3 qualifiers to enable DoD (at least for 2007 - gear, range switch and one other) that are transmission related (the other 15+ are engine specific or non-tranny) so I wouldn't rule out DoD with a manual as a possibility. There will probably be some type of surge when it engages/disengages and you might be able to soften this if you momentarily applied pressure to the clutch and allowed it slip (GM loosens up the TCC on the auto to mask this transitionary state). Or it might not "feel" that bad... and feel is a purely subjective opinion with everyone being different.

For me, I would love a LS4/F40 that retained DoD that would only work at 55+mph on the highways/interstates and would probably put up with some amount of shudder now and then for 30+ mpg... Plus now there is a way you can turn it off with a switch if you are not in the mood to deal with it on any given day...

i came here from the LS4 forum on LS1tech. i talked to a few people there that are doing a LS4 swap on these cars they told me that i will need to find a way to mount the starter but it can be done with a little bit of time and money. but most people stay with the trans the ls4 comes with.

quote Originally posted by fieroguru: For me, I would love a LS4/F40 that retained DoD that would only work at 55+mph on the highways/interstates and would probably put up with some amount of shudder now and then for 30+ mpg... Plus now there is a way you can turn it off with a switch if you are not in the mood to deal with it on any given day...

Well, my goal is to get better highway mileage than 30, without DoD.

with the LS4?

quote Originally posted by hawkins04: with the LS4?

Yes. I'm doing LS4 + F40 trans.

It shouldn't be much of a challenge.

i dont think you can get over 30 mpgs with the LS4 without DoD?

quote Originally posted by hawkins04: i dont think you can get over 30 mpgs with the LS4 without DoD?

Sure you can. I'd actually like to get over 40 with it. At 80mph in 6th gear, I should be running about 2350 rpm. That would probably be over 30 mpg.

yea i keep thinking of a 4 speed like i have in my grand prix sorry. you should be seeing atleast 40 mpgs with that

quote Originally posted by hawkins04: yea i keep thinking of a 4 speed like i have in my grand prix sorry. you should be seeing atleast 40 mpgs with that

It depends. If I knew wha the pulse width would be at that speed, I could get a much more accurate number. 30+ mpg shouldn't be too hard to get with it. 40+ will probably be a lot harder.

Look at it this way. The '98-'02 LS1/T56 Camaro could do 31 mpg doing 1450 rpm at 65 mph. The F40-MT2 on 26" tires is more like 1850 rpm, but the 5.3L is 21 cubic inches smaller. 30 should be easy, but 40 will never happen.

quote Originally posted by hawkins04: yea i keep thinking of a 4 speed like i have in my grand prix sorry. you should be seeing atleast 40 mpgs with that

that 4 speed more than likely has a taller top gear than the 6 speed F40, no? whats the overall final drive in your tranny?

The MT2 uses a 3.54545454545:1 final with a 0.6230:1 sixth. the econo version of the Fiero 4-speed manual uses a 3.32:1 final with a 0.73:1 fourth.

LS4 tranny's come with a 2.93 final drive ratio coupled to an overdrive 4th gear of 0.7. Engine is reving at ~1750 at 60 mph. The best mileage I ever recorded on the GXP was 35 mpg - mind you that is using real gallons, not US "gallons". So call it 28 mpg.

The 2.93 is actually 33/37 sprockets with a 3.29:1 final. But even lower cruise rpm is possible by replacing the 3.29 with either the 3.05 or the 2.86. If we figure 26.00" tires, ( such as 215/65r15s ) then 1509 rpm at 65 mph is possible.

You get to the point that revs are so low that you're lugging the engine. I ended up pulling a fair bit of timing out of the stock timing table in the 1,400 to 2,200 range because of knocking at moderate engine loads - mostly in fourth gear cruising....

the engine does shut off the same 4 cylinders everytime and thanks tiredgxp for the final gear info

quote Originally posted by TiredGXP: You get to the point that revs are so low that you're lugging the engine. I ended up pulling a fair bit of timing out of the stock timing table in the 1,400 to 2,200 range because of knocking at moderate engine loads - mostly in fourth gear cruising....

An LS4 will pull 1510 at 65. I've had an L35, in a fullsize pickup (which is heavier and has much more wind drag) with an automatic, pull 1610 at 65 up here in this thin air. That wasn't lugging. The LS4 adds 63 cubic inches. And didn't you notice I just reported that LS1 Camaros do 1450 rpm at 65 , with only 21 cubes more than the LS4, but with more weight, more drag, and wider tires. That's not lugging, either.
40 mpg from a stock LS4 sans DoD, with 1510 at 65, is more realistic.
As for you, don't pull timing, add more octane.

[This message has been edited by Isolde (edited 07-27-2010).]

quote Originally posted by stickpony: speaking of DoD: does anyone have evidence of the long term affects of DoD on the engine? and do the same 4 cylinders get shut off everytime? from a mechanical standpoint, i would think the engine will wear out in a non-conventional way over time..?

They are the same 4 cylinders every time. However, I don't think there is any additional wear on most of the engine components. The valves just stay shut, the plug doesn't fire, and the pistons just compress/decompress the air in the cylinder, to bounce the pistons and help keep things moving. The DoD lifters might wear more if DoD stays engaged for most of the engine's life, or if it is engaging and disengaging very often. Having the DoD cylinders stagged the way they are, helps maintain balance, and keep things rotating smoothly (outside of the sudden switch, but the engine/trans controls are set up to smooth that out too).

quote Originally posted by Isolde: An LS4 will pull 1510 at 65. I've had an L35, in a fullsize pickup (which is heavier and has much more wind drag) with an automatic, pull 1610 at 65 up here in this thin air. That wasn't lugging. The LS4 adds 63 cubic inches. And didn't you notice I just reported that LS1 Camaros do 1450 rpm at 65 , with only 21 cubes more than the LS4, but with more weight, more drag, and wider tires. That's not lugging, either. 40 mpg from a stock LS4 sans DoD, with 1510 at 65, is more realistic. As for you, don't pull timing, add more octane.

the 5.3 in the trucks are different than the 5.3 in the cars

Maybe, but the 5.3 in my '05 tahoe is spec'ed pretty close to the ls4, and it happily locks up the torque converter at just over 1100 RPM, and it doesn't lug.. In fact, it's downright smooth. It's amazing how smooth that motor is.

quote Originally posted by Isolde: As for you, don't pull timing, add more octane.

Already at the highest octane that is readily available around here. Timing was only pulled in the cruise cells of the map, so no impact on acceleration.

quote Originally posted by hawkins04: the 5.3 in the trucks are different than the 5.3 in the cars

L35 isn't 5.3, it's 4.3

quote Originally posted by TiredGXP: You get to the point that revs are so low that you're lugging the engine. I ended up pulling a fair bit of timing out of the stock timing table in the 1,400 to 2,200 range because of knocking at moderate engine loads - mostly in fourth gear cruising....

i would think that the fiero, being 800+ lbs lighter than a gxp, wouldn't have those issues, yes?

quote Originally posted by stickpony: hh, that still sounds like speculation to me... i would like to see compression tests after 150k-200k miles, and also a teardown to see if the wear is even across all 8 cylinders... has anyone done this to a high-mileage ls4?

Well, on the engine with 10k, the wear looks pretty even. And it looks more worn than I would expect for 10k. Not sure why, though. You never really know when you buy an engine from a yard. I think the highest mileage I've even seen for an LS4 on ebay/etc... has been around 65K. The ones that have 100+K are probably still on the road, and being driven by old people. And they're probably the Buick Lacrosse Super version. I don't think I've ever seen an LS4 out of a Buick on ebay or anywhere.

quote Originally posted by stickpony: i would think that the fiero, being 800+ lbs lighter than a gxp, wouldn't have those issues, yes?

I was having those thoughts too.