hirdlej

iTrader: (31)

Can anyone fill in the blanks for me?

2004 6.0L crankshaft length =

2004 4.8L manual transmission crankshaft length =

2004 4.8L auto transmission crankshaft length =


The reason I ask is in a couple of weeks my 4.8L is coming out of my truck (equipped with a 5 speed) and my 6.0L Lq4 is on the stand. I read a post earlier tonight (can't find it now) where someone stated the 4.8L that had a manual transmission had a longer crankshaft. Is this true? I find it hard to believe.

kbracing96

iTrader: (26)

As far as I know, they are all the same in 04. it was only the early (99-00) 6l that had a longer crankshaft.

TurboGibbs

iTrader: (6)

That is my understanding as well. I'm unsure of the years that the 4.8 manual had the longer crank to fit the gen1/2 transmissions. It was just the early one's as well from what I remember.

hirdlej

iTrader: (31)

Time to get out my factory GM service manual. I hope it has this information in it. I'll post my findings.

hirdlej

iTrader: (31)

Ok, I'm gonna have a **** fit if I don't get this figured out soon as this project is either a GO in a couple of weeks or will have to be put off another summer to save up for a T56. Doesn't anyone here have a motor they pulled out of their 4.8L manual transmission truck? I just need the total crankshaft length measurement. My GM service manuals are not giving total crankshaft length specifications. I just need assurance that my 6L has the same length as a manual transmission 4.8L. Everyone who does a swap into a gibbs or rst truck seems to do the t56 at the same time so they'd probably never run into the problem I'm questioning about. I want to be the 5 speed guy For at least another year or two

TurboGibbs

iTrader: (6)

my 05 4.8 5 speed had the same length on the rear of the crank as my 6.0. Which is the same as the 4l60e cranks. The rear flange is almost flush with the rear seal. It can't protrude more than .25"-.5" past the seal.

hirdlej

iTrader: (31)

If what you state is true then I'm golden. This was bugging me so much last night I couldn't sleep. I pulled out my Helms GM Manuals and they had nothing for total crankshaft length specifications, also went to the GM service manuals online and nothing. I don't have the money or time for a T56 right now but I basically have spent my last "hidden dollars" (bank account wife doesn't know about) on this and was going to be mucho depressed if I couldn't get everything transplanted here in a couple weeks before I take the truck out of winter storage. I'm keeping the combo simple and hopefully I can enjoy my new found power and destroy a few muffstains err mustangs in the process. Final combo is going to be:

10.5:1 comp - .034 quench w .040 cometic MLS head gaskets
243 heads
stock LQ4 rotating assembly
OBX Long Tube Headers with single 3.5" exhaust to keep it stock looking
TR220 on a 114 LSA


That should make for a simple but yet stout street combo. I did intentionally keep this on the tame side to keep up the reliability along with making it a sensible daily driver. I won't ever have this combo dyno'd as I know it will lay down 370 RWHP and 380 RWTQ through my 5 speed. I will however go up to Brainerd international raceway once or twice this summer to see what it will lay down for times. Hoping I can click off or knock on the door of a 13 second flat 1/4 mile. Then this whole swap will have been worth it. 13.5's and I'm gonna think to myself it was a waste of money. As the truck runs now it's a 14.5 second truck with a Z06 cammed 4.8L. Anyways thanks TurboGibbs, this board needs more guys like you and that tidbit of information you gave me saved me more stress than you realize.

TurboGibbs

iTrader: (6)

Good luck! Your projected times sound doable with slicks. Remember, it is hard to get a manual to launch, even with slicks. You usually have to do a 5k or more dump to get one that is even geared properly to get it leave like an auto with a 3000 stall. With 5000 rpm + dumps you run into severe axle wrap issues if you don't have any traction divices which will break springs, housings, spider gears, axles, ujoints and driveshafts. Oh, and transmissions, pressure plates, rip the center out of clutch discs etc. I have been drag racing manuals for years and have broken all those items at least once and then some. A manual with 300 rwhp will break more drivtrain parts than an automatic with 600 rwhp.

1FastBrick

iTrader: (17)

Here is what I found online By Doug Anderson
http://www.enginebuildermag.com/Arti...all_Block.aspx

Crankshafts
There were only two different strokes used for the entire Gen III family, so the cranks should be pretty straightforward, but it's not that easy because there are two different flange widths and one crank that has three or four different bobweights to deal with.

4.8L Cranks
There are two cranks for the 4.8L, one with a wide crank flange (1.250?) and one with a narrow flange (0.857?). Although we don't know exactly what GM did, it appears that the '99-'00 trucks with manual transmissions came with the 12553312 casting that had the wide flange and the '99 - '00 trucks with automatic transmissions came with the 12553482 crank that had the narrow flange. All of the 4.8L motors used the crank with the narrow flange starting in '01.

5.3L Cranks
The 5.3L engines all came with automatic transmissions, so they all had the 12552216 casting with the narrow flange. This is the same casting that was used in both the 5.7L and the 6.0L, but it's balanced specifically for this application, so it has its own unique GM part number. We don't know what the bobweights are, but our sample piston weighed 406 grams.

5.7L Cranks
The 5.7L had the same stroke as the 5.3L, but the cars always with came the narrow flange, so it had the same 12552216 casting that was used for the 5.3L and 6.0L. The 5.7L cranks weighed about a pound less than the others because they had a 24.5 mm hole drilled right through the center of the second, third, fourth and fifth journals. We're pretty sure that the balance was unique to this application, because the pistons weighed 434 grams which is more than the 5.3L and less than the 6.0L.

6.0L Cranks
The 6.0L shares the same 3.622? (92mm) stroke with the 5.3L and 5.7L, but there are two or three different cranks.



All of the '99 - '00 cranks had the 12552215 casting with the wide flange. This is the only application for a crank that has a 92mm stroke and a wide flange.


All of the '01-'04 cranks used the 12552216 casting with the narrow flange, just like the 5.3L and 5.7L, but the 6.0L pistons weighed considerably more (470 grams) than the ones used in the 5.3L and 5.7L engines, so the bobweights had to be different. These may even be two different versions of this crank because the rods used in the LQ9 motors weighed 36 grams more than the ones in the LQ4 motors

shakinlm7

iTrader: (5)

I'm not saying that that any of the info is wrong because I don't have a clue but I read the whole post and the chamber size they have listed for the 708 heads doesn't match up with what I have seen on other posts.