: WOT vs 4T80E vs. Timing Chain



mtflight
04-19-05, 01:05 AM
I recently moved my seat an inch forward, so I could feel the carpet :devil: behind the accelerator pedal (you know what I mean). Now it's almost tempting to give it some juice more and more often. WOT is good for the Northstar, but how much is too much? BUT!!! What kind of stress do the transmission and timing chain go through during WOT acceleration?

Maybe I'm paranoid, no, I take that back... I AM paranoid. I'd like my Northstar to last through the 100K barrier, and beyond (maybe 200K). I'm taking care of the cooling system (pellets, and replacing coolant every year), and the tranny (replaced fluid too @68K)


Basically speaking, variable RPM wear the engine more than a steady pace (that's why highway miles are supposedly better than city miles).

What kind of stress does the timing chain undergo? Are they no issue?
Is a belt better than a chain? Why do we have a chain in the Northstar? I haven't heard about any issues with the timing chain, so it must be very robust, but I need some peace of mind.

Regards,

Alex

JimHare
04-19-05, 07:17 AM
I'm sure more expert members than I will chime in, but from what I've read here, the 4T80E is a very robust piece of work, and should be designed to take anything your N* can dish out, within reason (I wouldn't do too many 6000 RPM From Neutral-drop-it-into-Drive shifts...) If you follow the recommended methods for WOT exercise, barring any other faults, the trans should be just fine.

And from what BBob and others have written, the timing chain is pretty much indestructable.

CTX-SLPR
04-19-05, 09:12 AM
The big difference is that with DOHC you need really accurate timing so that all the cams stay in sync. A chain will stretch but not nearly as much as a belt will do over the course of its life. A chain however will fatique instead of stretch but considering a belt is a rubber encased piece of nylon or metal cloth and a chain is steel links the fatique life is pretty high.
Belts also can cause valvetrain resonance for whatever reason, case in point, the Chevy IRL V8 has DOHC but also runs on chains vs the older Olds IRL DOHC V8 that ran on belts.

Thanks,

eldorado1
04-19-05, 10:59 AM
What kind of stress does the timing chain undergo? Are they no issue?
Is a belt better than a chain? Why do we have a chain in the Northstar? I haven't heard about any issues with the timing chain, so it must be very robust, but I need some peace of mind.


Very little..... Basically it just experiences the strain from the rotational inertia of the 4 cams. IMHO, a chain is better than a belt. Belts are used when engine noise is to be kept at a minimum, and then belts become a maintenance item. On the 3.4DOHC, it's recommended the timing belt be replaced every 70k or so. On the northstar, you should never have to replace the timing chain.

Your transmission will be fine too. Do you think the engineers built pansy cars that couldn't be raced? No! They overbuilt everything so when Joe sixpack takes it to the track every weekend, it won't blow up.

1996deVille
04-19-05, 11:36 AM
Go up to the "V" section and tell me that these cars are engineered not to "blow up"! Notice how many diffs have been replaced - many times over, in some cases!!!

Your tranny will work fine under "normal" driving conditions - but I wouldn't do WOT's from a standing start, you'll kill it quickly. Put it in 2nd gear, run it up to 6K and get off it... put it back in OD, set the cruise and hope you don't blow a head gasket.

The timing chain is the least of your worries in this car mainly b/c it is not a belt, thank goodness for that. Can you imagine having to pull the engine just to get to a timing belt?

eldorado1
04-19-05, 01:41 PM
Go up to the "V" section and tell me that these cars are engineered not to "blow up"! Notice how many diffs have been replaced - many times over, in some cases!!!


http://www.cadillacforums.com/forums/showthread.php?t=37043&page=1&pp=20
Are you referring to this?

There are always going to be problems with the first generation of cars... Would you like some examples?

CadiJeff
04-19-05, 02:08 PM
floor it and enjoy
the northstar/4t80e isn't a built up chevy piece of crap like the ls2 the tranny can take it and the northstar was built for high rev abuse unlike many other engines.

dkozloski
04-19-05, 04:05 PM
FWIW, roller chains do not stretch, period. The chain will wear at the joints and over time it will measure longer due to the accumulated slack but the links themselves do not stretch. I suppose there are some exceptions due to extreme failures or accidents that can be cited but in the normal course of events chains do not stretch.

danbuc
04-19-05, 10:21 PM
Let's put it this way. The L37 N* you have in your ETC makes it's peak hp at 6000rpm. This means, that in order to reach the claimed 300hp, the tranny had to be able to handle it. It was meant to be driven hard, and fast. DOHC engines by nature I high revving. WOT from a standing start, should only hurt your tires. The only real danger, is allowing one wheel to spin freely (such as while flooring the car around a turn from a dead stop). This can cause damage to the differential. In a straight line however, the tranny should be just fine. I wold recommend that you floor the gas at every stop light, but every now and then should be fine. On the highway is fine as well. That would be the best place to do it.

Pjs
04-20-05, 05:48 AM
I've had my 95 SLS for just over a year now...she gets WOT everyday. She just loves to make an entrance...on the freeway. I love the look everyone has on their face as she blows past them wide open...."Was that a cadillac???". She just turned over 145K. Had the engine opened up at 137K for bottom end seals. The cylinders looked great and the timing components showed virtually no more wear than break-in. She's got new rod bearings only because you can't reuse the old ones..but she's still sporting her original main bearings. Floor it...let 'er rip..enjoy the car for what it was made to do :D