If you have a 99 4wd odds are that you already have a 4r100 in it. The only difference is that the L's use the diesel version of the 4r100. If you have the means and you want to make yours shift a little firmer you can get the governor body from a diesel 4r100 and stick it in yours.

Besides beefed up internals the L 4R has the 6 bolt flywheel just like the diesels also.

I had to have mine torn down at 3000 miles- I didnt have engine breaking from day one and it turned out that they didnt seat the snap ring in the coast clutch so it was just floating around in there grinding things up.

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Struck by Lightning
Lightningstruck9@aol.com

Furthering the American Quest of Unlimited Horsepower and Crappy Gas Mileage!

 

no no no, if you have a 4WD 99 you prolly don't have the 4R100, unless it's a CA emissions vehichle. And the difference between a diesel and a modular 4R100 is the case not the innards, I've always hated whoever said it was a deisel transmission in a gas case, cause there are 13 versions of 4R100s in a modular case. The Lightning box does get a 6 bolt converter, but so do all the v-10 models. And don't go trading accumulators and valve bodies from one model to another unless you know what you're doing, all of this stuff affects the read to the computer and can make the tranny do unexpected things. There are no 'beefed up' parts in a Lightning 4R100, every part in it comes in another model of the transmission except the accumulator, which amounts to a Lightning tranny having a factory installed shift kit. Of all the different assemblies (valve bodies, clutch packs, OD assemblies etc...) in a given model, for the most part the Lightning will get the "big" one, but I wouldn't say that this or that model of most of them are beefier, just different. I will agree that the 6 bolt converter is a comfort, though.

Before you go swapping parts, know this, there are 30 models (for '00 model year) of 4R100 and every one of them was designed for a purpose, for my part I trust the engineers who spent x Million dollars to build all these different models, it costs a lot of money to have so much build complexity and I figure they must do it for a good reason.


BTW,
I'll go tyhwap someone on the head about that snap ring, I hate it when we get something wrong, whatever you may hear about UAW members being dumb and lazy, we really care about quality, it's our only job security.

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'00 Lightning
Manufacturing Tech at Sharonville Transmission Plant