Advice? 5.3/th350 273 gears?

[bloodybigblock]

So it's been awhile since I've looked at anything lsx related. I was pretty up to date on knowledge before I deployed so I'm a little rusty now so I need some help/advice. I just purchased another square body and it is a 305/th350 with 273 gears. If I switch to a 5.3 or a 4.8 and use the stock th350 trans and gears will I be okay? Will I have less complications with drive by cable vs dbw? This truck will not be a daily driver and I really don't want to put lower gears and get a 4l60e trans because #1 I don't wanna spend the money and #2 They aren't near as bullet proof as a th350 or th400. I was also going to use the dirty dingo mounts since they seem to be a lot of people's favorites, unless a new style mount came out that's better or a mount where you can keep the a/c in the stock position. So what should I do. I'm not on a budget but this is only a weekend driver and I'm not looking to tear up the streets, just reliability and more power than my weak 305. Thanks

[Clyde65]

Why not do a 4speed auto? with a 4spd, you can run 3.73 or 4.10's. With the 2.73 gears a 3 speed tranny would be fine. what size tires?


I think your mount choice is spot on, pick you up some 1.58"long tubes, probably Doug Thorley, throw a tune and maybe a cam at the 5.3/4.8 and you will have 350-400HP.

AC can be high mount from Kwik performance.

[BR3W CITY]

Originally Posted by bloodybigblock

I don't wanna spend the money

I'm not on a budget

lol so your just cheap?
The 3spd trans has worked plenty of times behind ls motors, but the percieved difference in strength is misleading. The th400 doesn't offer any real advantage over the 4l80e's anymore, since there are now full manual and reverse manual valve bodies for the 80e, and in terms of strength the 80 will take anything the 400 could.

Behind a mostly stock 5.3, the 60e will work and operate fine, it just won't be a bulletproof racing trans....but it sounds like thats not really what you need anyway. That and the cost of a new convertor for the 350 costs about the same as just picking up another 4l60e.

In a heavy vehicle, I would rather run a stock motor with good trans and gears (still have plenty of power, but the gears and trans let you cruise more efficiently, and a steeper rear gear will give you the accelleration you'd be chasing with engine mods)

[bloodybigblock]

Yes i'm cheap. Why would I replace the motor/trans/and rear gears on something I don't plan on driving every weekend and only in nice weather? Like I stated in the 1st post, I want reliability and by "more power" I don't many any mods. That's why I said I wasn't going to tear up the streets. So engine mods are out of the question. My 273 gears feel sluggish but im sure a 305 rated at 150hp/240tq has something to do with that. It'd make sense that a 255hp/285tq dbc 4.8(+tune) would get up to gear faster and I could cruise easily. I run a 28" tall tire. And thank you for the info on kwik performance!

[BigDan3131]

A tall tire, a th350 and 2.73 gears...why bother running an LS engine at all, even with the tiny amount more power you will work that motor to death just like the 305. I would just put a very near stock BBC in it instead and it will make all the torque you need to move and with a little carb it would just fine.

[bloodybigblock]

Ls engines are reliable and that's why I want one. The mpg would also be a little better(especially against a bbc) Didn't much figure I'd work an ls engine to death since they seem to last from my experiences with them. I also don't know how I'd run an engine to death since I stated I'd drive it only on the weekends in nice weather. Thanks for your input.

[softballnrd27]

I drove mine with the exact same setup as you are talking about for about a month before I moved to Japan. I can tell you that it wasn't all that great with the 2.73 gears, i would swap out the gears for 3.42s or 3.73s. You will enjoy the weekend drives more with a little steeper gear, just speaking from my personal experience.

[Zane M]

Your truck will possibly "feel" better with the LS, but it is still going to "feel" sluggish with the 2.73s.

But I understand what you want to do, and why. Good luck with the project.

[Blackpony]

I would recommend going with a 60 and set of 3.73 gears. It will make the truck a ton more fun to drive. If you get 1" setback plates then the th350 will bolt back in at the stock location, you can reuse the stock drive shaft, the shifter linkage will stay the same etc. it will still be a ton faster and more fun to drive with the ls just will leave a little to be desired without gears. I just went through this exact same situation with my truck. I ended up with a built 60 and 3.73 gears. Mileage stayed the same but the fun factor went through the roof!! Haha
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[68GMCCustom]

sounds like you have a plan. I ran my LSx carb'd using an MSD box with the coil on plug setup with a 200-4r in place of the 383sbc/t350 combo I had for a while. Then got an offer for all the efi stuff I couldn't refuse...and thus its efi now with a big 4L85e to replace my 200-4r.

Keep in mind that part of the better fuel economy of LSx motors has to do with having a OD transmission and low cruise rpms. That said...your 273 gears should keep your rpms's down on the freeways...as low as an OD I couldn't say.