Looking to swap in an overdrive tranny, need advice & opinions

[cobra_4]

I've wore the search out today but I still can't really find the information I need so I'm just going to ask, even though I imagine it has been asked before. Some things have came up that calls for the need of a semi-daily driver with more than two doors so its time to steer my '89 2500 dually suburban more towards a daily driver. With 3.73 gears, no overdrive and a 454 under the hood gas mileage isn't its strong suit. 10-12 is about it.

So I'm thinking/wondering, if I go with an overdrive tranny, will it help the mileage? I'd like to go modern and do a 4l60e/4l80e, not sure what the advantages to either or are, or I could do a 700R4.

Any advice recommendations? Is there a drive shaft that will work or will I have to have one custom made? I assume the 4l's are longer correct? Any other issues I'm going to run into?

Also what about a shifter? Its on the column now, I'd love to retain that but I might could work a lokar floor shifter or something around my center console.

[68Timber]

I've never owned a big block truck, but seems like a lot of guys say 454's do 10 to 12 loaded or empty, overdrive or not. With 3.73's, I'd want an overdrive too. It can only help. And I'd go 4L80E before I'd try a built 700R4, there's really no reason to go there anymore. JMHO, but that's what I'd do.

[cobra_4]

Originally Posted by BRUISER

I've never owned a big block truck, but seems like a lot of guys say 454's do 10 to 12 loaded or empty, overdrive or not. With 3.73's, I'd want an overdrive too. It can only help. And I'd go 4L80E before I'd try a built 700R4, there's really no reason to go there anymore. JMHO, but that's what I'd do.

Thanks for the reply! Yeah, that is what Im afraid of, and that's about what mine gets, 10-12. But it feels like anything over 55 and the motor is screaming(no factory tach, so I'm not 100% sure of the RPM). I don't want to spend the money for the overdrive, if it doesn't really help the mpg. I know it will help the longevity of the engine, but if I can't afford to drive it, it will never get miles put on it anyway

[Irish1941]

Why not look for a GearVendors OD? With 454 I assume is a 2wd.
Pretty simple to install and can be used found for around $3-400. They're tough as nails too.

http://www.superchevy.com/technical/...411sc_od_copy/

[68Timber]

I didn't think you could find one that cheap anymore? They are slick and hell for stout, though.

[95 S_Trucker]

This is a completely different body style/fuel setup, but my 99 ccsb with a 454 gets 10-11. That's it. And it has a 4L80E and 3.73 gears.

But at 70 on the highway, I am at 2000 RPM

[cobra_4]

Originally Posted by 95 S_Trucker

This is a completely different body style/fuel setup, but my 99 ccsb with a 454 gets 10-11. That's it. And it has a 4L80E and 3.73 gears.

But at 70 on the highway, I am at 2000 RPM

That's what Im starting to worry about, if anything I'd imagine yours should get better mileage with the more advance fuel injection on it.

My dad actually has a gear vendors overdrive in the shop that he bought years ago for his 454 SS truck but IIRC someone looked at it ten years ago and said it was missing parts for the install, I'd almost be afraid to tackle that road not knowing everything was there.

[GRADYS Performance]

Depends on your budget and what kind of heavy duty use you use the vehicle for. The 700R4/4L60 is a pretty easy swap with no computer, but not good for towing/HD use. 4L80E is more expesive to do because it requires a computer to run the transmission, But good for towing/HD use. Both should help the mileage with a rpm drop of 25-30% and a lockup converter which helps another 5% at highway speeds.