Would a 98LC get better gas milage by changing to a A750F transmission (1 Viewer)

[ScottyD]

I have a 98LC but wondered if switching from the stock 4 speed to a 5 speed A750F transmission would improve my gas mileage and could it be done fairly easy?

 

[bamabrock]

Yes. No.

 

[BJJCruiser]

I think the improvement on gas mileage would be offset by the cost and difficulty of the swap. No cruiser gets good gas mileage. It's just a part of the ownership, in my opinion.

 

[camino70]

There may be a fraction of an improvement. Trucks with the five speed have different differential ratios too.

From hoser:

A343F "4-sp Auto" (Effective Ratio=Gear X Diff gear)
- 1st Gear 2.804 (12.06)
- 2nd Gear 1.531 (6.58)
- 3rd Gear 1.000 (4.3)
- 4th Gear 0.753 (3.24)
- Reverse 2.393 (10.29)
Diff Ratio 4.3

A750F "5-sp Auto" (Effective Ratio)
- 1st Gear 3.520 (14.43)
- 2nd Gear 2.042 (8.372)
- 3rd Gear 1.40 (5.74)
- 4th Gear 1.00 (4.1)
- 5th Gear 0.716 (2.936)
- Reverse Gear 3.244 (13.3)
Diff Ratio 4.1

 

[cmck]

I read somewhere the 5 speed had a separate ECU where the 4 speed (my 99) is run into the engine ECU. I would love to see somebody figure it out. I’m interested more for the lower 1st and closer ratios though out. I would only do a swap if mine blew up.

 

[geanes]

I think the improvement on gas mileage would be offset by the cost and difficulty of the swap. No cruiser gets good gas mileage. It's just a part of the ownership, in my opinion.

^^^Yup^^^ The sooner one stops worrying about mpg with these rigs, the happier one becomes. These things ain't Priuses (is that a word?). Heard it once before and like this best: think of "smiles per gallon" I don't care that I get 12mpg. The smile on my face and the joy I have when driving my rig offsets the abysmal fuel economy. Also, it is fun to piss off the environmentalists who hate my rig. Seriously, the carbon footprint my 20 year old rig has is a fraction of what new hybrids have considering the damage to the environment that their batteries alone create (mining, production, replacement, disposal, etc. + the manufacturing of the actual vehicle). The longer a vehicle stays on the road, the less the impact on the environment...unless you're draining your oil into an aquifer. Funny, but true....our rigs are more environmentally responsible than new hybrids