Overdrive yay or nay

[CM Fab Man]

Hi everyone, I'm in the process of building a modified mini truck and am in the planning process of the good old tall ring and pinion or horsepower and overdrive debate. I have well built 4L80E but still with a 0.75 fourth gear. I'm trying to understand if it really frowned upon to use that overdrive option to get the mile per hour up?

[tortoise]

Might work, depends on the combination. Do the math.

[Stainless1]

There's no rule against it.... but the question is what is the jump for third, how many rpm drop for your combo, will your motor pull and accelerate your vehicle quickly enough to make the speed you need...
Like most will tell ya... build what you think will work, bring it to Bonneville, run it... make changes as required for the next 10 years 
 

[tortoise]

If you can pull to a bit below your target speed in overdrive, the lockup can act like a real close 5th.

[kiwi belly tank]

It will cost you HP to pull an O/D gear in the trans. In a vehicle with enclosed wheels it is better to run the tallest tire you can get under it with 1 to 1 in the trans & the appropriate rear gear ratio to get the speed you're looking for. The only time to run an overdrive in the trans is when you've run out of rear tire options & have the highest ratio you can get.
  Sid.

[Stainless1]

Everything you do to go fast costs HP.... including going fast.... some differentials are more efficient than others.... some transmissions are more efficient than others.... some overdrives.... well you get the point... Aero is the same situation... all you can do is optimize everything within the rules and compromise on the things you have to.... do all you can in preparation and bring all the HP you can afford... go to Bonneville and see if it works....
That is what LSR is.... your idea, your plan, your execution, your race and hopefully your record.
Not everyone gets it...
The attempt and first pass down the salt should be your initial goal... many that start the quest never get that far
After that you work your way up in speed till you get to go as fast as you can... with your idea, that you built and raced... sure everyone wants a record, a small percentage get one 
Even when you get the record... you will want to go faster 

[manta22]

Everything you do to go fast costs HP.... including going fast.... some differentials are more efficient than others.... some transmissions are more efficient than others.... some overdrives.... well you get the point... Aero is the same situation... all you can do is optimize everything within the rules and compromise on the things you have to.... do all you can in preparation and bring all the HP you can afford... go to Bonneville and see if it works....
That is what LSR is.... your idea, your plan, your execution, your race and hopefully your record.
Not everyone gets it...
The attempt and first pass down the salt should be your initial goal... many that start the quest never get that far
After that you work your way up in speed till you get to go as fast as you can... with your idea, that you built and raced... sure everyone wants a record, a small percentage get one 
Even when you get the record... you will want to go faster 

Very well said, Bob.

[bob]

wow , well said . that is exactly what I have learned and the most enjoyable  part about this salt thing.

[CM Fab Man]

Very helpful guys! I will mechanically try and make the target MPH with a 1:1 ratio, and then throw the boost at it and see what happens!

Running C/BFMMP... Hopefully this year! truck will be 1984 Nissan extended cab, LS based with TT's.

[fissionspeed]

Lots of BFMMPs in the works

start a build thread so I can cheat off you lol