Which rear gear ?

I have a bone stock 300i6 bolted to a 4cyl mustang t5 and 3.73 gears in a 8.8 . Cruisin on the highway at 65 according to my calculations I'm runnin 2500 Rpms little to much in my opinion ! My ? Is which rear gear set up will get me around 2000 rpm or less ? I don't want it to be a slug off the line but the majority of my driving is on the highway since I live in the country . Any help or advice is appreciated ... I may have screwed myself buying the 4cyl t5 because of the od gearing but it was dirt cheap ...

 

try search: project33.com and click on calculator, should help. so, you know what rearend gear ratio you have now is from small metal ID tag attached to rear cover?

 

Yeah my current gears are 3.73 . I've used the calculator and 3.00 looks like what I want , but I was looking for someone with real world experience . Just worried that the truck with those gears will be a big turd around town .

 

3:08 is a fairly common gearset for the 8.8 rear. That should get you close.

What kind of vehicle is this?

 

What is your rear tire size, and what is the code on the metal tag, or sticker, or both, on the transmission? It should read 1352-xxx, with the xxx being three digits, which indicate the production number, which will reveal the gear ratios. Without those numbers, everyone is just guessing.

 

Do you know what the ratio is for 1st gear in that T5? That would help to decide how it feels from a stop.

 

66 f100
The first gear ratio is 3.97 ,the tag on the tranny is 1352-209 which is a 91-92 4cyl ford t5 . The rims on back are 17x11 with a 315/35/17

 

There are T5's with a first gear as low as 4.03 if it is too doggy off the line.

The tires you have spec out to about 26" - pretty short for a truck sure and the sizing is certainly not HAMB friendly, but others can argue out that point. According to my info, your T5 probably has the .79 5th gear, so right now you should be at 2475 RPM at 65 MPH. With a 3.08 would give you 2044. You can also get .68 5th gears which would drop your RPM to 2131 while keeping the 3.73 rear gear.

The other thing to remember it that 300 sixes cam in plenty of trucks with a C6 or a 4 speed with a 1.0 top gear. They had a little taller tire, but they did just fine on the highway turning 2600-2900 RPM all day long for hundreds of thousands of miles. I've said it before and I'll say it again, we have become so used to new cars with huge 5 and 6 speed overdrives cruising at 1700 RPM that we forget that 3000 and more was NOT uncommon up to the 70's and even 80's and motors survived just fine! Many of us used to gear for optimum street and strip compromise so that 60 MPH was 3000, 70 was 3500 etc.

 

The rims aren't hamb friendly but it my truck and I like them . I am use to cruisin at 17-18 hundred Rpms down the highway in my daily , my dad said he thought it was doing just fine with the 3.73's. maybe ill just say screw it and leave it alone I really don't like driving it to fast anyway so I guess it works out ... I've thought about changing the 5th gear cluster out but not sure how hard that would be ?

 

I'm running 3:73 in my T and it's great in town. Winds out on the freeway, but I'm not on the freeway that much. Those 315's are killing you on a truck, but it is your car. If you're willing to make the sacrifice, leave everything alone.

That calculator is spot on and I know I'm doing 60 MPH at 2592 RPM. But 60 MPH comes REAL fast and I like it.

 

Yeah in town it's sweet ! Ill probably just suck it up and drive the shit out of it , I know it's a lot better than the three speed I had .. Thanks for the replys guys greatly appreciated ..