Ford 9" question

[99ss]

Lot of smart guys here with cross experience....
I have a ford 9" and 3.91 or 90 gears and a trutrac or detroit locker...
mechanical posi unit.... I want to drop the gears to 3.55 .... how do I do it?
Do I need to buy a new unit with the correct ratio or is it less money to take it apart and swap them out?

 

[Budnicks]

go to Moser, Currie or Strange websites, lots of information there,lots of new parts available, lots of gear selections... the 9" Ford parts are very prolific & readily available, you can swap the gears pretty cheaply... less that a hole complete 3rd member/pig/pumpkin, but there are a bunch of them out there, several different style differentials/limited slip etc., to be had used too, probably pretty cheap in some cases... as long as it's not a Nodular Iron Case or Race Unit with updated Bearing support... there are a ton of them made... maybe even on Craigslist or E-Scam

 

[Meep-Meep]

9" ratios are typically 3.0; 3.50; 3.89. The good thing about 9" is they are not hard to work on and pretty darn strong. I'd just get the gears and swap them. Of course this requires you to have a nice shop press and tooling to get the bearings of and on. You will also need a dial indicator and a nice set of calipers won't hurt.

 

[99ss]

Sounds like I need to sub this one out..LOL
I think 3.50 with the 6 speed will be fine. It had 3.42 in it from the factory 3.0 with my cam might not be so nice to drive....but would put me close to like 180 mph I'm thinking..LOL

 

[Meep-Meep]

If you were closer I'd say bring it by!

 

[moparstuart]

Sounds like I need to sub this one out..LOL
I think 3.50 with the 6 speed will be fine. It had 3.42 in it from the factory 3.0 with my cam might not be so nice to drive....but would put me close to like 180 mph I'm thinking..LOL

if you have a 6 speed then 3:91 or even 4:10 work great

 

[99ss]

The problem or what I don't like about them is two fold:
1st gear is almost useless.... If I hit the gas to hard it nothing but tire smoke but beyond that it runs out pretty quick and if I want to lope around it in its kind of to fast to putt through a parking lot

2nd: I am at like 1750-1800 rpms at 70 mph and it eats more gas that way. From the factory it would cruise 70 at like 1450 rpms or so.

I have a 457 and plenty of power I don't need gears to multiply the tq..LOL and its plenty quick so I was thinking if I drop them back I can get better traction longer 1st gear and better gas mileage ... LOL
It was just a thought.. not sure I'll do it I'd rather spend the 800 or so on the Roadrunner.

 

[Budnicks]

what is the low gear ratio in the trans ??, what tire diameter ?? what camshaft ?? in your 6 speed, is it a double overdrive trans ?? {meaning 5th & 6th gear are both O/D ratios} if it is, you can possibly go with a steeper/lower final rear end gear ratio & still have great drive-ability & freeway/hwy manners/rpm's {unless you want just top end overall speed, than go with a taller/higher gear ratio}... theres a place with some great calculators for all kinds of stuff ,including gear ratios & tire sizes try www.WallaceRacing.com/Calculator.htm , good luck

 

[99ss]

18 " wheels, 30 series tire. have no clue about the gear ratio and I think 6 is the 1:1 ? 5th pulls to hard Cam is a 247/262 115 + 3

easy info to attain I think.. 99 Camaro SS, I'll do some digging

 

[moparstuart]

17-1800 rpm at 70 or 80 MPH is fantastic , try paying the fuel bill for 3500 to 4000 at 80 mph LOL

 

[Cranky]

A 6 speed with no OD? That sounds pretty strange to me....

 

[99ss]

A 6 speed with no OD? That sounds pretty strange to me....

LOL I have no clue what the ratios are

- - - Updated - - -

Transmission gear ratio (1st) 2.66 Transmission gear ratio (2nd) 1.78 Transmission gear ratio (3rd) 1.30 Transmission gear ratio (4th) 1.00 Transmission gear ratio (5th) .74 Transmission gear ratio (6th) .50 Transmission gear ratio (reverse) 2.90

Not sure if hat is accurate I found them on the internet..LOL cargurus

stuart the 79 z28 was at 3500 rpms at 70..LOL ate gas like no tomorrow and still didn't have power...hahahahaha

 

[moparstuart]

99 camaro would be a tremec T-56 and 6th gear is OD

 

[Budnicks]

18 " wheels, 30 series tire. have no clue about the gear ratio and I think 6 is the 1:1 ? 5th pulls to hard Cam is a 247/262 115 + 3

easy info to attain I think.. 99 Camaro SS, I'll do some digging

I'm pretty sure all the {Tremec T56} GM 6 speeds are an O/D like 0.69%-0.75% {my 25th Annv. 6 spd Firehawk/Trans Am was} 5th gear is probably 1:1... I would have to look it up too, for the actual final drive ratio... maybe just a taller tire would help some, cut the ratio a little, if that's what your after...

 

[MarPar]

including gear ratios & tire sizes try www.WallaceRacing.com/Calculator.htm , good luck

Buds, looks like you haven't updated your bookmarks since the last time we had this discussion!! LOL

here's the site for the calculator(s)!!! member, you had to have the "s" on the end of calculators!!

http://www.wallaceracing.com/Calculators.htm