n00b gear questions

[1990LTD]

The most speed my car sees regularly is 100kph so I'm thinking bigger (numerically) gears might be in order..just after the car shifts to OD (60kph), it's the mushiest slowest shit ever because it drops to like 1100 or 1200 revs


Would the gears keep my engine in a more useful range? The majority of my cruising takes place between 60-80kph and it takes forever to accelerate unless I nail it and it kicks down to 3rd



What maths are involved in determining road speed by rpm/gear and all of that fun stuff?

[Glen]

That's the low end of the power band. 3.07 / 3.27 gears or more if ya like, will help a lot.

[85crownHPP]

Slap the HO upperstuff on there early and see if that helps. My 85 definitely accelerates in OD better than the 91... I rarely have to 'help' it with the gas when the cruise control is on.

[1990LTD]

what gears are in those boxes pete? i have the 3.08 granny gears in mine now....FOR now hehe

[1980c10]

Btw I think od is only a 600rpm drop. Get some h.o. Stuff first my h.o. Swap was money on the highway at like 75 mph with the 3.08's

[85crownHPP]

3.08 in the 85 and 2.73 in the 91. I guess that will make a little difference too..

[1990LTD]

Btw I think od is only a 600rpm drop. Get some h.o. Stuff first my h.o. Swap was money on the highway at like 75 mph with the 3.08's

I've got everything except the injectors and ECU, but they're on their way to me from 85crownhpp. Gonna do the HO swap before I get different gears...I don't know which will make more of a difference.

[1990LTD]

anyone with 3.55s care to share their experience with those gears on the hwy?

[Freshmeat]

3.55s are a great compromise- I had them in a '89 LTC and it was perfect in my opinion. I don't know what RPM it was turning since I didn't have a tach, but it felt just right. Had plenty of low end around town, but cruising on the highway was no issue whatsoever and still made decent fuel mileage for being an old worn out POS.

[1990LTD]

I'm told 3.27s aren't enough of a difference to warrant it so 3.55s seem like the next obvious choice.


Am I right in thinking that bigger (numerically) gears will keep me closer to the powerband at all times? Typical cruising speed is roundabout 80-100kph and the RPMs dont seem like they'll be too high, if my maths are right.

[1990LTD]

also: is the only thing I need to know is if it's 28 spline or not? on both the ring/pinion and the....whatever the fuck it's actually called. i just call it a track lock unit but there's probably a real name for it.

[sly]

basically yeah. know the gears and the splines on the axles/pinion gear. I think for swapping out the rin/pinion, you only need to worry about spines on the pinion. The locker would need to know the axle splines.

[1990LTD]

and 28 is the magic number?

[chitownvic]

I have done the AOD Shuffle and have blown out the OD and some other carnage on a gasket somewhere I can't remember

[1980c10]

yes are cars use 28 spline axles. With 3.73 gears you will only be turning 1900rpm at 100kph, which is damn fine imo. With 3.55's you will turn 1800rpm at 1000 kph. I think I would turn the 100rpm extra and go with the 3.73's and get a little better acceleration.
You will notice a difference in acceleration between 3.55's and 3.73's, But you will not notice a difference in milage between the two.

So I say 3.73's