Rear end gearing

[scarecrow]

My 85 GT is in the shop right now getting the 30 year old suspension replaced, but it turns out the driveshaft was extremely loose along with the pinion in the rear axle. The car was shaking violently going over 55 MPH and it has been for the two years I've owned it. I am surprised I haven't died driving it. As it is right now, I have no idea what gearing is in there, but I figured 3.73s would be a good choice. The engine turns 2k RPMs going 55 MPH with the current gearing. I'm looking for a more street car and not so much racing. Is 3.73 a decent gear ratio?

Edit: I have a T-5 as well.

[Walking-Tall]

If there's no clutch slippage, and you have 225-60R15's or something similar, 2000rpm at 55 MPH in 5th gear works out closer to 4.10's in the rear axle.
I'd like to say, at 2000rpm, the engine's pretty much loafing along, and getting pretty much the best gas mileage it can. I'd ignore all the hype about lower rpm's during cruise, because I don't care what anybody says, more LOAD (lower rpm and vacuum) equals more fuel drawn in or injected, period. Low load and high vacuum equals best mileage, always. The only thing you'll end up with if you gear down is a lazier low and mid range coupled with less fuel mileage. Just my opinion.

[rob342]

I don't care what anybody says, more LOAD equals more fuel drawn in or injected, period. Low load and high vacuum equals best mileage, always.

i'd agree with that. i'm at 24.75mpg supercharged limping along at 80 with my 4.10. For me the only thing a 3.73 did was make me want a 4.10.

[scarecrow]

I had the clutch and flywheel replaced last October. The shop it is at now said the transmission is solid. Thanks for the info, hopefully the 3.73 gear will make this car a little bit more street worthy. 2k RPMs at 55 MPH is ridiculous with the straights/glass pack set up that is currently on the car.

Edit: Not so much worried about gas.. I have my Civic Si when I'm feeling broke.

[86foxvert]

Three of my cars have 3.73 gears and Im happy with them on the street. Best/first mod to make for the investment (IMO) My sons 86 TTOP has stock gears, not sure yet, but it has great top end. Its stock as they come .....

[Walking-Tall]

I had the clutch and flywheel replaced last October. The shop it is at now said the transmission is solid. Thanks for the info, hopefully the 3.73 gear will make this car a little bit more street worthy. 2k RPMs at 55 MPH is ridiculous with the straights/glass pack set up that is currently on the car.

Edit: Not so much worried about gas.. I have my Civic Si when I'm feeling broke.

Years ago, I put a '72 Mustang 302 and FMX transmission (3 speed, no overdrive) into my '80 Capri RS Turbo, because there wasn't a turbo charger in it anymore and the 2.3 developed a rod or wrist pin knock, and with it's full dual exhaust with straight Thrush mufflers, it was an easy 2500 at 50mph with a nice exhaust burble and with it's original 3.45:1 rear gears, and it was very good on gas, and had nice spirited manners at low speed. With your 3.35:1 1st gear in the T5, it must really haul good. Changing from 4.10's to 3.73's will put you at 1700-1800 rpm at 55 MPH in 5th gear.

I guess I'm not understanding what your question is. Is the exhaust drone in the car on the highway annoying?

[Walking-Tall]

Three of my cars have 3.73 gears and Im happy with them on the street. Best/first mod to make for the investment (IMO) My sons 86 TTOP has stock gears, not sure yet, but it has great top end. Its stock as they come .....

Agreed, gearing makes a huge difference. 3.73's into my 5.0L AOD '86 T-Bird, originally 2.73-geared, made a night and day difference with it all around.

[FUKAZ28]

If you really want it to be smooth put the aluminum FMS driveshaft while you're at it. It's high but you
wont regret it at all.

[scarecrow]

Years ago, I put a '72 Mustang 302 and FMX transmission (3 speed, no overdrive) into my '80 Capri RS Turbo, because there wasn't a turbo charger in it anymore and the 2.3 developed a rod or wrist pin knock, and with it's full dual exhaust with straight Thrush mufflers, it was an easy 2500 at 50mph with a nice exhaust burble and with it's original 3.45:1 rear gears, and it was very good on gas, and had nice spirited manners at low speed. With your 3.35:1 1st gear in the T5, it must really haul good. Changing from 4.10's to 3.73's will put you at 1700-1800 rpm at 55 MPH in 5th gear.

I guess I'm not understanding what your question is. Is the exhaust drone in the car on the highway annoying?

Yes. It's the noise of the exhaust being louder than my awful front speakers lol.

Edit: if my regular drive shaft cannot be balanced then I will go with the aluminum one. Oh and it's really not that loud with the windows up, but I don't have A/C currently though so I always have the t tops off.