TTop Tony

I found a retired mechanic who said he'd rebuild my rearend with taller gears for a tad over cost if I pull the pumpkin myself. Well to make a short story long I can't decide between 3.55 or 3.73 gears. I was thinking since I had a 2.64 first gear in my car the 3.5's would be a better choice but a friend of mine said he had 3.73 on his 67 and they really felt great. Unforunatly the closest 1/4 mile track is in Bowling Green 60 miles away so some interstate traveling is required but not much as its not a daily driver. Anybody have any advice. Anybody with a t10 4 speed do the conversion? As always all comments are welcomed.

Never Finished

I don't think you'll notice much difference in the two ratios. The 3.73's will give you a little more torque multiplication. At 80 mph and the transmission in a 1:1 gear, the 3.55's will spin the motor around 3500 rpm's and the 3.73's will be around 3700 rpm's. I'd go with whatever is the least expensive, or if the same cost do the 3.73's. Most magazine articles place the ideal 1st gear overall ratio at 10. 3.73 x 2.64 = 9.84. Another rule of thumb is unless you are going to go at least a .5 change in gear ratio, it is not worth it.

TTop Tony

Funny I calculated 3250@70 with 3.73 but it might have been wishfull thinking. If theres really not much difference then its a no brainer really. I have 3.08's now so I should be able to feel the difference with either of them

Bob Turner

TTop Tony,

Are you going with Richmond gears? I am looking to build a set of 3.70's but if you use Richmond gears I thought you had to change the "carrier" to one that holds 4.11 and up?????

I guess the question is: "Can you install a set of Richmond 3.55's or 3.70s DIRECTLY where the 3.08's are??"

I would suggest finding out on that so you can elimnate any headaches! Hopefully someone on the forum knows.....

Bob :cool:

TTop Tony

I don't know what gears he is using I haven't go that far. He gets his parts at a discount so he's doing all the buying. But I read somewhere that the carrier is the same for the 3.08, 3.5 and 3.7. I'll see if I can dig that up again.

Les

For what it's worth I've heard a number of shops recommend staying with GM gears- they say that the Richmonds are too noisy.

Alwyn678

Yes you can

I put in Richmond 3:73's and I love them.... Launches very nice :reddevil ....I also opted for a 2400 stall and a Transgo shift improver kit which allows it to all work together....By the way they are not any nosier at all. Dont forget the tranny cooler :cheers:


[Modified by Alwyn678, 3:30 PM 3/19/2003]

TTop Tony

Thanks Alwyn678 good to hear from someone who has done the swap.

TTop Tony

I've heard they are noisier too but I've also heard that the reason they are that way is that they are cut straighter which makes them stronger. I guess there is always a trade off.

PatsLs1vette

ive installed richmonds 3.70 in my 3.08 rear and no noise at all.Ive had 3.90's before and no problems.

Glensgages

TTop, you may wanna consider this fact. The Z28s built from '77-'80 with the T-10 4-speed came equipped w/ 3.73 gears from the factory, so, they shouldn't be 'too' much for street/highway driving. While mine is an auto, my best friend's '78 4-spd Z28 (he still owns HIS Z, too), and I believe he turned 2500 RPM @ 55 MPH, with 225/70R15 Goodyears.....

TTop Tony

I did not know that. I guess the gas crunch was over by then. The more I think of it the more I'm leaning toward the 3.73's. It should be a blast.

Bob Turner

Alwyn678,

Thank you for the information!!!!!! I appreciate it!!

Bob
:cheers:

Alwyn678

:cheers:

Jvette73

You can go as high as 3.90 with Richmonds in a 3 series carrier. I switched from 3.08 to 3.90 using the same carrier. With the 2004R in 4th gear with convertor locked I tach 2250rpm @65mph. Not bad for a 3.90 with 26" tires.