[Reinman]

I need to change the ring and pinion in my 85, currently 3.07. I'm thinking of going to a 3.54. I've been told (and read) that the 3.54 would be sufficient vs. the 3.73. I only drive it as a daily driver and want to retain as much MPG's but still add a wee bit of kick. Will I need to recalibrate anything due to the different ratio so the speedo reads accurately or will it be OK on its own? Or should I just stick with the 3.07.

 

[intimid8r3]

if you do the swap you will have to recalibrate some things so it reads right i think you have to reprogram the computer but i dont think its to hard. Im sure someone else will chime in soon with some more help. good luck:thumbsup:

 

[Coolblue65]

You don't have to reprogram, you just need to change the speedo gear/gears in the trans.

 

[War Machine]

You'll love the 3.54 Reinman. artyon:

I had it in the 87. Going from a 2.59 to 3.54 and some other mods that gave me a few more ponies I only lost 4 mpg. I was never able to get a definitive answer as to which tranny gears to changeso I just bought a box that I had to set dip switches on to correct the speedo. I can't even remember the unit I bought, hope someone can chime in w/ the exact gears to buy for the tranny. In the mean time, I'll try to get a name for that unit in case you need it.

 

[GRIPPER]

The speedo drive gears are available at Corvette Central, around $8 each for all gear ratios you mentioned except 3.73.

 

[Reinman]

Rear gear change Recalibrate?

After checking around for a replacement 3.07, it seem the only place to get that gear ratio for the Dana 36 is from a dealer and they want between $525 and $700 just for the gear. I can get the 3.54 or 3.73 AND master rebuild kit for that amount or less so I guess I'll go that route. From the "forums" past experiences, where is the best place to purchase these? Any good or bad experiences to watch out for? Also will I do better with the 3.54 or 3.73 as I really only use the car for daily driving for mpg's? Still would like to know what is involved when recalibtating to compensate for the change in ratio.

Thanks for the help all

 

[Coolblue65]

Again, you don't have to recalibrate anything, you just need to install the correct speedo drive gear and/or speed drivin gear along with the correct vehicle speed sensor. But that all depends on what gear ratio you pick - so see chart link below.

http://www.corvetteforum.net/c4/vettenuts//SpeedometerGearshtm.shtml

or

http://webpages.charter.net/khasting/util/script.html?http://webpages.charter.net/khasting/techinfo/speedocalc.html

If you only have to replace the 'driven' gear and speed sensor, its real easy and involves removing one small bolt pulling out the sensor and gear and replacing- its located on the driver side of the tail shaft. Can be done in 5 minutes and you won't lose any fluid. If you have to replace the 'drive' gear its a little more work as you have to drop the driveshaft and remove the tail shaft housing as well.

I went from a 2.59 to the 3.07's and it made a noticable seat of the pants difference (not extreme but noticable). I picked mine up used, keep a look out for them on ebay, and the classifieds.

 

[Reinman]

gear change recalibrate?

Thanks, Coolblue 65, you pointed out several good ideas. However the best one was that with all the education I have, I really need to pay more attention to the READING part. Sometimes I just get ahead of myself.......

For what I want to do I'll probably stick with the 3.54.

Thanks