Changing gears in '87 Vert

[Jeb]

I've got a stock 87 with an automatic trans and 2:73 gears. Roughly 100K on the meter.

I've been toying with the idea of changing the gear ratio to give the car a little more ooompf off the line. I'm not too worried about top end since I don't go there anyway but I'd like to improve the acceleration somewhat.

Anyone have any suggestions as to what ratio I should go to and, hopefully, an estimate of the cost to do so? I don't race the car...only normal daily driver type operation.

 

[vetteboy86]

That is something I too have been thinking about. I am not sure what ring and pinion sets they have for the D36. Although any improvement would be worth it.

 

[c4cruiser]

Even going to 3.07's will be a marked improvement. The auto tranny cars got a Dana D36 so you may be limited to the ratio but you should be able to go to around 3.73 or so. Staying around 3.40 will keep fuel economy reasonble but still provide much more acceleration.

The D36 is not as strong as the D44 that came with manual cars, but you can swap in an entire D44 unit with no problems.

 

[Jeb]

Even going to 3.07's will be a marked improvement. The auto tranny cars got a Dana D36 so you may be limited to the ratio but you should be able to go to around 3.73 or so. Staying around 3.40 will keep fuel economy reasonble but still provide much more acceleration.

The D36 is not as strong as the D44 that came with manual cars, but you can swap in an entire D44 unit with no problems.

Thanks for the information. I was thinking of 3.40. I don't race or otherwise abuse the car so the D35 should handle the extra stress if there is any.

 

[WhalePirot]

I'd advise taking your time on this and get some seat time in cars with ratios you are considering. I did not like my change from 3.07 to 3.73 due to the L83's lack of pull above 4500 rpm. Also, my R.E. specialist eventually found a 3.73 gear set that had 2 (vs 1) teeth in contact; effectively about doubling the torque capablity of the D36.

I wanted a 3.36 but could not find a reasonably-priced unit; now run a 3.55.

Also, a too-large change in the ratio will require more than an exterior gear change for proper speedo readings. I got real tired of having to mentally convert my readout to 'real speed', despite being math adept and thinking it'd not be a big deal. The options were to go inside the tailshaft to (also) change the driving gear for the speedo or buying and installing a pulse converting box (about $100).

 

[bart15]

I went from a 3.07 to a 3.73 in my 84 along with a change from the stock 16" wheels to a set of 18" aftermarket wheels and tires. The change for me has meant virtually no change in my gauges but it has sapped my hwy mpg from high 20's to 20 at best. The performance change has been slight at best too. My x-fire was pretty tired going into the project so it has not given me the performance (off the line) boost I was looking for.

I also put in a 2800 stall converter in too. Funny thing is I am more likely to get rubber going from first to second than I am going from a flat start (no power break) off the line. Of course if she's all heat soaked I can't get either.

All in all I'm not unhappy, b/c if I didn't do the gear swap but did the wheel/tire swap she'd be even more of a dog. But I think if I put the 16's back on her I'd be able to overpower the tires more easily. Something I was kind of looking to do when I made the gear swap.

My overall goal is to pull the plant and put something more powerful in so my mods have been in that vein, but as I sit in the middle of it all, I wish I had the money and time to do all that I want to do.

Bart15