NSW Corvettes

Technical Tips => Transmissions - Differentials => Topic started by: onya on June 03, 2004, 08:52:27 PM

Title: Diff gearing
Post by: onya on June 03, 2004, 08:52:27 PM

I got a 86, 4 speed auto with a ( by the options code) 2.59 diff. Is this good/ bad. I have not been on the freeways yet and don't know what to expect as overall speed. Any ideas.

Title: Diff gearing
Post by: johnny86convert on June 04, 2004, 08:37:54 AM

onya  I  have an  88  with  the  same  diff  and  am  thinking  of  going  to  3.55.Would  certainly  help  that  gap  between  3rd  and  4th.  Have  been  told  I  could  go  to  3.75  but  maybe  a  bit  too  much??.You  have  to  get  the  tranny  recalibrated/speedo  at  the  same  time.Theres a  guy  in  Marrickville  who  has an  88  also  and a  great  mechanic,he'll  be  doing  mine  when  I  finsh  saving  up  for  the  move  to  changing  it.On  the  cruise  to  the  melbourne  convention  4th  geat  in  cruise  control  was  great,humming  along  nicely  but  with a  3.55  you  might  have  500  more  rpm  but  its  only  petrol  LOL  ;);););)

Title: Diff gearing
Post by: onya on June 04, 2004, 08:49:37 PM

Have you had a rough idea of the price to buy and diff and price to install. I spent a bit buying the vette and my wife, well, she not impressed about spending a whole lot more. Funny thing, we went for a small cruise the other night and she asked " I thought we were only going to use the vette on special days" quickly I said " Any time I get to drive the vette is a special day and tonight is one of those times" ;27;28;28;27:);)

Title: Diff gearing
Post by: Vette Obsessed on June 05, 2004, 12:46:10 AM

A 2.59 ratio is good for highway cruising but not so good for acceleration.  With the diff ratio you have the car will definitely be suited to the highway, but it will not accelerate as well a a 3.07-3.73 geared automatic.

I wouldn't suggest changing the gears unless you aren't happy with the performance you have at the moment.  Drive it around for a while and get a feel for it before you start changing things.

Title: Diff gearing
Post by: onya on June 05, 2004, 09:28:13 PM

Wife and I went for a run along M5, I found as I was told there is a big difference between 3rd and 4th, when in the suburbs I mainly stay in third but on the freeway, goes great. I feel my tyres have a small flat but annoying flat spot. Must talk to big brother, and I am not changing anything at the moment just asking a few questions. Thanks;27

Title: Diff gearing
Post by: johnny86convert on June 06, 2004, 10:33:42 AM

ONYA,  HAVE  to  agree  ,round  down  I  keep  mine  in  third,on  the  open  road  fourth  is  great.I  got  quoted  around  4  to 5  grand  to  make  our  C4's  up  and  boogie.Thats  with  diff/tranny/manifold/injection/throttle  body  changes,  but  where  do  you  stop.??We've  even  done  sums  on a  85  sh#t/box  from  the  states  and  doing  the  whole  make  over  paint/interior  with a  500  cube  injected  Mr  Grunt  gutter  slapper  and  you  wouldn,t  get  much  change  out  of  $70  grand  hehehehehehe  ;);):pinki

Title: Diff gearing
Post by: 69 DIRTY RAT on June 07, 2004, 05:04:39 PM

How about puttin in a SHAFIROFF 472 cubic inch (635hp) small block,YES they make them now!.It can easily replace a C4 engine! It has a slightly taller block-but thats all. Only $11,750us.

Title: Diff gearing
Post by: onya on June 07, 2004, 08:32:01 PM

Yeah, There are some part of my body that I still want attached to, even as old as I am. to mention spending MORE money at this point would not go down very well. When I bought the 86 my wife ordered a new kitchen said she would only spend 7 thou, but NO, Peter got a vette now I would a 12 thou kitchen, ALL GONE. ;37;30;30

Title: Diff gearing
Post by: 77CVT on June 08, 2004, 10:31:02 AM

Quote

... to  make  our  C4's  up  and  boogie.....

What do you class as get up and boogie?  13.5's not good enough? (http://www.corvetteforum.cc/zeroimg/smilies/wink.gif)

Title: Diff gearing
Post by: johnny86convert on June 08, 2004, 09:42:03 PM

sorry  77  i'm  thick  whats  13.5????????  mean

Title: Diff gearing
Post by: Vette Obsessed on June 08, 2004, 09:51:43 PM

13.5 ET - as in a 13.5 second quarter mile capability.

I was wondering if it was your car or Chris's that does a 13.5...

Title: Diff gearing
Post by: johnny86convert on June 09, 2004, 08:42:24 AM

VO  I  think  it  was  chris's,  his  vette  was  really  quick  in  melbourne  in  the  garage  events if  its  the  vette  I'm  thinking  of.Mine  is  stock  but  would  like a  bit  more  grunt,BTW  I  am  still  interested  in  the  headers  you  have  for  sale.

Title: Diff gearing
Post by: 77CVT on June 11, 2004, 08:55:55 AM

I would have thought most C4's would do sub 14.5's?????

(mine only does 14.1's)

Title: Diff gearing
Post by: Brutus on June 11, 2004, 05:13:43 PM

And here's me thinking you guys were talking in inches!:22

Title: Diff gearing
Post by: Vette Obsessed on June 11, 2004, 05:19:35 PM

JH, no worries about the headers.

Chris, I think you are right on the money.  From what I have seen firsthand, most stock C4's are good for 14.0 - 14.5 ET's.

I have seen a lightly modded 89 auto run a 13.9 (or was that a 13.8?) with light mods and 3.07 gears on the old Eastern Creek strip (which had a slight uphill section that knocked about one tenth off most production cars from what I understand).  My experience is that each tenth after that starts to cost you more and more money (as expected). ;ay