Author Topic: Diff gearing (Read 11165 times)

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.

johnny86convert · « **Reply #1 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 ;);););)

onya · « **Reply #2 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:);)

Vette Obsessed · « **Reply #3 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.

onya · « **Reply #4 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

johnny86convert · « **Reply #5 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

69 DIRTY RAT · « **Reply #6 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.

onya · « **Reply #7 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

77CVT · « **Reply #8 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?

johnny86convert · « **Reply #9 on:** June 08, 2004, 09:42:03 PM »

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

Vette Obsessed · « **Reply #10 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...

johnny86convert · « **Reply #11 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.

77CVT · « **Reply #12 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)

Brutus · « **Reply #13 on:** June 11, 2004, 05:13:43 PM »

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

Vette Obsessed · « **Reply #14 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