3:07 diff change
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
3:07 diff change
I am saving up the cash to put a 3:07 diff in the 91. How big of a change will I feel in acceleration switching from the 2:59 to the 3:07? I am hoping it will be a big change. Also how much of a HP change would I get if I put on long tube headers and then went with a true dual exhaust setup with hi-flow cats and an X-pipe set up. I have bullet mufflers on it now. I am going to delete the pre-cats too. I am hoping that it won't make it too loud.
Drifting
Joined: Oct 2004
Posts: 1,976
Likes: 0
From: Patchogue NY
From what I understand, and I'm no expert, you might want to get into a Dana 36 with the 3:54 gears. I have a 91 also, and I'm close to buying one from ZIP for $895, plus a $410 refundable core charge. If your looking for street use with maximum performance the consensus is 3:54. LOL
Joe B.
Joe B.
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
will switching to 3:54's hurt any on the daily driving? We like to cruise alot in the summer and I don't want to kill my fuel mileage. I bet it would be a screamer with the 54's. It is fast now, but I can't imagine what it would run like with those in it. 
Drifting
Joined: Oct 2004
Posts: 1,976
Likes: 0
From: Patchogue NY
You will loose some mpg, but from what I read, it's negiligible. By the way, I'm trying to start a group buy on another thread on the "tech/Perf" track, for the Dana 36 with the 3:54 gears from ZIP. I sent the ZIP rep. a pm, and were looking for other's who would like to get in on this. The thread is called: Dana 36 3:54 gears from ZIP.
Joe B.
Joe B.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by 91redragtop
I am saving up the cash to put a 3:07 diff in the 91. How big of a change will I feel in acceleration switching from the 2:59 to the 3:07? I am hoping it will be a big change.
I think people on here generally say 3.54 is a bit much for the L98 (or maybe they say you shouldn't go bigger than 3.54 with L98, something like that...)
There are lots of 3.07 vettes out there. Find somebody to let you drive his and see if it is enough for you.
Drifting
Joined: Oct 2004
Posts: 1,976
Likes: 0
From: Patchogue NY
Originally Posted by steve9899
There are lots of 3.07 vettes out there. Find somebody to let you drive his and see if it is enough for you.
Joe B.
Pro
Joined: Aug 2001
Posts: 616
Likes: 13
From: Loudon, TN
My 90 has the 3:07 rear and my 93 has the 2:59. Big difference in off the line feel between the two. Even with 50 more HP in the 93 it doesn't feel as strong as the 90. Mileage is not bad with the 3:07 but it won't touch the 2:59. Highway driving in the 93 I get around 25 - 26 mpg but the best I've gotten with the 90 is 22. If you plan on doing a lot of highway crusing I don't think you want anything lower than 3:07. With the 3:07 gears I can smoke the tires so I don't think a lower ratio will do any better because you will lose traction even easier.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by joe3906
I've done my homework regarding the swap from a 2:59 to the Dana 36 3:54, and I'm comfortable with my decision. I apprecite your insight, but for me, it's the 3:54 differential.
Joe B.
Joe B.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
can anyone give me a quesstimate on how much mpg's I would get with 3:54's? I don't want to get down to 13 or 14 mpg's. You did come up with a good point about traction. I can light up the tires and smoke them nonstop with the 2:59's in it so 54's might make it hard to get going. My biggest gripe with my 91 is the rolling punch from say 40 and above. It just doesn't pull like I think that it should. It pulls hard but my 95 Impala SS with just a few minor mods feels like it pulls harder and the vette has more torque. I know that it has 3:08 gears in it, but it weighs a ton(hi-po land barge). That is what I want to improve the most. Maybe it is just me but my 91 doesn't pull that great from dead stop. I have found that starting off and then nailing it at about 10 mph makes it pull strong. It will catch second doing that but won't from a dead start. That is why I am highly considering the 54's, so it will be evil when you nail it. More opinions please. Hopefully someone with 54's will chime in.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by 91redragtop
can anyone give me a quesstimate on how much mpg's I would get with 3:54's?
Then subtract a couple mpg from that because you'll have your foot in it all the time because it's more fun.
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
This is a really hard decision because I want a screamer but don't want to kill being able to drive it all the time. I believe that I would like the 54's much better and if the wife doesn't like that it gets worse MPG's she will just have to get over it. Wait...if I didn't tell her that I changed out the diff and never let her fill up with gas she would never notice. 54's it is. Watch out riceburners and gas stations....here I come.
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
Does anyone have a clue what the RPM range will be when cruising on the interstate(75-80MPH) with 54's installed in a vette as compared to 2:59's? Does anyone on this forum have the 54's installed on their vette? I would like to hear from someone with them installed as to how high in the RPM range it threw their motor after the install.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Love my 3.07's. However, any difference in mileage will be negated by the smile it brings when you stomp on it. If you want more punch from the 40+roll go 3.54. It's worth it
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Originally Posted by 91redragtop
Does anyone have a clue what the RPM range will be when cruising on the interstate(75-80MPH) with 54's installed in a vette as compared to 2:59's? Does anyone on this forum have the 54's installed on their vette? I would like to hear from someone with them installed as to how high in the RPM range it threw their motor after the install.
http://www.f-body.org/gears/
Thread Starter
Burning Brakes
Joined: Sep 2003
Posts: 813
Likes: 1
From: Middle Tn
Calling any or all 3:54 geared L98 owners. Tell me likes, dislikes and what kind of punch your vette has now. Trying to make the crucial decision on 3:07's or 3:54's. Gotta keep the wife happy on MPG's but want to wear out riceburners for kicks. I don't know if any of you read my other post but will someone please tell me how putting an obnoxiously loud muffler on a stock riceburner gives it 10,000HP and makes it able to outrun any car on the road? 
Team Owner
Joined: Dec 2000
Posts: 21,090
Likes: 282
From: Phila., PA burbs
I've had a 2.59, a 3.07 and a 3.33 in my 91. With the 2.59 I was able to get over 30 mpg on a run to the Jersey shore. With 3.07s this trip went to about 27 mpg and finally with the 3.33s its down to about 24-25 mpg. As other have alluded to, L98 Corvettes really don't need a lot of gear. 3.07s are the perfect gear for the L98, in my opinion. To be honest even 2.59s aren't too bad with this motor. I have drag strip data for all three rears I've had in my car and while there was some improvement with each rear change, it wasn't as much as I expected.
Last edited by TA; Dec 22, 2004 at 09:27 PM.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by conv90
I really need to know if something mid between 3.07 and 3.54 like a 3.23 is available for a 2.73 carrier .
I think the only thing between 3.07 and 3.54 for a D36 is a 3.31 from 1984 which is rare, and that would be a 3-series carrier.
If you find one let us know. I'd also like to be around 3.3.
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by conv90
I'm in the same decision but I really need to know if something mid between 3.07 and 3.54 like a 3.23 is available for a 2.73 carrier .
I have a 2.73 and it is so close to the 2.59...
-Beppe-
I have a 2.73 and it is so close to the 2.59...
-Beppe-
This may not be practical for the earlier cars where you have to change the speedo calibration with hardware instead of just programming the computer.
It's also not cheap especially since I have new tires and they should last me 4-5 years at the rate I drive the car...
Safety Car
Joined: Feb 2001
Posts: 4,397
Likes: 0
From: Looks like I picked the wrong week to stop sniffin glue Orlando
Originally Posted by steve9899
I think the only thing between 3.07 and 3.54 for a D36 is a 3.31 from 1984 which is rare, and that would be a 3-series carrier.
If you find one let us know. I'd also like to be around 3.3.
If you find one let us know. I'd also like to be around 3.3.
These peeps have a 3.31.... Was the 84 D36 carrier in some way different from the rest so that this gear would not work for the mass's
