Pontiac Grand Prix Forums : Grandprix
 

Grand Prix Forums is the premier Pontiac Forum on the internet. Registered Users do not see the above ads. Please Register - It's Free!

Pontiac Grand Prix Forum - Welcome Register today! Contact us!

Results 1 to 12 of 12
  1. #1
    SE Level Member
    Join Date
    Oct 2015
    Location
    Toronto
    Posts
    44
    Chats
    0

    Default Gearing change w/o tune

    I have been reading through past posts on gear changes but have not found an answer.

    I am racing a 2004 Grand Prix on a 1/3 mile dirt track. The rpm through a race seems low never exceeding 4800. The easy option is to try small diameter tires with a reduced contact patch. The other option being a gear and differential change.

    The race is run in second gear there is no shifting. Can a gear/differential change run well without a tune in this application?

    Cheers Jim

  2. #2
    GrandPrix Junkie SgtMarshal's Avatar
    Join Date
    Feb 2012
    Location
    Kemmerer, Wyoming
    Posts
    4,172
    Chats
    31861

    Default Re: Gearing change w/o tune

    i'm not sure how well it would do, but if you have HP Tuners, you can tell the transmission to only drive in the specified gear, and that might be handy in this situation.

  3. #3
    Killa Bee Scottydoggs's Avatar
    Join Date
    Aug 2010
    Location
    new jersey
    Posts
    37,745
    Chats
    157308

    Default Re: Gearing change w/o tune

    you cant run in just second unless you have a way to command the tranny to stay in second gear. aka 2 nd gear start off the line.

    your not changing gears with out a pcm tune for them.

    and a 1/3 if a mile is 500 foot longer then a 1/4 mile. my last track runs i shifted into 3 rd at the finish line at 97 mph, that was a 6000 rpm shift, way higher then stock. stock is like 80 mph it will shift into 3 rd.

    so how your rpm's seem low is kinda odd sounding.

    if you do start off in 2 manually, it will start in first, shift to second, and stay in second gear. but you'll blow it up like that trying to go a 1/3 mile wot.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  4. #4
    I live here. stealthee's Avatar
    Join Date
    Mar 2011
    Location
    SWPA
    Posts
    8,813
    Chats
    33

    Default Re: Gearing change w/o tune

    Hes not going to hit 97 on a dirt track. He'll be able to stay wide open for the short straights, then have to get out of it in the curves, then back in it. Tops, I bet he hits is 45 mph.
    2011 Mitsubishi Lancer GTS - Stock DD mode
    1994 Dodge Stealth - Currently being revived. Modded

  5. #5
    Killa Bee Scottydoggs's Avatar
    Join Date
    Aug 2010
    Location
    new jersey
    Posts
    37,745
    Chats
    157308

    Default Re: Gearing change w/o tune

    wow i missed the whole dirt track part lol

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  6. #6
    SE Level Member
    Join Date
    Oct 2015
    Location
    Toronto
    Posts
    44
    Chats
    0

    Default Re: Gearing change w/o tune

    Thanks for the replys, HP Tuner would be the way to go, I can't swing that until much later this season.

    Yes it's dirt tracks, so some braking before returning to wot. The transmission is manually set to second gear with a rolling start.

    The videos I have show the rpm on the dash never reaching 5000, maybe 47-4800 regardless of the track conditions. My quick math would put the 3.69 final drive at 6000 if it could hit 5000 in stock trim.

    This could be a better rpm range with some over rev but I didn't know if this is possible without the tune. Should the revs end up too high a change to taller tires would help.

    So this change shouldn't create a safe mode or induce a rev limiter but shifting will be horrible.

  7. #7
    Killa Bee Scottydoggs's Avatar
    Join Date
    Aug 2010
    Location
    new jersey
    Posts
    37,745
    Chats
    157308

    Default Re: Gearing change w/o tune

    smaller tires will get the rpms higher and make it feel snappier, not sure if they would net more speed tho.

    stock engine has no power past the 5500 rpm's either. it just flat lines really.

    are you supercharged or na?

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, 2.8, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW

  8. #8
    GrandPrix Junkie SgtMarshal's Avatar
    Join Date
    Feb 2012
    Location
    Kemmerer, Wyoming
    Posts
    4,172
    Chats
    31861

    Default Re: Gearing change w/o tune

    if you can get a set of 15" wheels, then you can get the good dirt track slick's, but i'm not sure how wide you could go. my inlaws do dirt track racing with modified's, there is a lot of science behind it. it actually might be beneficial to run a 15" wheel and tire on the passenger side and a 16" wheel and tire on the driver because of the angle of the track. another thing you might try is to put lowering springs on the passenger side. I'm sure you understand all the theory behind having different geometry for the dirt track.

  9. #9
    GXP Level Member GTPpower's Avatar
    Join Date
    May 2008
    Location
    Schuyler, NE
    Posts
    2,452
    Chats
    262

    Default Re: Gearing change w/o tune

    What gears do you have now? If 3.29's, you can probably switch to 3.69's without a tune. I did this once. It threw an incorrect gear ratio code and shifted goofy. But if you aren't shifting, it shouldn't matter.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  10. #10
    SE Level Member
    Join Date
    Oct 2015
    Location
    Toronto
    Posts
    44
    Chats
    0

    Default Re: Gearing change w/o tune

    The engine is NA, and a 5500 limit would be fine anything higher would allow for over rev into the corner.

    The current diff is a 3.05, I have a 3.29 in the garage this would get me on par with all the 2nd gen motors.

    Current rims are 17" with low profile rubber, not ideal for dirt but not as tall as 225/60/16. I haven't tried 15" rims over the calipers. Rubber has been by chance no by choice, picking it up from are wreckers. There is a claiming rule so there s a real tight budget.

    I am going to start looking at what is needed to swap a differential.

  11. #11
    GXP Level Member GTPpower's Avatar
    Join Date
    May 2008
    Location
    Schuyler, NE
    Posts
    2,452
    Chats
    262

    Default Re: Gearing change w/o tune

    The diff should swap with no issues. You'll just need s few quarts of trans fluid as some will come out when you pull the axle.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  12. #12
    SE Level Member
    Join Date
    Oct 2015
    Location
    Toronto
    Posts
    44
    Chats
    0

    Default Re: Gearing change w/o tune

    Looks like I will going to a 3.69 final drive, waiting to receive the chain and gears.

    I haven't been into a trans before looking for recommends on manuals and video/YouTube as well as links.


    Cheers Jim

Similar Threads

  1. Replies: 33
    Last Post: 11-29-2014, 12:29 PM
  2. 97 gtp wanting to swap 2000gt trans cuz of gearing change
    By 1badarrowhead in forum 1997-2007 4 speed Automatic (4T65E) (4T65E-HD)
    Replies: 5
    Last Post: 11-07-2011, 09:17 AM
  3. Gearing question.
    By Wakeboy1337 in forum 1997-2007 4 speed Automatic (4T65E) (4T65E-HD)
    Replies: 0
    Last Post: 02-10-2011, 11:54 AM
  4. Anyone run 3.05 gearing (Buick)?
    By Lawngoose in forum PCM Tuning
    Replies: 3
    Last Post: 12-16-2009, 12:06 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •