Swap rear axle ratios

Swap rear axle ratios

Postby guyonearth [OP] » November 29th 2009, 3:39pm

Would there be any bad repercussions if I swapped the 3.73 axle in my 2WD '97 Astro with a 3.53? I know the speedo might be off, but it's already slightly off now.
Original Poster [OP]
guyonearth
Firing on 1 Cylinder (L1)
Firing on 1 Cylinder (L1)
Years of Membership: guyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full years
Posts: 185
Topics: 5
Joined: June 2009
Gender: Male
Alias (AKA): DeanC

  • Similar topics
    Replies
    Views
    Author
  • Put in 2005 axle assembly on a 1999 Van?
    by Silver99 » November 2nd 2020, 3:42am in Rear-End
    8 Replies
    755 Views
    Last post by SainT View the latest post
    November 4th 2020, 9:26pm
  • G80 swap
    by Rockridge » March 14th 2021, 3:31pm in Rear-End
    8 Replies
    248 Views
    Last post by Rockridge View the latest post
    March 15th 2021, 1:15am
  •  
    10
    70
    Last post by AstroSafari.com View the latest post
    April 15th 2021, 1:09am

Re: Swap rear axle ratios

Postby moneymaker » November 29th 2009, 3:47pm

The computer has already been programmed for the original gear ratio, wheel and tire size for the correct shift points in your transmission. You can change all this, but my recomendation is to buy a power programmer and reprogram with the new ratio and wheel and tire size so your shift points won't be off, plus the speedo.
moneymaker
V8 Swap Achievement
V8 Swap Achievement
Firing on 1 Cylinder (L1)
Firing on 1 Cylinder (L1)
Years of Membership: moneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full yearsmoneymaker has been a member for 11 full years
Posts: 186
Topics: 7
Joined: October 2009
Alias (AKA):

Re: Swap rear axle ratios

Postby guyonearth [OP] » November 29th 2009, 4:23pm

Can you recommend which device to get and where to get it?
Original Poster [OP]
guyonearth
Firing on 1 Cylinder (L1)
Firing on 1 Cylinder (L1)
Years of Membership: guyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full years
Posts: 185
Topics: 5
Joined: June 2009
Gender: Male
Alias (AKA): DeanC

Re: Swap rear axle ratios

Postby Gary » November 29th 2009, 4:41pm

The gear ratio I think your talking about is 3.42's and not 3.53....right??.The 3.73's are just about the best all around rear end gear you can get with these vans.Are you sure that you have 3.73's by the RPO code??.The 3.42's are more common in these vans.If you do end up taking them out make sure you list them for sale here if they are in good shape and watch the guys here fight over them. :thumbup:

Yeah-I edited the post to correct the statement of 3.43's to 3.42's.Well a senior moment. :rofl: Ya know ya reach a age when you don't have so many teeth to count in ya head.......so rear end gears get much harder. :shrug: :rofl: :rofl: :wave:
User avatar
Gary
Dearly Departed
Firing on 4 Cylinders (L3)
Firing on 4 Cylinders (L3)
Years of Membership: Gary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full years
Posts: 2472
Topics: 136
Joined: April 2008
Location: Rochester,NY 14559
Gender: Male
Alias (AKA):
Van Make/Model: Chevrolet Astro
Extra Info: high top

Re: Swap rear axle ratios

Postby Gus_Mahn » November 29th 2009, 7:12pm

I doubt you'll notice much of a difference. Acceleration will be slightly slower, and fuel mileage may be slightly better. Cruise rpm should be 200-300 rpm lower at 70 mph.

I deal with Mustangs quite a bit. To those considering a gear swap, I recommend only swapping gears if you're going to swap 2 gear sizes. Ford example 3.08:1 stock gear, next size gear 3.27:1, I'd recommend 3.55:1 as the minimum swap gear. I'dealy I'd recommend 3.73:1 for stick shift and 3.90:1 or 4.11:1 for automatics.

In the case of an Astro, I think 3:42 is close to ideal for those not pulling trailers, but 3.73 is close and pulls trailers better than 3.42's. I believe the next smaller GM gear is 3.31:1. I'm not sure if a stock Vortec will pull this gear in high winds at highway speeds. If this is the case, you may actually lose fuel mileage at highway speeds.
Gus_Mahn
Fueling (7/8 tank)
Fueling (7/8 tank)
Years of Membership: Gus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full yearsGus_Mahn has been a member for 12 full years
Posts: 90
Topics: 10
Joined: January 2009
Alias (AKA):

Re: Swap rear axle ratios

Postby guyonearth [OP] » November 30th 2009, 3:01am

I meant 3.42, I'm not sure what I was thinking. I was hoping for slightly better mpg if possible. The van has tons of power, that's hardly the problem.
Original Poster [OP]
guyonearth
Firing on 1 Cylinder (L1)
Firing on 1 Cylinder (L1)
Years of Membership: guyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full yearsguyonearth has been a member for 11 full years
Posts: 185
Topics: 5
Joined: June 2009
Gender: Male
Alias (AKA): DeanC

Re: Swap rear axle ratios

Postby Gary » November 30th 2009, 8:12am

guyonearth wrote:I meant 3.42, I'm not sure what I was thinking. I was hoping for slightly better mpg if possible. The van has tons of power, that's hardly the problem.


What is the gas mileage??.When was the last tune-up??.Did you use Delco parts??.Last change of fuel filter??.I suggest you need to look at "the big picture" of a gas mileage issue before a radical gear change.And one which might be a move in the wrong direction.
User avatar
Gary
Dearly Departed
Firing on 4 Cylinders (L3)
Firing on 4 Cylinders (L3)
Years of Membership: Gary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full yearsGary has been a member for 12 full years
Posts: 2472
Topics: 136
Joined: April 2008
Location: Rochester,NY 14559
Gender: Male
Alias (AKA):
Van Make/Model: Chevrolet Astro
Extra Info: high top

Re: Swap rear axle ratios

Postby Mr_Bowtie » November 30th 2009, 8:51am

Like what was stated above if you wanna do a gear swap don't both with just one step up or down in gears as that would be pointless. If your going to swap the 3.73s out for some gears with better gas mileage then you might consider go down to 3.23 or even further down to 3.08 gears. I personally think it all comes down to vehicle maintanence and how you drive the vehicle more then just final drive ratio. Buy yourself a vacuum gauge and make yourself stay off the gas pedal and drive 5mph slower. :layrubber:
1985 Astro - 350/700r4....loud & low! :chevy:
'96 Dodge 2500 Ramwagon Van
'68 VW Bug 1600cc
'00 Grand Prix GT
'00 Subaru Outback Legacy sedan
User avatar
Mr_Bowtie
V8 Swap Achievement
V8 Swap Achievement
Firing on 8 Cylinders (L7)
Firing on 8 Cylinders (L7)
Years of Membership: Mr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full yearsMr_Bowtie has been a member for 11 full years
Posts: 7355
Topics: 74
Images: 29
Joined: April 2009
Location: Brownsville, WI
Gender: Male
Alias (AKA): Nick
Van Model Year: 1985
Van Make/Model: Chevrolet Astro
Extra Info: 350 with 700r4

Re: Swap rear axle ratios

Postby 91astroluv » November 30th 2009, 9:58am

Gary wrote:Well a senior moment. :rofl: Ya know ya reach a age when you don't have so many teeth to count in ya head.......so rear end gears get much harder. :shrug: :rofl: :rofl: :wave:


Yeah and I hear when things in your rear start getting harder rather than the thing in the front, That's when you should begin to worrrrry!!! :rolling: :rofl:
91astroluv
Firing on 1 Cylinder (L1)
Firing on 1 Cylinder (L1)
Years of Membership: 91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years91astroluv has been a member for 11 full years
Posts: 167
Topics: 7
Joined: May 2009
Alias (AKA):


 
  • Related topics
    Replies
    Views
    Last post

Return to Rear-End

It is currently April 15th 2021, 1:09am

Rear-End Forum
Rear-EndA differential is a device employing gears capable of transmitting torque and rotation through shafts. Essentially the differential allows each of the driving wheels to rotate at different speeds in the rear axle.
To create a new topic in Rear-End, click this button:
Previous topic Next topic
Recent Image Attachments
Attached by:
Rockridge
in Rear-End
Views: 248
Comments: 8
Date: Mar 14 '21
Time: 4:49pm
» Read last comment
Attached by:
Rockridge
in Rear-End
Views: 248
Comments: 8
Date: Mar 14 '21
Time: 3:20pm
» Read last comment
Attached by:
Attached by: SportsBoy
SportsBoySportsBoy is online!
in Rear-End
Views: 658
Comments: 21
Date: Feb 15 '21
Time: 3:03am
» Read last comment
Attached by:
Attached by: SportsBoy
SportsBoySportsBoy is online!
in Rear-End
Views: 658
Comments: 21
Date: Feb 10 '21
Time: 11:44pm
» Read last comment
Attached by:
Attached by: SportsBoy
SportsBoySportsBoy is online!
in Rear-End
Views: 658
Comments: 21
Date: Feb 08 '21
Time: 3:04pm
» Read last comment
Sponsors

Who is online

Users browsing this forum: No registered users and 2 guests