3.73 or 3.90 help
Tech Contributor
Joined: Mar 2003
Posts: 12,094
Likes: 197
From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
here is something for you to compare by.
My 100% stock 2001 TA LS1 with M6 and 3.42 gears got 29 mpg going from KC to California and back.
I put heads/cam/headers/4.56 moser 12 bolt with all of the other BMR goodies. car put out around 430 rwhp on 28" slicks at the dyno. Drove it with street tires from KC to Kentucky and back and still got 24 mpg highway.
After all the engine work and before I put the rear end in (did not do it until I broke the stock rear end at the track) I found a nice road where I hit 188 mph (the trip to california was to go to Granatelli's and get their 200mph speedo for my TA since I was burying it.
After the 4.56's, I found another deserted road where I topped out at around 155mph.
with 4.10's, 4.33's or 4.56's you can actually use 6th gear.
With 3.42's I would go across the 1/4 mile line in the top of 3rd gear
With 4.56's I would go across the 1/4 mile line in the top of 4th gear.
I guess what I am saying is don't be afraid of 4.10's.
My 100% stock 2001 TA LS1 with M6 and 3.42 gears got 29 mpg going from KC to California and back.
I put heads/cam/headers/4.56 moser 12 bolt with all of the other BMR goodies. car put out around 430 rwhp on 28" slicks at the dyno. Drove it with street tires from KC to Kentucky and back and still got 24 mpg highway.
After all the engine work and before I put the rear end in (did not do it until I broke the stock rear end at the track) I found a nice road where I hit 188 mph (the trip to california was to go to Granatelli's and get their 200mph speedo for my TA since I was burying it.
After the 4.56's, I found another deserted road where I topped out at around 155mph.
with 4.10's, 4.33's or 4.56's you can actually use 6th gear.
With 3.42's I would go across the 1/4 mile line in the top of 3rd gear
With 4.56's I would go across the 1/4 mile line in the top of 4th gear.
I guess what I am saying is don't be afraid of 4.10's.
You and JoeG make me feel like the truth of gears is known and demonstrated at the track. I was worried this would be another "gears only feel faster" thread.
A H/C car with 475 to 500rwhp will see .3 ET improvement....and yes it also feels faster.
Tech Contributor
Joined: Mar 2003
Posts: 12,094
Likes: 197
From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
Do yourself a favor and find a tuner that does the swap in house. Prices for built diffs have really gotten out of hand. What ECS or Cartek do for 1700 installed (gears + a hardened output shaft) is now 1800+shipping+install from other sources. You have 120 bucks for shipping and you have to ship back your core; another 120 bucks.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
Do yourself a favor and find a tuner that does the swap in house. Prices for built diffs have really gotten out of hand. What ECS or Cartek do for 1700 installed (gears + a hardened output shaft) is now 1800+shipping+install from other sources. You have 120 bucks for shipping and you have to ship back your core; another 120 bucks.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
You want somebody to stand by their work on this.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
No, it's not bad. But if you have trouble (and it happens, I got a set of 3.90's that evidently wasn't hardened properly and started whining, others who got them at that time also had problems) and you bought the diff and brought it to a shop, they will finger point on whose fault the failure is.
In my case I have a trusted shop and they stand by their work. I did not pay for warranty work, I just got a replacement diff that is still going strong.
If you are going to do it yourself (not bad if you have a lift), then just use a trusted supplier. There are several who are sponsors on this board.
In my case I have a trusted shop and they stand by their work. I did not pay for warranty work, I just got a replacement diff that is still going strong.
If you are going to do it yourself (not bad if you have a lift), then just use a trusted supplier. There are several who are sponsors on this board.
Last edited by Joe_G; Mar 13, 2011 at 08:22 AM.
Team Owner
Joined: Feb 2001
Posts: 27,254
Likes: 136
From: Short Hills, NJ
Do yourself a favor and find a tuner that does the swap in house. Prices for built diffs have really gotten out of hand. What ECS or Cartek do for 1700 installed (gears + a hardened output shaft) is now 1800+shipping+install from other sources. You have 120 bucks for shipping and you have to ship back your core; another 120 bucks.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
A tuner is responsible for the parts and work. If you source a diff and there is a problem, the installer isnt going to take it out and install the replacement for free. If he didnt supply the part, its your problem.
100%
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Melting Slicks
Joined: Nov 2004
Posts: 2,408
Likes: 145
From: Northcentral, Pennsylvania
St. Jude Donor '09-'11
My first set of 4.10's were defective and whined very loudly after a few hundred miles. ECS stood by their work (as always) and replaced them at no additional cost.
