Rebuild transmission with diff install or naw????
Thread Starter
Heel & Toe
Joined: Oct 2015
Posts: 22
Likes: 0
From: Antelope valley Californai
Rebuild transmission with diff install or naw????
So I have a 3.42 reared for my a4. I originally thought that putting this thing in would be a pain in the *** so my initial thought was to take the car into a trans shop and get the trans rebuilt for peace of mind and just have them throw the new diff on. I got quoted for 1800 including a new higher stall.
Upon further research, it looks to be a prett easy job to replace the diff as the whole sub frame just drops out. I guess my question is should I just go ahead and get the trans re done too? I mean the car runs great and the trans feels super solid. The cars not my daily driver anymore. And I also don't have gobs of money either. I could save for it and do it if necessary, but I'd rather not. Opinions???
Upon further research, it looks to be a prett easy job to replace the diff as the whole sub frame just drops out. I guess my question is should I just go ahead and get the trans re done too? I mean the car runs great and the trans feels super solid. The cars not my daily driver anymore. And I also don't have gobs of money either. I could save for it and do it if necessary, but I'd rather not. Opinions???
Thread Starter
Heel & Toe
Joined: Oct 2015
Posts: 22
Likes: 0
From: Antelope valley Californai
It's got 120k miles. Whole car has been serviced through the dealer. It's been driven frequently. But not hard. Previous 2 owners were enthusiasts who took care of it
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
In my opinion, doing it yourself is the game changer here. You say your transmission is solid, the car has never been tracked and has been cared for and well maintained.
You were going to rebuild the transmission as "preventive maintenance" to avoid having to pay twice for dropping the rear end in case it failed in the future, not because there was a problem. Doing it yourself takes out of the equation the "double expense".
You also said that you rather not spend money unnecessarily, so I think you have your answer right there.
You were going to rebuild the transmission as "preventive maintenance" to avoid having to pay twice for dropping the rear end in case it failed in the future, not because there was a problem. Doing it yourself takes out of the equation the "double expense".
You also said that you rather not spend money unnecessarily, so I think you have your answer right there.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Having over 100K miles on the trans I would deff. do a mild rebuild NOW----Especially if you are doing the stall and the 3.42 gear change----These mods will make your car a beast off the line- If left sock-in return it will be hard on your trans ---Stall converters add heat so don't forget to install a larger aftermarket trans cooler----The added stall will create more TQ multiplication then stock
Lastly---A stock trans tune on a C5 still is programmed for mild soft shifts---This is done by slipping the clutches somewhat-- I would also recc getting a trans tune---This is the best thing you can do to make your trans live---If you decide NOT to rebuild the trans I would at the least get the trans re-tuned to eliminate the soft shifts---Also the stock tune locks the converter very slowly and at a low low 38 MPH----This makes your engine lug --hard on it as well as the trans---A retune will create firm crisp shifts as well as lock up the converter at a better 50-53 MPH and at a much firmer non slipping feel--
all of these things add life---
Lastly---A stock trans tune on a C5 still is programmed for mild soft shifts---This is done by slipping the clutches somewhat-- I would also recc getting a trans tune---This is the best thing you can do to make your trans live---If you decide NOT to rebuild the trans I would at the least get the trans re-tuned to eliminate the soft shifts---Also the stock tune locks the converter very slowly and at a low low 38 MPH----This makes your engine lug --hard on it as well as the trans---A retune will create firm crisp shifts as well as lock up the converter at a better 50-53 MPH and at a much firmer non slipping feel--
all of these things add life---
1/4 mile/AutoX
Joined: Jun 2014
Posts: 11,442
Likes: 2,187
From: Buffalo Texas
I do work myself (including trans overhaul),still I would have the trans done(have it done or get a replacement modified trans)with better than stock components and a really good converter !!!!
Melting Slicks
Joined: Nov 2009
Posts: 2,922
Likes: 219
From: West Branch, MI
If future mods are being thought of, I'd do the transmission while its out. Obviously, with a 3.42 and a stall going in, you're not a 'grandma' driver but a lot depends on what you're wanting out of it. I ended up where you're at when I did H/C/I and the trans started slipping. Even if you're a DIY'er, the hassle of doing something twice is still a PITA. Be honest with yourself, see where you're going with it and then plan accordingly.
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Pro
Joined: May 2014
Posts: 670
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From: Indiana
Also the stock tune locks the converter very slowly and at a low low 38 MPH----This makes your engine lug --hard on it as well as the trans---A retune will create firm crisp shifts as well as lock up the converter at a better 50-53 MPH and at a much firmer non slipping feel--
all of these things add life---
all of these things add life---
As far as rebuilding now, with what you have stated I would not rebuild the tranny now unless you've got money to spend now that you may not later. These same tranny's were put into 1/2 ton trucks weighing 75% more (unloaded) than the vettes. I got 200k miles out of the one in my 2003 Avalanche that was cammed and stalled.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
With a 3.42 rear end ---Locking the converter at 50 MPH happens at a minimum 2100 RPM's
With a stock rear gear of 2.73 it locks at 50 at a minimum 1600 RPM's
This is a fact--
Everyone may have different opinions on this--
My reasoning is that you want any shift or lockup to occur in the "sweet spot" of the RPM cruising range---This is between 2000 and 2500 RPM's----Not too high or not too low---Having it too low will cause the engine to lug--this is not only bad on the engine but the trans as well--The trans because the line pressure is too low--shifting or lockup with low line pressure is hard on the trans--period !----Line pressure is set by a TQ based table---The higher the TQ the more the line pressure---There is more TQ at 2100 than at 1600--so consequently more line pressure----
PS : I have set cammed and modded Silverado's that have an even higher 3.73 to lock up in 4th at 50 MPH----Customers sometimes will request a low 38 MPH lock up---but after driving it that way for awhile they always have me set it up to 50--as even with a 3.73 the engine lugs too much at 38 and the line pressure is too low causing sloppy shifts and even sometimes overheating
With a stock rear gear of 2.73 it locks at 50 at a minimum 1600 RPM's
This is a fact--
Everyone may have different opinions on this--
My reasoning is that you want any shift or lockup to occur in the "sweet spot" of the RPM cruising range---This is between 2000 and 2500 RPM's----Not too high or not too low---Having it too low will cause the engine to lug--this is not only bad on the engine but the trans as well--The trans because the line pressure is too low--shifting or lockup with low line pressure is hard on the trans--period !----Line pressure is set by a TQ based table---The higher the TQ the more the line pressure---There is more TQ at 2100 than at 1600--so consequently more line pressure----
PS : I have set cammed and modded Silverado's that have an even higher 3.73 to lock up in 4th at 50 MPH----Customers sometimes will request a low 38 MPH lock up---but after driving it that way for awhile they always have me set it up to 50--as even with a 3.73 the engine lugs too much at 38 and the line pressure is too low causing sloppy shifts and even sometimes overheating
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
With a 3.42 rear end ---Locking the converter at 50 MPH happens at a minimum 2100 RPM's
With a stock rear gear of 2.73 it locks at 50 at a minimum 1600 RPM's
This is a fact--
Everyone may have different opinions on this--
My reasoning is that you want any shift or lockup to occur in the "sweet spot" of the RPM cruising range---This is between 2000 and 2500 RPM's----Not too high or not too low---Having it too low will cause the engine to lug--this is not only bad on the engine but the trans as well--The trans because the line pressure is too low--shifting or lockup with low line pressure is hard on the trans--period !----Line pressure is set by a TQ based table---The higher the TQ the more the line pressure---There is more TQ at 2100 than at 1600--so consequently more line pressure----
PS : I have set cammed and modded Silverado's that have an even higher 3.73 to lock up in 4th at 50 MPH----Customers sometimes will request a low 38 MPH lock up---but after driving it that way for awhile they always have me set it up to 50--as even with a 3.73 the engine lugs too much at 38 and the line pressure is too low causing sloppy shifts and even sometimes overheating
With a stock rear gear of 2.73 it locks at 50 at a minimum 1600 RPM's
This is a fact--
Everyone may have different opinions on this--
My reasoning is that you want any shift or lockup to occur in the "sweet spot" of the RPM cruising range---This is between 2000 and 2500 RPM's----Not too high or not too low---Having it too low will cause the engine to lug--this is not only bad on the engine but the trans as well--The trans because the line pressure is too low--shifting or lockup with low line pressure is hard on the trans--period !----Line pressure is set by a TQ based table---The higher the TQ the more the line pressure---There is more TQ at 2100 than at 1600--so consequently more line pressure----
PS : I have set cammed and modded Silverado's that have an even higher 3.73 to lock up in 4th at 50 MPH----Customers sometimes will request a low 38 MPH lock up---but after driving it that way for awhile they always have me set it up to 50--as even with a 3.73 the engine lugs too much at 38 and the line pressure is too low causing sloppy shifts and even sometimes overheating
Last edited by enoniam; Jan 8, 2016 at 04:30 PM.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
It's not that simple----If you command the 3-4 shift point HIGHER than the TCC lockup speed in 4th gear---It doesn't matter where you set the TCC lockup even if 38 MPH It won't lock until after the 3-4 shift
If your 3-4 shift point say at 18% TPS is HIGHER than the 4th gear lock-up speed even if you set the lock up at 38---it won't lock up until the 3-4 shift happens--Sometimes they happen simostainiously or sometimes just after the 3-4 shift point---
Some people will tune the entire 4th gear lockup table to lock at 38 MPH ---But you have to realize that the 3-4 shift MUST happen 1st--for the TCC to lock--Without looking at your shift point table it is impossible to determine the MINIMUN RPM lock up in 4th
This is the most important part of tuning the lockup not to lock to early--The 3-4 shift point in stock trim happens at a much higher speed than the TCC lockup--so depending on how your shift table was altered or even more if just stock---It is rare that the TCC will ever lock up at such a low speed---If it does---It should be re-tuned to NOT allow such a low RPM lockup
This is quite confusing I know---The only way to be sure what's happening concerning lock up and shift points is to test drive the car----
If your 3-4 shift point say at 18% TPS is HIGHER than the 4th gear lock-up speed even if you set the lock up at 38---it won't lock up until the 3-4 shift happens--Sometimes they happen simostainiously or sometimes just after the 3-4 shift point---
Some people will tune the entire 4th gear lockup table to lock at 38 MPH ---But you have to realize that the 3-4 shift MUST happen 1st--for the TCC to lock--Without looking at your shift point table it is impossible to determine the MINIMUN RPM lock up in 4th
This is the most important part of tuning the lockup not to lock to early--The 3-4 shift point in stock trim happens at a much higher speed than the TCC lockup--so depending on how your shift table was altered or even more if just stock---It is rare that the TCC will ever lock up at such a low speed---If it does---It should be re-tuned to NOT allow such a low RPM lockup
This is quite confusing I know---The only way to be sure what's happening concerning lock up and shift points is to test drive the car----
Burning Brakes
Joined: Feb 2003
Posts: 1,144
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From: Panhandle FL
1/4 mile/AutoX
Joined: Jun 2014
Posts: 11,442
Likes: 2,187
From: Buffalo Texas
the overdrive is not meant to engage at low speeds and higher rpm's /// why do you think in trucks when hauling a trailer they don't want you to use overdrive ,if you have ever have torn one down you would see how there are less friction plates and small shafts in the the overdrive ???
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
It's not that simple----If you command the 3-4 shift point HIGHER than the TCC lockup speed in 4th gear---It doesn't matter where you set the TCC lockup even if 38 MPH It won't lock until after the 3-4 shift
If your 3-4 shift point say at 18% TPS is HIGHER than the 4th gear lock-up speed even if you set the lock up at 38---it won't lock up until the 3-4 shift happens--Sometimes they happen simostainiously or sometimes just after the 3-4 shift point---
Some people will tune the entire 4th gear lockup table to lock at 38 MPH ---But you have to realize that the 3-4 shift MUST happen 1st--for the TCC to lock--Without looking at your shift point table it is impossible to determine the MINIMUN RPM lock up in 4th
If your 3-4 shift point say at 18% TPS is HIGHER than the 4th gear lock-up speed even if you set the lock up at 38---it won't lock up until the 3-4 shift happens--Sometimes they happen simostainiously or sometimes just after the 3-4 shift point---
Some people will tune the entire 4th gear lockup table to lock at 38 MPH ---But you have to realize that the 3-4 shift MUST happen 1st--for the TCC to lock--Without looking at your shift point table it is impossible to determine the MINIMUN RPM lock up in 4th
This is the most important part of tuning the lockup not to lock to early--The 3-4 shift point in stock trim happens at a much higher speed than the TCC lockup--so depending on how your shift table was altered or even more if just stock---It is rare that the TCC will ever lock up at such a low speed---If it does---It should be re-tuned to NOT allow such a low RPM lockup
Pro
Joined: May 2014
Posts: 670
Likes: 46
From: Indiana
the overdrive is not meant to engage at low speeds and higher rpm's /// why do you think in trucks when hauling a trailer they don't want you to use overdrive ,if you have ever have torn one down you would see how there are less friction plates and small shafts in the the overdrive ???
Many trucks, especially gas versus diesel, often need the additional power when towing versus what they need when not, and get that from running a little higher rpms. Manufacturers have the trucks shifting into overdrive sooner rather than later in order to get their unloaded fuel mileage higher.
1/4 mile/AutoX
Joined: Jun 2014
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From: Buffalo Texas
10-29-2015, 03:38 PM #15
JordanVette97
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Originally Posted by norcalace View Post
With that logic just swap in 2.73s and you'll be hittin 200+ Are we to believe you have all that high performance work and parts and you can't tell when your A4 only shifted twice? Your tuner sounds like a genius. I'd follow his recommendations to the letter.
Shifts 3 times, no sense in being ignorant.. The car is 700rwhp and Chad himself has a 1600hp Z06.. Id like to see what you have.. He explained people do that because the 60e's are bad about tearing clutches in 4th
JordanVette97
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Originally Posted by norcalace View Post
With that logic just swap in 2.73s and you'll be hittin 200+ Are we to believe you have all that high performance work and parts and you can't tell when your A4 only shifted twice? Your tuner sounds like a genius. I'd follow his recommendations to the letter.
Shifts 3 times, no sense in being ignorant.. The car is 700rwhp and Chad himself has a 1600hp Z06.. Id like to see what you have.. He explained people do that because the 60e's are bad about tearing clutches in 4th
Pro
Joined: May 2014
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From: Indiana
10-29-2015, 03:38 PM #15
JordanVette97
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Quote:
Originally Posted by norcalace View Post
With that logic just swap in 2.73s and you'll be hittin 200+ Are we to believe you have all that high performance work and parts and you can't tell when your A4 only shifted twice? Your tuner sounds like a genius. I'd follow his recommendations to the letter.
Shifts 3 times, no sense in being ignorant.. The car is 700rwhp and Chad himself has a 1600hp Z06.. Id like to see what you have.. He explained people do that because the 60e's are bad about tearing clutches in 4th
JordanVette97
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Quote:
Originally Posted by norcalace View Post
With that logic just swap in 2.73s and you'll be hittin 200+ Are we to believe you have all that high performance work and parts and you can't tell when your A4 only shifted twice? Your tuner sounds like a genius. I'd follow his recommendations to the letter.
Shifts 3 times, no sense in being ignorant.. The car is 700rwhp and Chad himself has a 1600hp Z06.. Id like to see what you have.. He explained people do that because the 60e's are bad about tearing clutches in 4th
https://www.corvetteforum.com/forums...er-120mph.html
1/4 mile/AutoX
Joined: Jun 2014
Posts: 11,442
Likes: 2,187
From: Buffalo Texas
I looked up where you pulled that quote from. It is a gross understatement to say that there is a HUGE difference on the loads on the 3-4 clutches and the band between the 3-4 shift at WOT at 120 mph in a 700rwhp car as compared to nearly stock vettes and trucks at half or less of the rwhp, not to mention at the low rpms we are talking in this thread.
https://www.corvetteforum.com/forums...er-120mph.html
https://www.corvetteforum.com/forums...er-120mph.html
Pro
Joined: May 2014
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From: Indiana