8" vs. 9.5" Converter for TH400
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
8" vs. 9.5" Converter for TH400 Ok guys, I wanna see some debating on the pros and cons of an 8" converter vs. a 9.5" 
I need to decide soon what I want and its such a toss up for me right now.
I need to decide soon what I want and its such a toss up for me right now.
What sort of stall rpm are you looking at? I think that will drive your choice.
Not like you can get a 3500rpm 8" and once you get much over 4000rpm stall on a 9.5" you would be better served with an 8".
Not like you can get a 3500rpm 8" and once you get much over 4000rpm stall on a 9.5" you would be better served with an 8".
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
My builder said a 4500-4800 will work best for me. Not sure if i want to go that loose for street driving. I also dont want it to feel like I have one gear at part throttle because the looseness of the converter.
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
thanks for the responses.
I just talked to my builder and he thinks that a 9.5" may be best. He knows i want to hit it with a shot. He also said that he can stall a 9.5" at 4800 easily.
Just some background info on the guy doing my trans/converter: his name is Mike Ridings and he has built many motownmuscle members trans/converter combos. He is very well-known in Michigan. Most of his cars are grudge cars and some have been 7's or better.
We are going to discuss more about it tonight.
I just talked to my builder and he thinks that a 9.5" may be best. He knows i want to hit it with a shot. He also said that he can stall a 9.5" at 4800 easily.
Just some background info on the guy doing my trans/converter: his name is Mike Ridings and he has built many motownmuscle members trans/converter combos. He is very well-known in Michigan. Most of his cars are grudge cars and some have been 7's or better.
We are going to discuss more about it tonight.
Trending Topics
You can get an 8" to stall that low on nitrous as well, and not have to worry about the car sucking on motor with the bigger converter. I talked to coan, continental, edge, etc for my converter and every one of them said nothing other than an 8". So I have a great Protorque billet 9" core if you want it, since I have no use for it.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
No one has really stated why an 8" would be better. Is it more efficeint due to fin angle? etc. better on the street?
yes i know its lighter, but when it is already up and moving on the brake its really not a big deal over a few pounds.
I am open to anyone to give me their opinion, I just want a reason behind it and not just heresay on the internet (most of the people who posted in this thread actually do have experience with this swap/converter)
do you have an opinion on what to get or did you just come in here to ***** things up?
I would call around and get other opinions on what they recommend just to see. I had a 9.5" on my old (2002 combo) 355 nitrous combo that stalled to ~4500 NA and 5200 on the bottle but it was a dog in the 60 ft NA with the nitrous gearing. FWIW, I went with a 5700 8" from FTI on my solid roller 383 nitrous combo.
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
damn thats a huge converter!
I do like to drive the car on the street and it is not a track only car, I have this in the back of my mind as well
I have heard (no experience) that an 8'' can be brutal for the street and it feels like you are in neutral the whole time its that loose.
you could say efficiency is my main concern, what will be more efficient?
I do like to drive the car on the street and it is not a track only car, I have this in the back of my mind as well
I have heard (no experience) that an 8'' can be brutal for the street and it feels like you are in neutral the whole time its that loose.
you could say efficiency is my main concern, what will be more efficient?
My 9.5" 4500 stall was fine on the street. I would drive it anywhere. However, I did not like to drive it on the hwy(only went 60mph) as no overdrive sucks. The only thing that limits the streetability is heat generated by the higher converter but a good cooler will help. I will be running my 5700 on the street as I do not have a tow vehicle and will drive it to and from the track. The newer designs are not as bad as people think. It will be loose when you stab the throttle at low rpms but not bad. Talk to some converter builders and get their opinion. they are the experts and they will know what will work.
It will feel like your trans shifts very soft at part throttle cruising but that will save your u-joints
It will feel like your trans shifts very soft at part throttle cruising but that will save your u-joints
watch the video i have on youtube... "wicked94z teaser" it'll give you an idea of a spragless 5600 stall 8" on the street. A datalog from the track showed i 1-2 shifted at 6950 and it dropped to 6150.
No one has mentioned it yet, but why a 9.5" converter over a 9." The less mass on the crank the better, whether it be converter, trans fluid, etc. Yes the 8" converter will be more effecient than the 9.5" at your power level. You'd have to be making a lot of steam to get a 9" to go 4800 efficiently in a small block, and I don't think you'll be blowing through an 8" any less than 800 hp.
No one has mentioned it yet, but why a 9.5" converter over a 9." The less mass on the crank the better, whether it be converter, trans fluid, etc. Yes the 8" converter will be more effecient than the 9.5" at your power level. You'd have to be making a lot of steam to get a 9" to go 4800 efficiently in a small block, and I don't think you'll be blowing through an 8" any less than 800 hp.
What I was trying to say here is that different size converters are efficient at different rpm ranges and by the sounds of it you need a stall in the rpm range where an 8" is most efficient.
If you were doing an A4 and 9.5" would allow you to keep lockup then I would consider putting one to the stall you are talking about just for the lockup on the street.
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
watch the video i have on youtube... "wicked94z teaser" it'll give you an idea of a spragless 5600 stall 8" on the street. A datalog from the track showed i 1-2 shifted at 6950 and it dropped to 6150.
No one has mentioned it yet, but why a 9.5" converter over a 9." The less mass on the crank the better, whether it be converter, trans fluid, etc. Yes the 8" converter will be more effecient than the 9.5" at your power level. You'd have to be making a lot of steam to get a 9" to go 4800 efficiently in a small block, and I don't think you'll be blowing through an 8" any less than 800 hp.
No one has mentioned it yet, but why a 9.5" converter over a 9." The less mass on the crank the better, whether it be converter, trans fluid, etc. Yes the 8" converter will be more effecient than the 9.5" at your power level. You'd have to be making a lot of steam to get a 9" to go 4800 efficiently in a small block, and I don't think you'll be blowing through an 8" any less than 800 hp.
I am trying to understand why my builder is leaning towards a 9.5", like I said he is not just some random guy, he is fairly well-respected. I want to know his reasoning. I will keep all you guys updated on what is said when we talk about specs. I want to lean towards an 8", but the only thing holding me back is that it will be terrible to drive and that my th400 is going to feel like its in neutral the whole time its so loose.What I was trying to say here is that different size converters are efficient at different rpm ranges and by the sounds of it you need a stall in the rpm range where an 8" is most efficient.
If you were doing an A4 and 9.5" would allow you to keep lockup then I would consider putting one to the stall you are talking about just for the lockup on the street.
If you were doing an A4 and 9.5" would allow you to keep lockup then I would consider putting one to the stall you are talking about just for the lockup on the street.
That fear is unfounded. Listen to the more knowlegeable people on here. Once you're in the higher rpm stall ranges, the common impression that smaller feels looser is simply not true. I have a 4200 rpm 8" ATI in mine, and it is MUCH tighter feeling at part throttle than the 9.5" converter I tried in it that flashed to a similar rpm. Sort of the same results you see when comparing a 2800 stall 12" converter to a 2800 stall 9.5" converter ........the 9.5 feels much better.
Thread Starter
TECH Resident
iTrader: (10)
Joined: Oct 2008
Posts: 823
Likes: 0
From: DetroitRacing.com
That fear is unfounded. Listen to the more knowlegeable people on here. Once you're in the higher rpm stall ranges, the common impression that smaller feels looser is simply not true. I have a 4200 rpm 8" ATI in mine, and it is MUCH tighter feeling at part throttle than the 9.5" converter I tried in it that flashed to a similar rpm. Sort of the same results you see when comparing a 2800 stall 12" converter to a 2800 stall 9.5" converter ........the 9.5 feels much better.
Even tho it may sound like I an leaning towards 9.5", I am 100% unbiased. That is just what my builder tells me.
Pat, on the other end of it the first "high stall" I tried was a 2600 stall "level 10" 9.5" it ran hot and after I swapped it out for a 2800stall 9.5" Edge I realized the Level 10 drove like crap.
What the engine needs plays a part in how things drive too, you have something that is happy at the higher rpms and it will be fine. I would not want to try driving a stock motor with a 4000+stall though.
What the engine needs plays a part in how things drive too, you have something that is happy at the higher rpms and it will be fine. I would not want to try driving a stock motor with a 4000+stall though.