455 on TH350 or 400
#3
You can build a 350 to live behind a 455 and it is a lighter transmission so you will save weight but it does cost a lot. A stock 400 will hold up to a 455 with no modifications depending on how much hp and torque you build into the 455. If is stock or medium build no problem.
Other tranny experts will chime in with other opnions
Other tranny experts will chime in with other opnions
#4
Buddy of mine must have gone through 3+ TH350 behind his 455. I have to admit he's a bit hard on them but regardless I'd go with the TH400. I've beaten the snot out of mine behind a 455 and now it's behind a 330 and still going strong.
#6
X2 on the 400. I went through at least 3 in my Chevelle when I was a kid. Very hard on them. I switched to a 400 and NEVER had a problem. That thing was just STRONG! You can really feel the fullness of the shifts. I know that sounds corny but its true.
#8
A properly built TH350 will live behind a stout 455 no problem. Machine the direct drum piston so you can install 5 clutches, dual feed the direct drum (either with a shift kit or removing the center seal), install a hardened intermediate sprag race, and pay attention to the clearances and you will be fine. I have built several TH350 that run in the high 10 with the above modifications. A TH400 is obviously a stronger unit, its also much heavier.
#9
How much heavier? I found this on a Chevy site.
I measured a TH350, TH400, and 4L80E all on the same scale on the same day.
Weights were
TH350 short tail- 125 lbs.
TH400- 134 lbs.
4L80E- 178 lbs.
My opinion is that going with a turbo 350 is like trying to drive a golf ball with a 3 iron. Yeah, you can do it, but you have to hit the snot out of it and it won't go quite as far. A turbo 400 from a junk yard would probably live in front of most motors.
I measured a TH350, TH400, and 4L80E all on the same scale on the same day.
Weights were
TH350 short tail- 125 lbs.
TH400- 134 lbs.
4L80E- 178 lbs.
My opinion is that going with a turbo 350 is like trying to drive a golf ball with a 3 iron. Yeah, you can do it, but you have to hit the snot out of it and it won't go quite as far. A turbo 400 from a junk yard would probably live in front of most motors.
#13
I had a hard time finding factory parts at salvage yards for my kickdown switch so I just made my own bracket on the pedal, bought the factory switch and wired it myself. Works great.
I killed a well built TH400 behind a fairly stock 455.
A TH350 would be best for weight/power but I would not expect it to last.
I killed a well built TH400 behind a fairly stock 455.
A TH350 would be best for weight/power but I would not expect it to last.
#14
FYI, look at the accelerator pedal on early 80s G-body cars. Many of these used a very similar switch to disable the A/C compressor at W.O.T. These should be more readily available at wrecking yards.
#16
I use a th350 in my car. I obviously abuse it. Installed it to reduce weight and increase HP over the 400s I had been using. It wasn't cheap but it has done very well. Here is a tech article for ya:
http://www.dragracingonline.com/tech..._7-olds-1.html
http://www.dragracingonline.com/tech..._7-olds-1.html
#17
If its a stock motor and is to be street driven only, and you are going to purchase a trans, then you should seriously consider going with an automatic overdrive unit. The 200 - 4R is great for fuel economy on the road!! It is still even OK on a mild Street/Strip application!
#18
TH400 Long Shaft ??
Hi Guys,
MY TH400 is out of a 68 delta 88...it looks like it is a long shaft. Any issues using this on my supreme. I have it in now and had to drill a couple of holes for the cross member. I am just a little concerned when i lay the body back on.
I know I have to shorthen the driveshaft
MY TH400 is out of a 68 delta 88...it looks like it is a long shaft. Any issues using this on my supreme. I have it in now and had to drill a couple of holes for the cross member. I am just a little concerned when i lay the body back on.
I know I have to shorthen the driveshaft
#22
I have a stock rebuild 400 that I beat the snot out of behind a 13.001 second street tire car in high school. After sitting in the garage floor for 14 years it is now behind my 500 HP / 550 TQ engine and it is still going strong. I'll trade the power loss for the ruggedness all day long.
I'd say a $350 rebuild on a stock TH400 that last 20 years behind most anything is well worth it
I'd say a $350 rebuild on a stock TH400 that last 20 years behind most anything is well worth it
#23
Hi Guys,
MY TH400 is out of a 68 delta 88...it looks like it is a long shaft. Any issues using this on my supreme. I have it in now and had to drill a couple of holes for the cross member. I am just a little concerned when i lay the body back on.
I know I have to shorthen the driveshaft
MY TH400 is out of a 68 delta 88...it looks like it is a long shaft. Any issues using this on my supreme. I have it in now and had to drill a couple of holes for the cross member. I am just a little concerned when i lay the body back on.
I know I have to shorthen the driveshaft
#25
If you have a block off plate blocking the hole that the speedometer gear housing would go into then you'll be able to find all the parts you need here:
http://www.transmissioncenter.net/sp...____va.htm#400
http://www.transmissioncenter.net/sp...____va.htm#400
#26
If you have a block off plate blocking the hole that the speedometer gear housing would go into then you'll be able to find all the parts you need here:
http://www.transmissioncenter.net/sp...____va.htm#400
http://www.transmissioncenter.net/sp...____va.htm#400
I should get a pic but I see a plate but it is not in the very tail piece...it is right before the tail piece. Should there be a block off plate ?
#28
#29
That's the right spot, does it have a freeze plug in it because it doesn't look like a bolt on cover.
If you look at my build page (see link in above signature) you'll see where I changed mine out. Its on page 4 I believe.
If you look at my build page (see link in above signature) you'll see where I changed mine out. Its on page 4 I believe.
#30
its not a bolt on so I guess its a freeze plug...
I am not sure what i need to order...my TH350 had the orange gear with a 2.56 rear end. How do I know what to order for the Th400.
I am starting to think I should clean up my TH350 and put in back in.
#32
Thanks...that could be the case here. It did not look like a plug to me but I do have it painted. If it is not the 350 is going back in.
#33
After a closer look today...it looks like an untouched casting so it is not a plug. Thanks for the heads up...not sure if I can get rid of this thing.
#36
They are similar Th350: 1st - 2.52, 2nd - 1.52
TH400 1st - 2.48, 2nd - 1.48
I actually have a low gear set in my TH400 which I believe uses the TH350 ratios. It's noticeable but I wouldn't call it Earth shattering. I will say that 1st gear seems to fly by but that could be a function of the Switch Pitch also, dunno. Oh yeah, my 4.10s don't help the equation, lol
TH400 1st - 2.48, 2nd - 1.48
I actually have a low gear set in my TH400 which I believe uses the TH350 ratios. It's noticeable but I wouldn't call it Earth shattering. I will say that 1st gear seems to fly by but that could be a function of the Switch Pitch also, dunno. Oh yeah, my 4.10s don't help the equation, lol
#40
Did you get this problem solved CL? You can use the Th400 Converter off of the 455 on your Th350 SO LONG AS, it wasn't a variable pitch Th400 unit. That Speedo isn't machined out because that trans was from one of the older boat cars that ran the speedo off the front, I believe, left wheel. Can you get rid of that Th400? Sure can. If you were close to me, I'd be asking what you wanted for it just for the hard parts in it, and even moreso if it were VP. So you didn't just toss it away or scrap it I hope. And its still a good case if you found someone running a Chevy or GMC 4x4 truck with BPO motor like I am inclined to do. All I'd have to do is use a Chevy output shaft to mate that trans to my Transfer case, and the speedo drive gear goes into the Transfer case on a a 4x4, not the transmission. So yes, even the case, it's useable to someone.
Last edited by hotrodpc; June 24th, 2012 at 10:57 PM.