[Johnny406]

I recently picked up a manual VB race prepped 1.76 PG for my car. Long story short, I broke my TH400 for the 3rd time and decided to try something different. At about 3240 race weight, I know my car is still a little heavy for a PG but I am planning on going to a full fiberglass front this offseason and will find more weight to gut. That and my next motor, a forged crank 4 bolt 428 will be much more RPM friendly for the glide.


Anyways, this past weekend was our final race of the year and I pushed hard to get the new tranny & converter in (Preacher Tom's old 3800 Coan converter) and a new driveshaft made as well as a gear swap from 3.31's to 3.73's that I had. I was able to make it to the track and we had a 4+ hour delay due to electrical problems. So on my first and only qualifying pass I did a light burnout and more of a shakedown run. The car certainly didn't launch hard, the 3.73 x 1.76 combo had nothing on the 3.31 x 2.75 first gear ratio of the TH400. For my next blunder I shifter way too soon so it took awhile to get the car back in the powerband and I passed my opponent at the line and still ran a 13.82 ( thought it would be slower). Sadly that was the only run as there was another long delay on a oil down and then my makeshift tranny cooler line failed and made a heck of a mess in the staging area


Now for comparison, the last run I did before breaking the tranny, I ran a new personal best on motor, a 12.067 @ 112.90 on a double breakout loss (oops) to the eventual race winner. Though a 1.753 second drop in performance is excessive, it would've been far less if I hadn't shifted around the 200ft mark and if I had a better starting line ratio.


Am I asking too much out of my 455 at this weight to really consider trying a glide? The TH400 is at the trans shop now, I'm trading in the lower 2.75 gearset for a stock 2.52 which should work better for hard tire racing 1/8th mile if I go back to it.

[Johnny406]

I failed to mention that Pueblo Motorsports Part is at 4900 ft elevation.

[grandville455]

Needs a 1.80 first gear, my buddy runs one in his 3700 lb chevelle, runs mid 9's, also most people don't use enough stall when going to a glide

[cgeise]

same as above 1.80 gear set and a loose convertor maybe in the 5k or more range

[Johnny406]

Originally Posted by cgeise

same as above 1.80 gear set and a loose convertor maybe in the 5k or more range

Wow, that much. I went to the 3800 which is by far the loosest converter I ever used.

[dragracerx2813]

A 1.80 gear will help . But you definitely need more converter .

[ejw]

I would add a little more gear also maybe 4.10, especially w heavy car. Though not sure how talll your tires are. I have 30” tall tire w 4.56 gear, 4900 stall, 1.80 pg, 4200lb car 1/8mile.

[jimmy daniel]

More converter. In my 1.80 glide 4.56 rear Tempest, I ran a 6000 stall converter before I hurt the motor. The 535 I’m having built I am going to try around 62-6300 Hughes converter. That glide just wants to be looser.

[Probird]

What size tire are you running? When I switched to a glide I only lost .02 in 60' and picked up 2 tenths overall in the 1/8th and I was at 3340 lbs. I was at 7.20's in the 1/8th before and 7.0's after the switch. Something is way off. That converter isn't doing you any favors. I'd say minimum of 4800 stall. Most likely need more gear too. I had a 31-13 slick and had 4.88 gears. That was a long time ago. You won't notice any difference going to a 1.80 first gear. I switched and gained nothing but peace of mind that it wasn't going to break the planetaries. That 1.76 will hold up a long time at your power level. Now I'm at 3275 race weight with a 4.11 gear and the converter stalls at 6300 going low 9's.

[S/st 54]

Originally Posted by Johnny406

Wow, that much. I went to the 3800 which is by far the loosest converter I ever used.

I'm a fan of the Glide! It opens your tuning window using nitrous also.
As mentioned above the 1.80 first gear would help you.
The looser converter will help get your motor up in it's power range up stairs quicker and keep it there longer,regardless if your using the juice or not,And at that altitude ,as you know, the motor takes a bit to get upstairs. Like the others have said a steeper rear gear would help also.

[ponyakr]

"...I broke my TH400 for the 3rd time..."


Just curious as to what you broke. The reason I ask is because my first 455 broke the stock 16 element intermediate sprag, in 2 TH400's. After a local trans guy told me I needed a 34 element sprag, I've always run one & never broke another.

https://www.ebay.com/itm/4L80E-TH400...EZQb:rk:3:pf:0

But, if you've broken three 34 element sprags, then there is a stronger 36 element sprag set-up. TH400's have been used in some very high power cars. So, yours can probably be built to live behind your engine.

http://www.jakesperformance.com/th400/

But, if you're bracket racing, the Glide should make it a little easier to hook & run more consistent ET's. The Glide can be built to withstand big power. But, at anything close to stock, a decent 455 will break it. A local trans guy, who built lots of Glides for 10 & 11 sec sbc cars, built one for me. My 455 broke it in the time trials. Never got to race it, & never tried another.

[Johnny406]

Gentlemen,

Thank you all for your input. This PG is a totally new and different mentality for me. No doubt you gentlemen have a much better grasp on this than I do. I thought with our RPM limited Pontiacs, we would blow through the converter if it was too loose. Since I was running a 3200 converter I thought a 3800 would be a good start as I read that in a PG handbook. I really didn't think the 3.73's would be the long term answer but I knew if I kept the 3.31's in it, the car would've been a total pig off the line (not that it was great by any means). before, the car had a good 2nd half of a quarter mile race BUT I do a lot of 1/8th mile heads up as well. The 2.75 1st gear of my TH400 made it hard to launch on hard tires, even with tire prep but now I suspect lot of that problem was using a too tight of a converter. The TH400 is in the shop now, I should find out what I broke this time on Friday. He suspected I melted the clutches together since it is stuck in a forward gear but the fluid looked and smelled clean when I drained it.


When bracket racing I use Hoosier QTP 27x10x15's, when hard tire racing I use Pep Boys Futura 295-50-15's

[ponyakr]

"...The 2.75 1st gear of my TH400 made it hard to launch on hard tires, even with tire prep but now I suspect lot of that problem was using a too tight of a converter..."

Don't guess I understand the logic of that statement. A tighter converter should be easier on hard tires, not harder.

I used a stock 13" converter in all our 455 bracket cars, in order to get max traction, even on bad tracks with no prep. A looser converter would have run quicker, on good tracks with max traction, but, would have produced lots of wheel spin on bad tracks.

If you wanna get really serious about hard tire racing, you need to find out what the guys in the F.A.S.T racing series are doing. Some of those guys are running unbelievable times, on hard, NARROW tires. But, they know all the suspension & traction tricks.

I assume there are guys here who know something about that deal. I know Cliff has said he's had Q-jets running in that series. Don't know how many of their hard tire traction tricks he's picked up. And, I don't know how many guys from that series will give any of their traction tricks to others.

https://www.fastdrags.com/

https://www.hemmings.com/magazine/mu...b/1860445.html

https://www.hotrod.com/articles/dave...h-road-runner/

http://classracer.com/magazine/?p=5493

https://www.hotrod.com/articles/trac...p-suspensions/

[Big Mike]

I'd like to know what you keep breaking. Not to b e a smart ass, but a 12 second car shouldn't be breaking a turbo 400. Mine runs mid tens at about the same weight and during inspections I find no wear on anything even after a couple of hundred passes. Somethings not right in that 400.

[Johnny406]

Originally Posted by Big Mike

I'd like to know what you keep breaking. Not to b e a smart ass, but a 12 second car shouldn't be breaking a turbo 400. Mine runs mid tens at about the same weight and during inspections I find no wear on anything even after a couple of hundred passes. Somethings not right in that 400.

Fair question and I kinda wondered the same thing myself. I asked the tranny shop to go through that case very hard to see if there is some sort of breakage or distortion or something.

[ponyakr]

"...Not to b e a smart ass, but a 12 second car shouldn't be breaking a turbo 400..."


My 12 sec 455 broke the 16 element int sprag in two TH400's. The 2nd one was in a supposedly "full competition" reverse valve body TCI TH400. BUT, for some reason, TCI left the stock 16 element sprag in the trans. Maybe they thought my old Pontiac engine didn't have enuff power to break it & they'd make a few extra dollars profit.

A similar 455 broke the sprag outer race in a TH350 I bought, which came out of an 11 sec Nova. Bought a TCI hardened outer race. Broke that race into several pieces, I assume because it was more brittle than the stock race. The sprag is the weak link in a TH400. In a TH350, it's the sprag outer race. We broke all those parts on the 1-2 shift, at 5000rpm. There are 34 & 36 element sprag upgrades for the TH400 & 36 element sprag/drum/race upgrades for the TH350.

It's not the hp that kills 'em, it's the big torque of the long stroke Pontiac that breaks the trans.

[Jack Ferris]

I have at least 1500 9 and 10 second passes (4500 ft track) on my T400 that still retains ALL of the original hard parts. Been in service for 27 years. I have replaced one case due to a driveshaft failure and I replace individual clutches/steels as needed. Still retains some of the originals. Same 34 element sprag that I put in it in 1991. I did upgrade the the rear selective bushing to a torrington. Nothing special but decent clutches, a TCI brake and the 34 sprag. It's been behind 2 different motors starting at 600 and ending at 740. My bowtie friends are always asking why I haven't moved to a glide. For me, I see no point. I'm a bracket racer so set on kill ET/MPH matters not. I have been told they are more consistent but have yet to see it in their 3000-3400 pound cars.

As far as your car John, and this is personal opinion, it's a little too heavy and it needs more gear, converter and HP to make the glide work better than a 400.

[Johnny406]

Do you guys think I will run out of gear for 1/4 mile bracket racing (no nitrous) if I went to a 4800 converter on a 4.10 gear with the powerglide? Though bottom filled, my motor is a stock crank 2 bolt 455.

[Jack Ferris]

What is your trap MPH now?

[ponyakr]

If you have H-beam rods, it should be safe to 6000 rpm. But, how high will your cam make power ?

I don't recall seeing what cam you're running.

If your cam quits pulling at just over 5000, then you probably don't wanna gear for crossing at 6000.

There are online rpm calculators. You can input various gear ratios, tire sizes, & mph.

https://www.google.com/search?q=rpm+...hrome&ie=UTF-8