There's plenty of GMT400 w/6.5's in wrecking yards to snatch a trans w/controller from too.
CK5
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What Better Gear Ratios For TH400 To Get To Just 70MPH In A 1983 C20 4 Door Dually 454 Carburated
- Thread starter blackandgold51
- Start date
There's plenty of GMT400 w/6.5's in wrecking yards to snatch a trans w/controller from too.
4L80E were also used behind 8.1L engines in various vehicles that couldn't package the Allison. Plus, unless you've snagged one from an H-1 Hummer, the newest TH-400 ("3L80") is from 1990. Most are much older, so the average 4L80 is a couple of decades younger.
The 454 will pull some high gearing ok at highway speeds..
Most vehicles they came in had 3:08's or 3:42's..
A 4L80E swap wont be cheap..
I'd try bigger tires first..245/75-16's aren't very tall,maybe 30"..
I notice a pretty good change in my trucks gearing when I put 265/75-16's on instead of the 245's...it felt almost too high geared with the bigger tires..(but if I had a 454 instead of a 6.2 I doubt it'd be as noticeable)..
The high stall converter is a bummer though,that may be half the problem..
I like the diesel converter with a low stall speed about 1600 rpms,it makes it feel more like a manual transmission,much less slippage on take offs and during shifts,less fuel waste too..unless the engine has a hot cam,you don't need a high stall speed converter ..
Most vehicles they came in had 3:08's or 3:42's..
A 4L80E swap wont be cheap..
I'd try bigger tires first..245/75-16's aren't very tall,maybe 30"..
I notice a pretty good change in my trucks gearing when I put 265/75-16's on instead of the 245's...it felt almost too high geared with the bigger tires..(but if I had a 454 instead of a 6.2 I doubt it'd be as noticeable)..
The high stall converter is a bummer though,that may be half the problem..
I like the diesel converter with a low stall speed about 1600 rpms,it makes it feel more like a manual transmission,much less slippage on take offs and during shifts,less fuel waste too..unless the engine has a hot cam,you don't need a high stall speed converter ..
You have not driven the 2 speed powerglide.
i use to have a 5.7L vortec crew cab 2wd long bed with 4.10 and 245/75/16 tires . if it was just the truck i did good in O/D . but if i hooked a trailer up i was better off in 3RD gear NON/OVERDRIVE .
i verified this from power / how far i had to push the gas pedal / and most efficient way was the vac gauge i had installed . the more vac you pull the more efficient you are .
and even the early days of the 700r4 they had a lot of problems . . . so dont think o.d. is the big ticket to better fuel mileage AND longevity of drive line parts .
i verified this from power / how far i had to push the gas pedal / and most efficient way was the vac gauge i had installed . the more vac you pull the more efficient you are .
and even the early days of the 700r4 they had a lot of problems . . . so dont think o.d. is the big ticket to better fuel mileage AND longevity of drive line parts .
Back in the 80's I had a 1977 C30 Dually with a 454/T400/Dana-70 (4.11 gears), and I built my own 1" body lift so I could install 33/12.50/16.5 tires on it. That thing could cruise 80-MPH down the Interstate for hours.
I agree 454 and 4.10 for 33" would be perfect if not for towing.
I think before you nail down a ratio and tire size you need to resolve the high stall converter.
If you get the taller gears you lower your rpms and slip the torque converter.
blackandgold51
1/2 ton status
No I haven't smh
The only time I have ever driven something with a 2-speed Power Glide was in something like this. It had a 3000 RPM stall speed, and a reverse lock out.
I had at least two old Chevy's with Powerglides--a '67 Impala with a tired 283,a '68 Caprice Estate Wagon with a 307,and my dad's '68 Chevelle wagon with a 307...pretty sure all 3 had 3:08 gears in the rear end too--"low" was good for a tad over 60 mph,"drive" was direct 1:1,so top end was only limited to the engines ability to push the car to its limit..
All of them topped out just over 90 mph..
Needless to say,acceleration was not blazing fast by any means--but the Powerglide was one of GM's most durable transmissions..supposedly they had a lower first gear ratio than any of the other automatics out at the time,but it sure didn't feel that way taking off on an uphill grade!..they also had a noticeable whine in neutral or park that no other transmission had too..the torque converter had a full time job making up for the lack of more gears..
All of them topped out just over 90 mph..
Needless to say,acceleration was not blazing fast by any means--but the Powerglide was one of GM's most durable transmissions..supposedly they had a lower first gear ratio than any of the other automatics out at the time,but it sure didn't feel that way taking off on an uphill grade!..they also had a noticeable whine in neutral or park that no other transmission had too..the torque converter had a full time job making up for the lack of more gears..
blackandgold51
1/2 ton status
The only time I have ever driven something with a 2-speed Power Glide was in something like this. It had a 3000 RPM stall speed, and a reverse lock out.
The only time I have ever driven something with a 2-speed Power Glide was in something like this. It had a 3000 RPM stall speed, and a reverse lock out.
Photo looks recent
That is not me. It is just a picture I got off the Internet. I do have some pictures of the altered dragster I owned, but it is just some old Polaroids from back in the days before Internet. I would have to have the pictures digitized, in order to post it on the Internet.
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The 2-speed Power Glide I had in my altered dragster was out of an old Chevy II that came original with a 4-barrel 327/2-speed Power Glide. A friend of mine had the Chevy II drive train sitting around in his garage, and he owed me some money for a 396 Big Block for his 1967 Stingray I sold him (which is still in the Stingray running to this day), so he just gave me the 327/Power Glide drive train. That 327 small block had a set of double hump heads on it that I had opened up to 1.80/2.02 valves, and bigger spring seats. Those heads are on a 1969 SS/RS Camaro also to this day.
My friend had a '62 Nova he bought to build up into a street/strip car,and it had an air cooled Poweglide in it!--no provisions for a cooler lines,it had fins on the torque converter...car had a 230 six originally..
He used a TH350 in it though.and I sold him a '69 350 out of a Suburban that was a 4 bolt main for it,after a 283 he tried rebuilding didn't pan out well..
He used a TH350 in it though.and I sold him a '69 350 out of a Suburban that was a 4 bolt main for it,after a 283 he tried rebuilding didn't pan out well..
Speed limits were 55 then, for fuel savings due to the oil embargo in the early 70's. Different times....
B
Bohemian
Guest
I don't believe you said what the stall rpm of your high stall torque converter was/is.
Assuming a stock grind cam, IMHO the high stall torque converter is the center of your problem, your 454 engine, tires you listed, 4:10 gears and th400 are not making your engine scream at 55-75 mph.
Get the right torque converter and you'll be happy with what you have.
Peace.
Assuming a stock grind cam, IMHO the high stall torque converter is the center of your problem, your 454 engine, tires you listed, 4:10 gears and th400 are not making your engine scream at 55-75 mph.
Get the right torque converter and you'll be happy with what you have.
Peace.
blackandgold51
1/2 ton status
Nope. It can't reach 75 mph at all. Only close to 65 past 60 and that's it
This explains about the stator in the torque converter,how it functions..
It can cause the vehicle to have many performance issues when it malfunctions..
Overrunning One Way Stator Clutch | Torque Converter
It can cause the vehicle to have many performance issues when it malfunctions..
Overrunning One Way Stator Clutch | Torque Converter
B
Bohemian
Guest
theres no reason why that truck with that engine, tranny and rear end ratio rolling stock with no mechanical issues can't peg that 85 mph speedometer all day long without the engine screaming...
Some Key things that can cause or contribute to the issue you describe is:
1. Torque Converter
2. Modulator is bad, out of adjustment or has a vacuum leak.
3. Valve body has issues.
You might want to consider taking the truck to a transmission shop for a transmission service, adjustment and diagnostic. Maybe its a simple as a bad modulator or getting the right torque converter for your combination.
Your transmission could also be so gummed up that the valve body is not functioning as it should.
peace.
