What to do with a 1998 LS1?
M20 and M21 can handle 500 fwhp no problem and if your fortunate to have the M22 it can handle upwards of 700 fwhp. The only T56's that can handle those power numbers are built up T56's and the Mangnum versions are essentially TR6060's that can withstand 1000rwhp
I don't have a dog in this fight...but I'm gonna' have to throw the B.S. flag on this one.
They're pretty tough, but nowhere near up to the "true" 500-700 fwhp range.
(And I've got a pile of lunched old M20's and M21's under my bench to prove it...)
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Thread Starter
Teching In
Joined: Jan 2011
Posts: 16
Likes: 2
From: Louisiana
Cattle AC
Damn that’s not good news for me anyway. I’ll have to use the ones I have for now I guess. I guess it will be like the Russian dude in Rocky. “If he dies, he dies” ha.
I am going to keep putting cash aside. I have a set of marine diesels that I did not want to split up, but I am thinking of putting one up, so I can deal with the transmission dilemma later. The main issue it that an LS1 I had is not adequate for my power goals. Which is approx 500 hp.
I decided to cut the car with the 5.7 in it up and inventory what can be sold and sell it off. It has an automatic so it goes to.
I am going with a new iron LS platform 4.125 bore 9.240 deck and go for approximately 427 route. Shouldn’t be an issue acquiring my power goal.
At this point I only have the block and a set of bare heads being ordered. Once they arrive, they are going to the machine shop. Crank, rod and piston manufacturers have been chosen, but letting the machinist order them for me. After machining, crank balanced, heads assembled and cam made, it will come back to me for the rest. I hope this works out.
But after you assessment on my trannies I have, bummer. Guess better to know now. To bad a Jericho isn’t for regular driving.
Good To hear more opinions and advice.
Damn that’s not good news for me anyway. I’ll have to use the ones I have for now I guess. I guess it will be like the Russian dude in Rocky. “If he dies, he dies” ha.
I am going to keep putting cash aside. I have a set of marine diesels that I did not want to split up, but I am thinking of putting one up, so I can deal with the transmission dilemma later. The main issue it that an LS1 I had is not adequate for my power goals. Which is approx 500 hp.
I decided to cut the car with the 5.7 in it up and inventory what can be sold and sell it off. It has an automatic so it goes to.
I am going with a new iron LS platform 4.125 bore 9.240 deck and go for approximately 427 route. Shouldn’t be an issue acquiring my power goal.
At this point I only have the block and a set of bare heads being ordered. Once they arrive, they are going to the machine shop. Crank, rod and piston manufacturers have been chosen, but letting the machinist order them for me. After machining, crank balanced, heads assembled and cam made, it will come back to me for the rest. I hope this works out.
But after you assessment on my trannies I have, bummer. Guess better to know now. To bad a Jericho isn’t for regular driving.
Good To hear more opinions and advice.
Last edited by badazz; Jul 16, 2025 at 04:24 PM.
The M22 was rated at 400/400 in its heyday and was a bit more robust that the m20/m21. Seems low…and it is by today’s standards, but 400hp was an absolute crazy amount of power in the late 60’s-early 70’s when the M22 was new. I had an M22 in my 88’ truck I sold a few years ago. I replaced the factory 5 speed in that truck with the Muncie, and thought I was upgrading…
TECH Fanatic
Joined: May 2016
Posts: 1,292
Likes: 436
From: St. Louis
Is that 98' 4L60e still good and unopened? I'd take it for a spare if you don't need it for anything important 😜
Then again I'd field a powerglide if you have one of those sweet babies my favorite box slip and slide with power glide my first Chevy was a green 71 base model 4 door Chevelle 307" PG open 3.08:1 combo with no a/c and a factory white painted roof
Then again I'd field a powerglide if you have one of those sweet babies my favorite box slip and slide with power glide my first Chevy was a green 71 base model 4 door Chevelle 307" PG open 3.08:1 combo with no a/c and a factory white painted roof
Thread Starter
Teching In
Joined: Jan 2011
Posts: 16
Likes: 2
From: Louisiana
StockA4
The powertrain is in a ‘98 TransAm and was in perfect operating order. Never dogged. The set has been sitting for almost 3 years, that’s the only mistreatment to them. I just wanted a manual since it a truck. In a few cars I had we had power glides, 350’s, 400,s, C5’s and 6’s. I was the GM big block kid. My best friend was Fixed Or Repared Daily, lol. We were all automatics, except for some side trucks we had.
If they could be driven in the road, I’d just buy a Jericho. I am going to inquire about short limited standard driving with their’s, but I don’t think it’s recommended.
The budget for the truck body and chassis upgrades is set and will be in budget. Wheel package is a tad over, got paint locked in at 5k. The change to drop the 5.7 fucked the engine budget. Had 8k including motor, but looks like it could get to 14k possibly. So far just ordered block and set of bare heads. So it’s on now.
I looked into the T56 Magnum and has caught my serious interest. Looking at an easy 6k, that at this very moment is not doable.
This fall I am going to cut up the Firebird and see what I can salvage and what I can get for the parts. I’m sure I can get a little bit to help. The front clip is perfect and the rear liftgate, quarters and bumper are good. Who knows what the motor and trans would bring. I can document the low mileage, but prices are all over the place. Will help a little I suppose. I do still have months to try to get the transmission problem figured out. I have a few old 4-speeds laying around so worst comes to worst, I can still drive the thing.
I do have some marine power plants I could possibly put on the market, but I have not been able to let them go yet, ha!. I do have a job so I’ll figure it out.
The powertrain is in a ‘98 TransAm and was in perfect operating order. Never dogged. The set has been sitting for almost 3 years, that’s the only mistreatment to them. I just wanted a manual since it a truck. In a few cars I had we had power glides, 350’s, 400,s, C5’s and 6’s. I was the GM big block kid. My best friend was Fixed Or Repared Daily, lol. We were all automatics, except for some side trucks we had.
If they could be driven in the road, I’d just buy a Jericho. I am going to inquire about short limited standard driving with their’s, but I don’t think it’s recommended.
The budget for the truck body and chassis upgrades is set and will be in budget. Wheel package is a tad over, got paint locked in at 5k. The change to drop the 5.7 fucked the engine budget. Had 8k including motor, but looks like it could get to 14k possibly. So far just ordered block and set of bare heads. So it’s on now.
I looked into the T56 Magnum and has caught my serious interest. Looking at an easy 6k, that at this very moment is not doable.
This fall I am going to cut up the Firebird and see what I can salvage and what I can get for the parts. I’m sure I can get a little bit to help. The front clip is perfect and the rear liftgate, quarters and bumper are good. Who knows what the motor and trans would bring. I can document the low mileage, but prices are all over the place. Will help a little I suppose. I do still have months to try to get the transmission problem figured out. I have a few old 4-speeds laying around so worst comes to worst, I can still drive the thing.
I do have some marine power plants I could possibly put on the market, but I have not been able to let them go yet, ha!. I do have a job so I’ll figure it out.
I ran Jericho’s in my late models for years. They make a road race trans that I’m sure you could easily drive down the street. It would shift noisy…they all do…and the straight cut gears are whiney, but I’d bet it would work.
TECH Enthusiast
Joined: Nov 2017
Posts: 661
Likes: 91
From: S.F. East bay
so a m-22 can handle 700fhp out the gate or does it need to be worked…i have a ‘73 c10 swb fleet id like to do a muncie swap on….preferrabbly a m22 seeing how its already supercharged!!!
No. the M22 was rated at 400/400. I’ve seen more of them with broke ears or cases entirely, than actual working units. You want to go with the F-body magnum if you want a box rated for 700 torque. The standard magnum has too many shifter seal leak issues…the F-body magnum solves it and moves the shifter forward also.
TECH Enthusiast
Joined: Nov 2017
Posts: 661
Likes: 91
From: S.F. East bay
No. the M22 was rated at 400/400. I’ve seen more of them with broke ears or cases entirely, than actual working units. You want to go with the F-body magnum if you want a box rated for 700 torque. The standard magnum has too many shifter seal leak issues…the F-body magnum solves it and moves the shifter forward also.