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  #1  
Old 04-15-2021, 12:16 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
258 Question

And yes, according to the VIN my jeep has the 258 instead of 232 as listed under my name.
Anyways, in our exploration of what we want to do, my dad and I have decided to keep the current engine until we get it to a point where we can drive it safely and comfortably, and after getting the body and frame are in a satisfactory condition we will do a powertrain swap.
But, seeing as it's mated to a three-speed, she has a real tough time getting over the fifty mark... so a new trans is in order... so anybody have recommendations for transmissions that are fairly inexpensive for the 258? Were thinking something like a 5 speed manual.
And since we have no idea what this engine has gone through or how many miles it has, we want to rebuild it... are there any rebuild kits out there, or is it better to get a new one?
Any suggestions or ideas would be greatly appreciated.
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  #2  
Old 04-15-2021, 01:57 PM
Heep-J4000's Avatar
Heep-J4000 Heep-J4000 is offline
258 I6
 
Join Date: Feb 09, 2014
Location: Schoorl ,the Nederlands
Posts: 316
The 258 isn't a bad engine for what I know ,lot of CJ owners did swap them for the 3.8 they had.

Don't know if you have a manual three speed or automatic transmission!?

My j-4000 had a T15 three speed behind a 360 and was fast and good enough to drive it anywhere every day!
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http://www.ifsja.org/forums/vb/showthread.php?t=180974

99' Dodge ram 2500 4x4 crew cab 5.9 Cummins ,backup work truck for now
73' Jeep J4000 (named Heep or Desert Dragon) amc 360 V8 converted to LPG with T15/D20 (was my daily work truck for thirteen years and is going to have major overhaul
80' Jeep cj5 350 V8 Chevy/ms420/D300 (a slow ongoing never finished project)

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  #3  
Old 04-15-2021, 03:40 PM
bufurd's Avatar
bufurd bufurd is offline
327 Rambler
 
Join Date: Apr 13, 2008
Location: ashland wi.
Posts: 581
The 258 is a great engine, the 3 speed is a fine transmission, what keeps you from getting it much over 50? Power or ya think it’s over reving?

I’m curious about your handle,, Junkers456. Is it pronounced Yunker?
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  #4  
Old 04-15-2021, 09:11 PM
backroadin''s Avatar
backroadin' backroadin' is offline
350 Buick
 
Join Date: Aug 11, 2004
Location: Vermont
Posts: 948
If the rpm's aren't topped out at 50, then more gears won't help the speed. Top gear on a 3 or 4 spd is 1:1 ratio, and a 5spd would be even higher with the overdrive. (4th is usually 1:1 on a 5spd.) A lot of 4cyl. baby jeeps with 5speeds are pretty doggy in 5th because of the lack of power.

As to tranny options, a t-177 (j-truck) or t-176 (CJ) would be a good 4spd option. they are close ratio (no granny gear). For 5spds, the wrangler ax-15 is a good option although getting expensive to find I think. The earlier wrangler 5spd was the ax-5 I believe, and would be OK if you weren't hoggin' it. Any Jeep tranny will bolt up to your 258 if it was behind a jeep engine. However, depending on which side your front diff is on, you'll have to make sure the t-case drop is on the same side if you're getting a tranny/tcase combo. Otherwise, an adapter plate should mate any tranny to your existing t-case. Any non-AMC tranny will need an adapter plate to bolt to the engine, but if you find one you like with a t-case with the proper side drop, you could go that route too. Staying Jeep/AMC will usually save you cash since adapter plates can be expensive. There is lots of info on tranny swaps here, too.
Then there's the small stuff like matching the pilot bushing to the input shaft, fabbing clutch linkages or swapping to a hyd. clutch setup if you go with a tranny that comes with one. You'll probably need to move the crossmember, too. And then you'll need to shorten the rear driveshaft and lengthen the front depending on the overall length of the setup.... a 5spd will definitely be longer than your 3spd. Lots to consider, but it's all plenty doable. Finding a tranny that can bolt to your tcase or has a tcase with the same side drop will save you some cash. Adapter plates can be expensive. Plan on doing the driveshafts regardless - pretty much any tranny will be longer than a 3spd. If you can find a donor rig with a tranny /tcase you want and can get the front driveshaft too, that'd be even better. If it's the same kind of rig as yours, swipe both driveshafts.

Engine rebuild kits: pretty much any name brand kit will do fine, and there are lots of options for the 258. You can do a 4.0 head swap if you really want more oomph. There is lots of info on hopping up or freshening up the 258 here and elsewhere on the net. Best of luck.
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  #5  
Old 04-16-2021, 10:34 AM
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tgreese tgreese is offline
 
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,425
Yes, top speed is limited by power, not gearing. Year, model, equipment would help.

Any Jeep built with the 258 (earliest 1971) is capable of speeds well over the legal speed limit. Something else is wrong. A different transmission won't help.
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Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
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Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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  #6  
Old 04-16-2021, 11:44 AM
Miner_Jeepy's Avatar
Miner_Jeepy Miner_Jeepy is offline
230 Tornado
 
Join Date: Mar 17, 2019
Location: OH
Posts: 19
To parrot what others have said your concerns are power and gearing. Power gets you to speed and gearing determines how fast you can go. It will sound dumb but you may want to confirm that all your gearing is stock. While it's unlikely it's possible that the previous owner regeared the thing with deeper axle gears limiting your top speed.

From there it's a power thing. Not going 50 is bold. Are you sure you're reaching wide open throttle? Not sure if you've done basic maintenance stuff like wires and a carb clean. You will probably have to nickel and dime your way to what you want. Unless you have like zero compression in which case you're in for a time.
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  #7  
Old 04-16-2021, 12:07 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
Quote:
Originally Posted by Heep-J4000
The 258 isn't a bad engine for what I know ,lot of CJ owners did swap them for the 3.8 they had.

Don't know if you have a manual three speed or automatic transmission!?

My j-4000 had a T15 three speed behind a 360 and was fast and good enough to drive it anywhere every day!
Its the manual... and I'm guessing that even though the odometer says ~60,000, it really has upwards of 200k, if not more.
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  #8  
Old 04-16-2021, 12:10 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
Quote:
Originally Posted by backroadin'
If the rpm's aren't topped out at 50, then more gears won't help the speed. Top gear on a 3 or 4 spd is 1:1 ratio, and a 5spd would be even higher with the overdrive. (4th is usually 1:1 on a 5spd.) A lot of 4cyl. baby jeeps with 5speeds are pretty doggy in 5th because of the lack of power.

As to tranny options, a t-177 (j-truck) or t-176 (CJ) would be a good 4spd option. they are close ratio (no granny gear). For 5spds, the wrangler ax-15 is a good option although getting expensive to find I think. The earlier wrangler 5spd was the ax-5 I believe, and would be OK if you weren't hoggin' it. Any Jeep tranny will bolt up to your 258 if it was behind a jeep engine. However, depending on which side your front diff is on, you'll have to make sure the t-case drop is on the same side if you're getting a tranny/tcase combo. Otherwise, an adapter plate should mate any tranny to your existing t-case. Any non-AMC tranny will need an adapter plate to bolt to the engine, but if you find one you like with a t-case with the proper side drop, you could go that route too. Staying Jeep/AMC will usually save you cash since adapter plates can be expensive. There is lots of info on tranny swaps here, too.
Then there's the small stuff like matching the pilot bushing to the input shaft, fabbing clutch linkages or swapping to a hyd. clutch setup if you go with a tranny that comes with one. You'll probably need to move the crossmember, too. And then you'll need to shorten the rear driveshaft and lengthen the front depending on the overall length of the setup.... a 5spd will definitely be longer than your 3spd. Lots to consider, but it's all plenty doable. Finding a tranny that can bolt to your tcase or has a tcase with the same side drop will save you some cash. Adapter plates can be expensive. Plan on doing the driveshafts regardless - pretty much any tranny will be longer than a 3spd. If you can find a donor rig with a tranny /tcase you want and can get the front driveshaft too, that'd be even better. If it's the same kind of rig as yours, swipe both driveshafts.

Engine rebuild kits: pretty much any name brand kit will do fine, and there are lots of options for the 258. You can do a 4.0 head swap if you really want more oomph. There is lots of info on hopping up or freshening up the 258 here and elsewhere on the net. Best of luck.
Good stuff! Many thanks.
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  #9  
Old 04-16-2021, 12:16 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
The engine is probably just real tired. I think it has over 200k on the engine, even though it says it has under 60k... as to the name, I say it Junkers (derived from the german manufacturing company), but only because people can't wrap their head around a "J" being pronounced as a "Y" lol
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  #10  
Old 04-16-2021, 12:18 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
Quote:
Originally Posted by Miner_Jeepy
To parrot what others have said your concerns are power and gearing. Power gets you to speed and gearing determines how fast you can go. It will sound dumb but you may want to confirm that all your gearing is stock. While it's unlikely it's possible that the previous owner regeared the thing with deeper axle gears limiting your top speed.

From there it's a power thing. Not going 50 is bold. Are you sure you're reaching wide open throttle? Not sure if you've done basic maintenance stuff like wires and a carb clean. You will probably have to nickel and dime your way to what you want. Unless you have like zero compression in which case you're in for a time.
I doubt its getting enough fuel, carb prolly needs to be gone through, so on and so forth. Fuel lines and pump, and probably the tank, all need to be replaced. We have to give 'er the ol' Italian treatment (carb/choke cleaner down the carb) along with a couple ounces of fuel right down the chute just to get her started.
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  #11  
Old 04-16-2021, 05:55 PM
backroadin''s Avatar
backroadin' backroadin' is offline
350 Buick
 
Join Date: Aug 11, 2004
Location: Vermont
Posts: 948
Quote:
Originally Posted by Junkers456
but only because people can't wrap their head around a "J" being pronounced as a "Y" lol
Jagermeister FTW!!!!

Lol! I've heard a rumor that Mic Jagger's last name was really Jager, (Yeager) but he went with the "J" sound and Jagger is a much better rockstar name.

One more German factoid before we get back on topic: the deer on the jagermeister logo is because jager is german for hunter, and of course meister being master - ergo jagermeister means "master hunter".

What year and model is your rig?
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"Roads? Where we're going we don't need roads." -- Dr Emmett Brown

"When this baby reaches 88 miles per hour, you're gonna to see some serious sht!"

73 Wagoneer - 4.6L Stroker (yeah baby!!) t176/d300, 3.73's, 33" muds, 4"spring lift, 2" body. Offy dualport w/ Quadrajet, pertronix, flowmaster.
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  #12  
Old 04-19-2021, 12:28 PM
Junkers456 Junkers456 is offline
232 I6
 
Join Date: Nov 30, 2020
Location: Dickinson, North Dakota
Posts: 40
Quote:
Originally Posted by backroadin'
Jagermeister FTW!!!!

Lol! I've heard a rumor that Mic Jagger's last name was really Jager, (Yeager) but he went with the "J" sound and Jagger is a much better rockstar name.

One more German factoid before we get back on topic: the deer on the jagermeister logo is because jager is german for hunter, and of course meister being master - ergo jagermeister means "master hunter".

What year and model is your rig?
1979 Jeep Cherokee (according to the badging). There's a picture post I did awhile back if you wanna see her... shes in rough shape.
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  #13  
Old 04-21-2021, 06:20 PM
jpcoutts's Avatar
jpcoutts jpcoutts is offline
304 AMC
 
Join Date: Jun 28, 2002
Location: Hot Springs, Arkansas
Posts: 2,040
A J10 I had 30 years ago that had a 258 and wouldn't get up to 60 on the interstate and slowed down considerably on hills, it was worn out and nothing made it any better until I replaced it. You might do a compression check or check the valves but with that many unknown miles it's likely doing all it can. Do you have a compression tester, if not AZ or one of the other places will lend you one. You might even try putting a wrench on the crank (after removing the coil Wire!) and see what happens when you turn the engine over by hand. If it turns easily or you hear the cylinders leaking down it's just a tired engine. Good luck!
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