Re: [AMC-list] 151 4cyl trans to 258-6 interchange question

[Frank Swygert <farna@xxxxxxx>]

Both the 151 and the 258 used the SR4 transmission in 1980 according to the TSM. The gear ratios, however, are different. 

Gear  4cyl.  6cyl.
1st   4.07   3.50
2nd   2.57   2.21
3rd   1.66   1.43
4th   1.00   1.00
R     3.95   3.39

This shouldn't be a problem, but the torque rating of the transmission is usually dependent on the physical diameter of the gear, with a larger diameter gear (and higher ratio) capable of taking more torque. 

I would go ahead with it, but not "pound" on the car. When driven hard, the SR-4 is just adequate behind a six. I have a worn out one from a 79 Spirit that had 90K on it. 3-4 synchro is gone, had to hold it in 4th when driving, and most of the bearings were noisy also. I'm sure the thing was driven pretty hard by some kid just before I bought it for parts, but it WAS running and driving when I bought... just barely! If you're going to drive more normally you should be fine, but do a lot of burn-outs and other hard driving and it won't last long. 

A Mustang T-5 will bolt up to the SR-4 bell housing. You'll have to do a little research to find out which model (they have different input shaft lengths), but that's not hard. Got to www.theamcforum.com and search for "T-5 swap" and I think you'll find all the info you need. That would be the best bet, but can wait until the SR-4 gives problems. 

As far as I know the input shaft on the four and six cylinder AMC SR-4 are the same. You will want to get a six cylinder clutch -- it's stronger than the four cylinder version. The four cylinder uses a hydraulic clutch, the six the old style linkage in 1980. You can use the hydraulic setup on the six though. You might need to get a different slave cylinder or make a bracket for the existing one. The clutch arm will need to be changed too. 

I'm assuming you have a four cylinder car you're wanting to put the six in or have found a four cylinder four speed parts car. If the later, you need the clutch pedal as well as the master cylinder to use the hydraulic clutch, and I definitely recommend going that route over the mechanical linkage, but either will work fine. The four cylinder bell housing WILL NOT bolt to the six, you must have a six cylinder bell!

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Date: Wed, 24 Feb 2010 11:08:33 -0600
From: "Eddie Stakes" <eddiestakes@xxxxxxxxxxxxxxxxxxxx>

Claire below is wondering whether a 4sped trannie behind is 151 4cyl will stand up to a 258-6. I personally think it would those are indestructible little trannies, I believe a Chevy 350 will bolt up to it also. Regardless, if anyone here wishes to comment or advise, please feel free to and thanks in advance to all who might, be sure to copy your reply to Claire down below also who would appreciate it. 
Eddie Stakes
713.464.8825
eddiestakes@xxxxxxxxxxxxxxxxxxxx
www.planethoustonamx.com



From: Clair Maughan  heymaun@xxxxxxxxxxxxx   

     Hello,  Thanks for the visit about the 77 AMX Hornet drivers door and front fender.  Here's my e-mail address.  Could you also check on the 4 speed, if the AMX is heavier duty than the one behind the 4 cyl.  

--
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
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