DRUMMER35501 Posted February 2, 2007 Share Posted February 2, 2007 Hey guys, I really need some assistance here. I have recently purchased a B61T and it has the end673 with a trd67 tranny and 4.25 ratio on rear end according to build sheets and I am thinking about changing the engine and swapping the tranny to an Eaton Fuller. What engine and tranny would fit or would I be better of to rebuild the old engine. I plan on hauling my antique tractors to shows and parades with this old truck. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/2097-end-673-with-a-trd67-tranny/ Share on other sites More sharing options...
Freightrain Posted February 2, 2007 Share Posted February 2, 2007 Beside a 237/250/285 motor, nothing else will really fit in the engine bay.How heavy are going to be? I pull 14K trailer around with my ol 673 without much trouble. Coming up on 50 yrs old and still purr'n without using much than a qt of oil all summer(maybe 5K miles/yr). Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/2097-end-673-with-a-trd67-tranny/#findComment-10220 Share on other sites More sharing options...
Brian Posted February 2, 2007 Share Posted February 2, 2007 I agree the old 673 should handle your needs. If you are looking for more road speed you could go to a faster rearend or maybe an aux. tranny if you have the room. To me either one of these projects is less work than a engine and or main tranny swap, buy to each his own. If my math is anywhere close to right your truck with the trd 67 and 4.25 ratio rearend at 2100 rpm will top out at about 60 mph with 10.00-20 or 11-22.5 and about 62 to 63 mph with 10.00-22 or 11-24.5 tires Quote Link to comment https://www.bigmacktrucks.com/topic/2097-end-673-with-a-trd67-tranny/#findComment-10229 Share on other sites More sharing options...
Joe Ditchkus Posted February 3, 2007 Share Posted February 3, 2007 I would stay with what you have.If you do not want to rebuild engine you have now 673 Mack's are pretty cheap to buy and not too hard to find.If you want a little more road speed get a triplex with a single overdrive, a double OD sounds good but is too fast and a 673 really does not have enough to pullit very well.60 to 70 MPH is fast enough on a 40 to 50 year old truck. I am sure some will not agree it is only my opinion. Quote Link to comment https://www.bigmacktrucks.com/topic/2097-end-673-with-a-trd67-tranny/#findComment-10239 Share on other sites More sharing options...
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