'73 T-All 345/727 auto 'bucking' on first highway road test

W

WagnMastr

Member
Hey, gang.
Last weekend I thought I would finally take my '73 Travelall that I recently put a built 345 into, meshed up against a 727 auto (on which I adjusted the bands after putting in the engine) on its first highway road test.
I was pulling off the exit after 10 miles to head back home and I got a single 'bucking' feel. Thinking I might have just left off the gas real fast and it might be more of just a one shot deal, I turned around and got back on the highway and had the bucking going on non-stop. I made it home, but there was a lot of bucking, keeping it under 40mph or slower, backing off the gas completely, then picking it back up again.
Tranny fluid isn't leaking, and it is at proper amounts.
The engine never stalled, so I don't know that it was the cause, but I cannot rule that out. I guess it could be points or spark plug wire arcing?
Maybe torque converter going?
Maybe bad fuel?

Once the bucking started, it did it from speeds of 60 down to 10 mph, so it was in all ranges, all gears.

Any thoughts here?
 
Last edited:
Hey, help us understand the "bucking." is the engine cutting out, or are you describing a tranny problem? I have had a wire going to the + side of the coil break inside the insulation. The wire looked fine from the outside, and it would cause the engine to die intermittently when I went over bumps. It was a total tail chase for a few days until it stopped completely.
There are a bunch of things that could describe your condition. This is only one example, so help us better understand what we are talking about here.
 
The engine doesn't seem to be cutting out in that it it stalls and I have to turn the key again. However, it sound like it could be cutting off due to fuel delivery, but I had the same issue whether or not my electric fuel pump was on. The fuel filter is new and clear of any debris.
I just drove it moments ago and after 3-4 minutes, it happened. It bucked a few times, the speed dropped even when I retained the same pedal pressure. Then it picks back up and bucks, slows down and bucks some at lower speeds, too.

I am going to change the points/condenser/rotor/cap and plug wires since that is the only thing I left untouched when I put in the engine a couple months ago.
 
Last edited:
What you describe is not an issue I've ever encountered with any 727 tranny malcolm!

What ya do have going on I feel is a dead miss coming and going on the engine side.

If...the issue is fuel-related, then there is a problem(s) with the fuel pickup system in the fuel tank(s). I'd concentrate on using only the rear tank and start there. It's easy to pull the fuel sender out on that one to check every thing, I bet ya find out that the pickup tube in the sender is partially clogged.

The "difference" in a misfire caused by the fuel system and one caused by an ignition issue is very hard to determine most of the time. But a clue is...if the "miss" occurs instantly, then ya home in on ignition. A fuel-related miss normally comes and goes in a more random form.

Back to the transmission though...has the work you have done on the tranny seem to have cured the slow initial engagement of the transmission in drive?
 
It did appear to make the tranny shift nicely enough and engage very quickly into drive, and I adjusted the kickdown enough to where it shifts at 15-20 into 2nd and 35-40 to 3rd under gradual acceleration. Those were great notes on the band adjustments and real easy to do.
Tomorrow, I am picking up a brass contact dist cap, new rotor, points and condenser to eliminate those as part of the issue. Plug wires, too.
I am using the passenger tank right now just because the fuel had a shorter distance to travel and less chance of plugged lines. Haven't refilled the driver side yet, though will do so down the road. Can't wait to empty both tanks and go to the pump to fill 'em! Can you say cha-ching?

Hey, mm, you did get my package and $$, right?
 
Yeah, I did get your package, I forgot to let ya know. My lack of following up has become more prone recently, sorry!

Since you are running the front task, then simply disconnect the line and blow with compressed air back through the system and see what happens. It will most likely dislodge any debris temporarily but it will come back soon enough.

Good news on the transmission service work, one more issue that's is handled now!
 
I hooked up my 6 gal boat tank and ran it 20 minutes or so without issue, so the bucking problem stemmed from fuel delivery. I hooked up my driver side tank, threw in some new fuel and drove it a half hour on two occasions. Again, without issue. So, the passenger tank, though I had used it some without the bucking happening, must be getting crap up into the line.
I did blow out both the driver and passenger side lines for good measure (before even hooking up the driver) so that should help.
 
You must log in or register to reply here.
Back
Top