VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 I think I fixed it!

A while back I posted about the fuel pump in my 48 causing a heavy engine surge at speed, and, possibly causing my car to jump out of 3rd a lot at speed. Last weekend I took her to a cruise-in that involved about a 40 mile run on I 64. Now, with her new fuel pump, the car had no problem running an indicated 65 there and back, and, never jumped out of 3rd once. Given how easy the car did 65, I'm left wondering if a PO changed the rear gears. I'm really happy with my sweet running 216.

Regards:
Oldengineer

You and I talked about the "bucking and kicking", causing the tranny to pop out of 3rd gear. See the link below.

https://vccachat.org/ubbthreads.php/topics/333464/May_have_fixed_two_problems_wi#Post333464

Looks like you can stamp this problem, as "case successfully closed".

Congrats on your smooth running 216.

Thanks: I've fought this problem for 3 years, along, with some other issues with the engine. It's all kind of come together now. On the cruise-in trip the car hit 70 briefly a couple of times. I'm wondering what the top end of these cars really was back in the day. Hopefully my experience solving this will help others.

Regards:
Oldengineer

When I was in high school my 47 would top out at 82 mph, never did blow it up.

The 1941-1947's would do between 80 and 85 MPH on the speedometer.
The 1948 and up 216 with a 4.11 between 85 and 90.

I guess I should push my 48,I've never done those speeds

Probably just as well not to try it with a engine over 65 years old.

Back in the day - 40 years ago - I had a girl friend in Superior, Wi.
We went up to visit her mother - drove 55 to 60 mph - without the knowledge that perhaps this was a little too much for a 216 1947 Chevrolet.
We were late in leaving Superior to get back to college in Mpls. and drove 65 to 70 miles per hour home on old 35 running through Wisconsin. The speed was way to fast but the thing that scared us even more were all the deer we had to dodge to get back to school so we did not break curfew.
With the 1947 I have now I would not think of driving that fast. The things we used to do when we didn't have a lot of sense.

Back then, we were INVINCIBLE !

I think the lesson learned here is to not discount any scenario, even though the logic may not appear to be there.

No one would "logically" believe that a fuel pump could ultimately cause a tranny problem. But it did, in a round about, sort of way.

Car concerns are like a good murder mystery. The "who dun it" may not be so obvious.

If you wonder if the P.O. changed the gears, pull the differential cover, check for stampings on the pinion gear, or ring gear, possibly.

37/9 = 4:11.
39/11 = 3:55.

If no stamping, count teeth on ring and pinion.

A good time to change fluid, as well.

Mark a tire push car one reveloution of the tire (wheel) and have some one watch and see how many times the balancer turn over. Slightly more than 4 times = 4.11, slightly less, 3.73.

Better specify what gear the tranny will be in, when this procedure is performed.

That sounds like a good idea.... third or high gear.

Bob:
From my experience in solving the gear jumping problem, an issue( bad engine mounts, slop in shift linkage, engine surging, etc.)that causes the engine and transmission to move/rock excessively can cause gear jumping because of the resulting movement of the gear shift levers at the bottom of the steering column. That's why, as implausible as it seems, replacing my bad fuel pump seems to be the final piece of the puzzle.

Regards:
Oldengineer

YOU know O.E., it is always good when an "out of ordinary" problem is solved ...... with an easier fix, than imagined.

One lays in bed at night, thinking it all through, just knowing the tranny has to be overhauled, but the GODS then shine down on you and say , naw, just replace the fuel pump.

Makes for a happy ending.

Bob:

You're right. I had just about decided to open the tranny and replace the shifter forks and detent springs and balls. I acquired a extra shifter assembly last Summer just in case.

Regards:
OLdengineer

When you think of the problem, the "bucking and kicking" could certainly knock the tranny out of gear ... much like a bucking bronco.

Getting to the source of the bronco could have been an ongoing issue, but you got it figured out.

Makes the smooooth ride today, even more smooooth.

Something about that self satisfaction, when it all turns out well.

Bob:
I like your bronco analogy. When I first bought the 48, it was missing the two mounts on the sides of the bell housing. It was the hardest car to get going smoothly from a stop that I ever drove - loved to buck and bounce. Then when I finally got her in third on the highway she'd hop out of gear every couple of minutes. Way more fun to drive now. I appreciate all the help and advice I got off the folks on this forum.

Regards:
Oldengineer

If we wait long enough, you just know a new chapter of needed diagnosis will open up.

Bob:

I agree - These cars with the torque tube drives are interesting to diagnose and fix. There will others who run into the same problems I did.

Regards:
Oldengineer