The Stovebolt Site Forums The Shop Area Engine Shop ’59 3100 283

Hi:
I recently purchased a 1959 Chev 3100 Apache with a 283 engine. It also has the GM overdrive accessory which appealed to me. The truck interior and exterior were in excellent condition, but the engine was very tired, so I had an expert mechanic with small block experience rebuild it. This included a four-inch bore (because 0.40 over wasn’t enough), a new stock cam and new Offenhauser heads. As a result, the engine is now a 302 and the truck is a screaming sleeper.

In addition to rebuilding the engine, I had a new clutch, pressure plate, throw out and pilot bearings installed. And the flywheel was resurfaced. I also had the driveline rebuilt and balanced.

After all this engine work was done, I fired up the truck and took it for a test drive. As I said, the engine was exceptionally strong, but something was wrong with the clutch, pressure plate, etc. At least I thought that was the problem. In first gear, as I let out the clutch, the truck shuttered (chattered) violently. It was virtually un-drivable. I could, however, start off in second gear with no problem, including the transmission automatically shifting into OD after reaching 30 mph and letting off the accelerator pedal. It also shifted well from second OD to third and third OD. There was some chatter in reverse, but not nearly as bad as in first. I drove it around this way for awhile, thinking it needed to be broken in. No such luck. Every time I tried to start off in first gear, severe shutter/chatter.

So, we initially thought it was a clutch, pressure plate, flywheel problem. However, after disassembling everything, there were no visible issues that would cause a “chatter/shutter” problem. No grease/oil on the surface of any parts. Everything was aligned properly, no “hot spots” on the disk, etc. Rather that put the new parts back in, I had the mechanic install a second new set of clutch/pressure plate/throw out/pilot bearings. After everything was installed again, we fired up the truck and tried to start off in first gear and the same thing happened – severe shutter/chatter. But starting in second, etc. was fine.

At this point, we started to seriously think about what else could be the problem. About the only other things we could think about were the rear engine mounts which we didn’t replace because they looked o.k. (the front mounts were replaced with the rebuild), and maybe the lack of a cross member to support the transmission area (which looked a little weak and susceptible to shaking).

So, while we haven’t installed the new rear engine mounts yet (or another cross member to shore up the transmission area), I’m doubtful we’ve diagnosed the problem. We will install the rear mounts this week. Does anyone have any experience or suggestions with this severe “shaking/chattering” problem on “second series” trucks?

Does the shuddering go away as you accelerate in first gear before shifting into second gear?

Normally clutch shudder is caused by an oil contaminated clutch, clutch linkage, etc. but assuming you've verified that everything is installed correctly and the parts are correct, and there's no oil on the clutch, you have to look elsewhere.

Loose bell housing, bad motor mounts , or even a broken or improperly adjusted clutch linkage could be the culprit.

Also check that your carburetor is adjusted properly and functioning properly. Low rpm or incorrect fuel/air mixture at idle might make the engine vibrate and stutter.

Is the transmission mount new?

Get someone to observe the situation when you take off in first. Leave the hood open and have him watch the engine and trans when you take off in first. Have him lay on the ground and try to look under the truck to see if anything is shaking or coming loose.

What transmission do you have? If it is an SM420 (which would have been the stock manual) the first gear is extremely low and feels weird to start in compared to a more modern vehicle.

Roughly where in California are you?

First and rev are low gear ratio. The most "load" on clutch and etc. Don't know what trans you have yet. Four speed with granny low?

1. If four speed, you don't use first to "accerlerate". You ALWAYS start out in second. Never in 1st (compound low) except to crawl or pull a stump. 1-5 MPH range.
2. If four speed, it is cantilever mounted off of bell housing. Assume the crossmember you speak of is for a truck bell housing side pad mounting. Pretty easy to inspect that crossmember/rubber pads for loose. You can call those bell housing mounts "rear engine mounts" or other names.
3. If you agree with 1 and 2, and still have shutter, it can be a bad clutch repacement job, bad ujoint replacement job. Possible just needs adjustment.
4. Maybe you have a column shift?...or a non original trans.

We do need a little more info as to exact equipment. And many pics for us to pick up what may be wrong from our house.

The fix for that is to put it in 3rd, and rev the engine up and sort of slip and burn the clutch in a few times, only 3 to 4 seconds or so. See how much ______ I get for this!
And wow a bunch of work for no reason taking it out.

"Looks good" is not a suitable test of motor mount condition. Since you've already stated you've got a SM-319 overdrive transmission, ignore all the advice about the 4 speed having a low granny gear- - - -it doesn't apply to your situation. Try this as a quick diagnosis procedure- - - -NOT a permanent fix- - - - -attach a cable come-along between the driver's side frame rail and the exhaust manifold, and put a little tension on it- - - -not a great deal, just enough to keep the engine from rocking back and forth as you accelerate. If that eliminates or seriously reduces the shudder, change ALL the motor mounts, front and rear. There's no need to add a rear crossmember that the factory didn't install in the first place. Good luck!
Jerry

Thank you for the quick replies. Couple of quick answers: the transmission is a three speed on the column and is the Borg Warner R-10 type (the serial numbers on the trans start with “GM” so my assumption is that GM had the rights to use/sell the BW product/design under the GM brand). The severe shudder/chatter does not get better as the clutch is released – if anything, it gets worse to the point where you have to quickly push the peddle back in or kill the engine and shutter to a stop. The shudder/chatter is so bad it feels like the entire engine/trans/drive line is going to fall apart. First gear is low, but it’s not as low as the typical “granny gear” in a stock four speed Advance Design truck (I’ve owned one before).

As I mentioned, we did replace the front engine mounts, but did not change the rear because they looked o.k. We will change the rear mounts this week, but that sounds so simplistic to fix something so severe as what I’m experiencing that I have my doubts that will fix the problem. Hopefully, I’m wrong. I’ve ordered two different sets because they’re cheap and I want to see the quality before installing them: one from “The Truck Shop” in Orange, CA and another set from “The Filling Station” in Oregon. I live in San Jose, CA and this is my third ‘50s/‘60s Chevrolet truck (I’ve also owned a stock five window’52 and a ‘53 Suburban which I converted into a resto-mod with a 350 engine and trans and a Camaro front clip.

As far as the adding another cross member, that thought came after working under the truck and looking at how weak the current set up was. There’s approximately three feet between the cross member from the engine to the transmission. One of the techs at The Filling Station said he thought this was a known design flaw in the “second series” trucks.

Finally, the idea of opening the hood and observing what’s happening while the truck is shuddering (and purposely trying to get it to shudder), we tried that too and it looks like the engine moves at least 1/2 inch forward and backward (rather than a normal running engine slightly moving side to side). That’s what prompted the idea that it could be a rear motor mount problem and/or cross member.

I think you've found it.

Do not add another rear mount to the transmission. 55 through 72 trucks all used the four mount system, two front or side mounts
and two mounts on the bellhousing regardless of the transmission used and they work fine.
I just recently did an engine swap in a 55 3100.
The rear mounts were mush, had the wrong bolts, and didn't have the internal support sleeves.
Yours may have a similar problem.
Fred

I'm curious as to why the shop didnt test drive it and fix this issue before letting you have it back. It is obvious enough that they should have caught it and then fixed it. Just my 2 cents.

The rubber grommets in those bellhousing mounts can indeed turn into jelly-like rubber and be very unstable.


Got any pics of all the mounts ?

Hays On one of my rat-mobiles oil has melted thosr rear mounts,51 1/2 ton till the core steel of tthe mount is showing. It doesn't chatter,I pulled tree limbs out of the yard no chatter. I guess you could do that old circle track trick of chaining the left exhaust manifold to the frame to see if that would tell you anything. That is a rude way of testing this problem,it would cause the circle car to carry the left front wheel up off of the track. Stupid thing to do but might help you locate the trouble. Good Luck !!