Topic: Grinding gears


47Jack    -- 09-19-2010 @ 7:25 PM
  Hi Guys..I finally got to drive my 47 1 and a 1/2 ton truck on the road. I know these transmissions didn't have syncros but what's the secret to shifting without grinding. I've been double clutching and trying to get the engine rpms low, which helps but I'm still grinding. This is a four speed. 2nd to third is the worst and sometimes I get it into fourth smoothly.

After I got the distributor going my next problem was a collapesed gas line and now I just ordered a rebuild kit for the carb.

Thanks in advance for any info.
Jack


1932BB    -- 09-20-2010 @ 7:56 AM
  Double check your clutch adjustment to make sure the clutch is releasing. As you stated, a low idle speed also helps. Shifting the big transmission well is an art. Some skilled individuals can speed shift it. In my experience it seems that the more people that are watching/listening, the more spectacular the grind. My wife doesn't double clutch the 32BB, just waits in nuetral with the clutch in until everything winds down. I double clutch and sometimes I hit 'em and sometimes I don't. Sure get a grin when it happens right!


alanwoodieman    -- 09-20-2010 @ 7:58 AM
  it can be fun learning to double clutch, old truckers' really earned their keep-lousy brakes and straight cut transmission gears. It is realy a matter of timing,I just sort of blip the gas pedal during the change and this seems to help, I have tried letting the rpms die down but that does'nt seem to work. I have found that if I don't think about it and just do it, I am better able to shift the gears. Good luck!


supereal    -- 09-20-2010 @ 10:00 AM
  Ah, yes. We had a couple of these straight cut gear boxes, and the trick to smooth "double clutching" is matching the speed of the engine with the speed of the vehicle. Shifting down to a lower gear, you need to increase engine speed, and shifting up, take enough time for the cluster to slow, both when in neutral as you first engage the clutch during the double. It is more of an art than a science. Using heavy oil, such as 140, in the transmission often helps. We had one truck with a "brownie" auxiliary, and "split shifting" meant steering with a knee while working the levers.


Stroker    -- 09-20-2010 @ 2:27 PM
  As all the "old timers" have noted, shifting is an art, not a science. I grew up driving a 29,31,35,40,41&42 ton-and-a-half trucks. Each one was different, even though the 40 through 42 all had identical 4-speed "crash boxes". It's like each one had a personality of its own. I probably spent the most time driving the 40 over the road, and it liked to be rev'ed up quite a bit before
shifting to the next gear. So.., I'd wind her up in "grandma", push the clutch in, put it in neutral and let the clutch out. Next, I'd put the clutch in, and quickly put in 2nd. etc.
Down shifting requires bringing the next lower gear "up to speed", so the process is to de-clutch,
put it in neutral, let the clutch back out while rev-ing the engine to match the new lower gear,
and then then de-clutching to shift down.

It's all about learning what your particular combination "likes". Once you develop the touch, you'll be shifting like you had a Porsche. When you do it every day, it becomes second nature.
If I were to hop in the 40 today, I'd have to learn all over.


47Jack    -- 09-20-2010 @ 5:00 PM
  Thanks for all the good advice. I thought you guys were going to tell me the transmission was bad. I will get a feel for it. I have double clutched it but I'll pay more attention to engine rpms.

Jack


f1ford48    -- 10-03-2010 @ 9:16 PM
  as stroker said each one of his trucks was different- the reason was each one had a different rear end ratio. the secret to double clutching these trannys is matching the engine rpm to the rear end rpm.usually on the upshift just a quick double clutch is required. downshifting requires you to get the revs up to slide into that lower gear.
the 48 truck owners manual actually has instructions on shifting the 4 speed ''spur gear'' transmissions.
to avoid those standstil grinds from neutrel to first or reverse I usually start up in gear with clutch depressed and select my startoff gear from there -grind free!



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