Good evening everyone. As the titls of this thread shows I will be doing some repairs on a 736 I just bought. It needs some minor paint work but the bigger problem is that it lurches with every revolution of the drivers. I started troubleshooting and found the excentric cranks for the valve rods were installed 180 deg off causing them to bind and bend the linkages. I corrected them and straightened the linkage and it helped but it still lurched. I then removed the shell and placed it on the track with the cover off the worm gear. Running it slow it lurched going forward but not in reverse. What I found are very worn axle bushings for the drivers. I have the bushings on order and plan on modifing a battery terminal puller to remove the drivers. What I am looking for is advice from the old hands on here an any problem areas to watch for and tips on getting her tuned up. I have also noticed about .015 end play on the motor armature. The Greenbergs repair guide says no end play on the 726 armature, is this also true for the 736. Can any one tell me how to tell what year mine was built. It has the diecast rear truck. I think with some work it will make a good looking running unit. Thanks in advance for any help or hints.
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You can make a very satisfactory fix without the trouble of pulling and re-quartering the back two sets of wheels.
The right rear axle bushing is always the one that wears out first(from forward operation), pushing the axle left, the right rear wheel into the frame, and the worm wheel off center.
Use one(or two or as needed) 671M-22 clips/retaining rings and snap them on to the drive axle to the left of the worm wheel. You want to have between half to the full width of a 671M-22 clip of end play in the axle for best performance. Keep the entire gearbox & axle lubed well with a synthetic HP grease(Lucas Red 'N' Tacky #2, eg.).
If you can source some clips with the same inner diameter as the 671M-22, but larger outer diameter, that would be beneficial. The last good tip I heard was to use an appropriate number of plastic bread closure clips(cut to be round) instead of the 671M-22. Very little friction with that method and they too slip right over the axle and stay on.
Rob, The bushings are worn so bad that the drivers not only move side to side but they also move up and down an excessive amount. The flanges are also rubbing on the back of the drivers in front of them. Seems like replacing the bushings is the best way to repair it. Before I tear it down I will try the e-clip trick to see if that helps with the lurching. I noticed that if I run it slow it will bind with the drivers in the same spot every time. I will also run it with the linkage all removed. John,The nubs that you refer to were not engaged in the slots when I got it. I had the motor out and it has no up and down play but does have about .015 end play is that to much? Someone has tried to lube it to get it to run better because everything is full of white grease. Thanks guys.
The bushings are worn so bad that the drivers not only move side to side but they also move up and down an excessive amount. The flanges are also rubbing on the back of the drivers in front of them...
VERY worn. Probably run a long time w/o maintenance.
With all the linkage removed, only the rear drivers are powered.
Also replace the connecting side rods with new ones. They get worn out and the engine will never run smooth no matter what else you do.
If you are going to pull the wheels of, first scribe a line carcass the center of the axle and onto the wheel hub. This will help you get the wheels exactly lined up where they came off and quartering will not be a problem.
Well today I finally got a chance to replace the bushings and side rods on my 736. I marked the axles and drivers and used a modified battery terminal puller to remove the drivers. The replacement bushings had to be reamed after installation as they were a heavy press fit in the chassis. I made a stepped driver to install them to prevent damage. After lube and assembly the engine now runs smooth, no more jumping or lurching even at low speeds.Also now the drivers do not rub against each other. I am glad I took the time to repair it.
Hi - Old 736 is a beautiful engine and I'm glad you got yours fixed. I followed the thread with interest, as I have one myself. No running problems so far, though. Have fun.
Hi - Old 736 is a beautiful engine and I'm glad you got yours fixed. I followed the thread with interest, as I have one myself. No running problems so far, though. Have fun.
I agree, the 736 is my favorite of the postwar engines. Have wanted one for quite some time but just could not bring my self to spend what most were going for. Got this one from a forum member for a price I thought was fair and it came with the 2671W 12 wheel tender also. It looks pretty good considering its age and the fact that it has quite a bit of run time on it. The new bushings cured the rough running and lurching. It now runs very smooth. I scored a late production shell numbered as 779 on e-bay last week very reasonable and I might do some customizing and paint work on it and save the one that came on it. This loco will not be a shelf queen.