M38A1 won't drive over 35 MPH... Help!

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tnbender

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Hey. I'm restoring a 52 m38a1 and lack knowledge with the mechanical aspect of it. I drove it to a local welder to install panels I bought and its top speed was around 35. At this speed, it shook really badly. Someone suggested that It was because 4x4 was engaged, but I do not believe it was. Has anyone else experienced this problem, or do you possibly know what the problem may be and what could restrict the speed on my vehicle? Thanks!
 

Lifer

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RE: M38A1 won

Sure sounds llike it was in 4-wheel low. The shaking could be due to bad steering components, out-of-round tires, or bent wheel rims. If you had a lot of vibration, you ought to check all your u-joints and transfer case bearings.
 

acetomatoco

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RE: M38A1 won

bellcrank in steering and out of balance front tires... Spend the money and get the manuals and read them in bed for a coupla weeks.. Should go 55....ACE
 

jimk

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RE: M38A1 won

Shut it off ,put it in any gear, jack up one front wheel. If you can't turn the wheel it's in 4WD (or the brakes drag bad). Tires may get a flat spot if it sits a while. Make sure it is running on all 4 cyl. Make sure the throttle opens all the way(at carb) w/foot on the floor. Make sure the brakes aren't dragging by giving it a push on a hard level surface. JimK
 

Ferroequinologist

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Mine won't go over 35 either, well, it doesn't have a speedo so I don't even know if I'm getting close to 35. It does seem like it. But unlike tnbender, I know the problem, it won't go into 3rd gear! Any suggestions on that one? Sorry if I'm hyjacking a thread.

I know it sounds stupid, but did you check the parking brake? It might be draging. (I'm all about everything brakes now):oops:
 

jimk

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Most likely to least-adjust linkage,worn linkage/shifter,bent shift fork,rusty fork shaft,mainshaft pilot bearing gone,gear frag'd.JimK
 

Stretch44875

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This jeep had the same problem, anything over 35 mph and it would shimmy like crazy. No idea what the problem was, with 5.38 gears, getting to 35 was hard enough.

Dennis
 

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acetomatoco

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It was your bellcrank, air pressure and balance of wheels and shim packs drag on kingpins... all civvy jeeps and all Mil Jeeps have had the problem one time or another.... Shaking so bad you do not want to go any faster.... The ebrake dragging on the A1 is not a problem cuz it couldn't stop or hold a kids scooter... The linkage and shoes are like a miniature deuce version which is also a poor set up... The band type like the MB or the two shoe internal expanding like the M38 or the winch band type like the M151 were surefooted....mucho better.... There is a list of about 8 items in the manuals for the jeeps in descending order of importance to combat shimmy... some folks break down and put on a steering stabilizer to mask the problem... Don;t forget to set the drag on your steering box in the straight ahead position... ok enough clues.. get to work... ACE
 

FrankUSMC

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Get the manuals. I had a very nice M38A1, that was sloooooow, and hard to start. I took it to my friend (retired Marine 30 plus years, joined June 1941), he told me the problem right away and he was right. My timing was out 180 decrees! He fixed it that day, after that she ran great and started so easy....so I sold her.
One of the few, Frank
 

tnbender

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Thanks for your response on my M38a1.

I drove it to my uncles house saturday. He checked it out for me and messed with the carb. and the timing and things. He is no mechanic, but does know a little. He then stated that there was a problem with the cylinder closest to the radiator. When he messed with the spark plug, he stated "that it was trying to fire". (It was a little corroded) After listening closely, it sounds like with each rotation of the engine, there is a banging sound of metal hitting the ?Valve cover? (not sure if that is the term for the cover on the very top of the engine). So, I think all 4 cylinders not running may be the problem. Im 21 and I know NOTHING about cars or engines. Before I bought my jeep, I couldn't even change my oil! So knowing these facts, is there anything else that you might could suggest regarding what this problem may be, and what may need to be done at this point? THANKS SO MUCH!
 
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