Third gear problem

[huntman2]

I have an 80 CJ7 with a AMC 258 i6 / 4.2l engine. I am not sure about the 4 speed Transmission but I think it is stock. My problem is the third gear. It runs fine in reverse, first and second but begins to buck and miss when I hit third gear. Anyone have any idea what is causing this?

 

[JR74CJ5]

Are you saying the motor starts missing and "bucking"... like shaking?

From that i would assume 2 possibilities first:

Vacuum leek, or issue
or
Possibly Motor mount, but i would think that would be all the time so maybe not...

The motor mount easy to check, (you probably know already...) while running hit the accelerator from under hood with parking brake or block on tires and see if engine lifts and slams hard... Or buddy hit gas while you watch etc...

Vacuum, not so much, but start looking around...

If you mean Tranny is rough and either popping out of gear etc, not sure what tranny you have, but may be syncro's..

Other possibilities,
Carb
Timing
fuel filter / pump

More info would probably get a better response from more knowledgeable peeps here...

Like higher RPM's or are you able to get to same RPM's in fist / second with no problems, Distributor / Carb / Tranny types etc...

Again I'm pretty new, just thought id share where i'd start...


~ JR

 

[huntman2]

Thanks I will start to look around. I am not much of a mechanic so I probably shouldn't own a jeep. I am going to use it on a deer lease and it will never be on the road. I cannot get any info from previous owner regarding the Transmission , carb etc. The best way to describe what happens in third gear is that the motor bogs down and almost dies. The rpm's in 1st and 2nd are equivilent to what i had when I went into 3rd. I think you might have hit it when you suggested timing. I does go into 3rd gear OK. No grinding or kicking back. It just acts like it wants to roll over and die.. I think I have a Dana 20 Transmission and a Dana 300 Transfer Case . Everything appears to be stock on it.

 

[JR74CJ5]

Thanks I will start to look around. I am not much of a mechanic so I probably shouldn't own a jeep.

Nawwww... After a little research and getting hands dirty you'll start to get it man... These things are so easy to work on compared to a new vehicle... Get a factory service manual and you'll damb near be a mechanic on these things...

I am going to use it on a deer lease and it will never be on the road.

You can get rid of smog then... although not entirely necessary, it helps make thing simpler when done...

I cannot get any info from previous owner regarding the Transmission , carb etc.

Take some pics to look side by side on the identification posts/threads here on this site... should help you narrow down. Then if still not sure post the pics requesting someone help, also look up vin number i think it will narrow down the original stock stuff to try to match to see if still the same.

The best way to describe what happens in third gear is that the motor bogs down and almost dies. The rpm's in 1st and 2nd are equivilent to what i had when I went into 3rd. I think you might have hit it when you suggested timing. I does go into 3rd gear OK. No grinding or kicking back. It just acts like it wants to roll over and die..

This sounds for sure like a vacuum or timing issue. Post a pic of your distributor, so we can all see what type to start digging into that... In mean time check for vacuum leaks.

I think I have a Dana 20 Transmission and a Dana 300 Transfer Case . Everything appears to be stock on it.

Dana 20 is Transfer Case and so is Dana 300 ... I'm not sure about the 80's... You said 4 speed, (R,1,2,3,4) if so (someone correct me please if wrong...) maybe a T-18 (is first gear stupid low... can't get very far with it? like a granny low?) If you meant 3 speed (R,1,2,3) probably the T-150 .

Here is a very good info site: Novak Jeep Conversions - Home

(That site can also help with Transfer Case info too... Usually the top result on google search: for instance google "Dana 20 " or "Dana 300 " and the Novak info page should be on top of listings...)

Here are links to the two type of tranny i assume you have, but again please remember i am not very expert status (yet) So I am hoping someone will either say 2nd'ed ^ or whoa JR way wrong...
T-18 : The Borg-Warner T18 & T19 Transmissions - Novak Conversions
T-150 : The Borg Warner T150 Jeep Transmission - Novak Conversions

With that in mind, I hope I've helped you out a little... Post some pics of that distributor...

Cheers

~ JR

 

[Old Dog]

You should have the Dana 300 Transfer Case .
since you just got the jeep I would change the fuel, and air filter if you haven't already. Shoot maybe even do a compleat tune-up.