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Imp c4 is popping out of 3rd

AKdadio

AKdadio

New member
Have '74 Imp, new to me. It seems to run fine in 1,2 and 4 on the differential but when I try 3rd it pops out. I have not pulled the plate(s) on the OC4 to take a looksie but I am wondering if it would be a shifting fork problem. ANY IDEAS? Thanks.
 
Do you have a parts and maintenance manual for the Imp? If not, contact Bill Guthrie at SnoTrans and he may be able to copy a manual for your Imp and send it to you. The manual will be helpful to determine where to begin. I sold my Imp several years ago. I should of made a copy of the manual to use as reference but did not think about a copy at that time.

I never had to do anything to the rear end/transmisson of my Imp except change the oil as the machine only had a total of about 475 hours on it. Make sure if you change oil or add to it that you use product that is compatible with the brake band steering in the OC4. The most common is 10W HD hydraulic oil. I used Aeroshell 100 mineral or a good quality 10W hydraulic tractor fluid. Don't use heavy gear oil or you will have difficulty steering. You do not want to glaze up the brake/steering bands.

Good luck on solving the shifter problem.
 
Thanks Mtntopper for the tips on oil. I do have a manual - fortunately. It says it is for a Clark "s70f " or something like that, but comparing pictures with my C4 it looks like the same thing. Cheers.
 
You could talk to Bill or give Peterson's Equipment a call too. They have a lot of experience with the Imp's differential. The transmission is the front half of the differential and the steering in the back half. I would bet that they could give you an idea on what to check. If you call Peterson's, ask for Steve. He runs the show and knows more than anyone I've ever met on the C-4. :tiphat:
 
Thanks for the direction. Nutsster- nice rig! Wife says we need to go get a spiffy new paint job- If she saw yours she would really nudge me.
 
After taking my C4 apart for inspection (and just to see how it works) I have a pretty good understanding of the operation of the different systems inside. Since the gears are all straight cut, there should not be alot of side force pushing them "out of gear". The shifting fork mechanisms utilize a retaining ball system that hold the forks in place. this works much like a rachet wrench holds sockets on. I would say that one of the retaining balls is probly stuck or one of the shifter fork shafts has come loose. Pull the side plate off (shifter forks are all attached to this) and take a look at what's going on. Make sure to first pull the shifter shaft out the top of the gear case. Should be a simple fix for you.

John
 
John, I haven't pulled the cover yet but that is exactly where I was goint to start. Have never seen the inards first hand so it will be new. If you catch this post in time (before I proceed). . . is there anything that wants to pop out at you (and disappear), spring loaded, whatever, that will be a factor when I pull it apart?
 
Nothing to be afraid of in there. Just make sure you have the shifter pulled out the top first. It is held in with a heavy retaining ring. Walk the ring out the notch with a couple screw drivers, use one as a sorta ramp and use the other one to tap the ring around. Once this is out pull the side cover and your in. Once you have the cover off call me if you want me to explain how it works to you. Do you have diagram?
 
Teeoster said:
Do you have diagram?
Click to expand...
John, can you post some photos and the diagram here so we can see what you are talking about? I'm only vaguely familiar with the OC4 but would love to learn more. I'm sure people who actually have OC4s would benefit even more than I will if you can post some photos.
 
MtnCrawler already posted these for us when I was working on my Brake linings. Here is the topic. "C-4 Schematic changing brake linings" Last post was in October.
 
Ok,

Here is a exploded view that Mtncrawler sent me.
 

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One last one, again these were all compliments of Mntcrawler a few months ago
 

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Boy! That thing looks a lot like the Clark/Funk transmission in my Kristi KT4.
I hope it is, cause then you guys just made my job a lot easier .:cool2:
 
Thanks to Teeoster, you have actually answered one of my questions, which was whether the "S70F-12" was actually a C4. I am fortunate to have the diagram and parts list but was a little concerned because it makes no mention of c4, just the S70F-12. It will probably be at least a week before I get a chance to investigate, but I will post my findings in case anyone else can benefit. And, if I run into trouble I will take you up on a discussion. . . . will let you know. Thanks for putting in the effort to post the details!
 
Re: Imp c4 is popping out of 3rd (UPDATE)

Okay, need some advice. It appears I am not able to fully engage the diff in 3rd because the shifting mechanism is hitting the frame. There are a set of adjustment set-screws that allow th shifter assemble to move- I have already moved it to where is is bottomed out but the shifter still hits the frame (see photos). Any clever ideas out there?
 

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Do you have the ability to cut and weld metal?

It does not appear that you can easily relocate the shifter mechanism (even if only a couple of inches).

It strikes me that one possible solution would be to weld a new cross brace into place (the piece your index finger is resting on). The new piece could be welded right next to the existing piece (even welded to the existing piece). But then you would cut out a small part of the existing piece where the shifter is coming into contact with the cross brace.

Do you think that would work? Seems like it would, based on the phots.
 
Welding is not something I have learned- but should. Your idea would work, weld-shop could do it in a jiffy. Here is another idea I considered last night: Remove the shifter-lever from the diff and bend it toward the front- just a 1/4" to 1/2". That would give me back the room to shift. Is there a problem with that idea? - Kelly
 
I think the key to your success is that the shift lever must whatever it is connected to FAR ENOUGH to get it into 3rd gear and keep it there. If bending the lever would do that, then that is a good solution.

Worst case is that you bend it, it does not work, and you bend it back.

Best case is that you bend it, it works, and you drink a beer!
 
Just use a BFH to move some of the metal around:) just kidding, I think you could easily shorten the long shift linkage (pipe) by 3/4 of an inch and get close enough to use the adjuster screws again.

I would look into why the system changed. could have a bad transaxle mount of something ? ?

John
 
You might have some wear where the shifting tube slips over the ball topped piece comming out of the transmission. Or you might have a bent shifting fork inside. I don't know about the Imp offhand but the A- Sprytes are hard on the front diff/transmisssion mount and bolts so look at that too. And if there is any cracking going on with the tunnel you might be getting enough flex to pull it out of gear. I think credit goes to Mtntopper for the manual pictures
 
Yes, farther is what I need, had an off-thread reply to use a hammer and see if I can tweek the shift linkage (which is welded pipe) to buy more throw. I will report back. Thanks.
 
Mtncrawler- thanks for ideas, I haven't had a chance to dig into it again but will post my findings. . . it still works great in other gears. . .

"look mom, no hands . . . "
 

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I have not even looked at the linkage issue since the original posts. Still need to disconnect linkage and drive around for a while in 3rd to make sure I can blame the linkage. The idea about threading is interesting- there is already some adjustment built in at the front end- just need to shorten it a tad. Thanks for the ideas. Am moving and have not a chance to do anything with the cat :(
 
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