Inside the 4+3

[corvette66]

Yesterday i took out my transmission. Easy, not much to it. So if you read my previous post "smoken!" about my overdrive unit, you know i thought i smoked it to bits. Well today I took the overdrive unit apart. Was also a real easy job. All comes apart in about 3 pieces. (Can't undersatnd why they charge so much to do these repairs) I figured my clutches or springs were bad, wich would not give me the presure needed to run the OD. Well the clutches look fine, and the springs don't look "colapsed" as one told me can happen. I figured the clutches would be all worn loking and smooth with no friction surface. They look good to me. Bearing all look good as well. Actually..nothing looks worn at all. ?????

So i was wondering if maybe it isn't the overdrive inner workings. maybe it was a fluid problem??? It was full. But when i disconected the transmission cooler lines, the lines just dripped a little bit. They didn't look to be filled. But the OD was full with fluid. Wonder if there are any other possible problems that would cause my OD to not work. i'll fill you in on whats go'n on if you didn't read my last post.

When I would click the OD button, the light would come on, and my car would drop RPM as usual, just not as quick, also wouldn't drop as far. for EX at 1600 RPM i click the switch and it would normally drop to around 1200, but with the bad OD it would drop to about 1450 RPM. That was only if i was not on the gas. If i step on the gas after pushing the OD button, the engine would rev up like as if it was slipping. (reason i thought it was clutches)

So now i don't know....???

dan

 

[unleadedbrew]

That's the same thing I've been asking, '66'. Why the high rates? I got a quote for 2900.00 just to do the manual portion. Wonder if it just has to do with the name? You know Corvette, Rolls, Bentley, Lambo, etc. :eyerole

 

[Ken]

Do yourself a favor Dan, and read through some of what Paul has to say about 4+3 PROBLEM OVERVIEW

This page will give you some in depth views into the problems associated with Doug Nash Overdrive units used in 1984 to 1988 Corvettes. Since many shops have little or no experience in dealing with this odd ball gearbox the images will show you what has happened inside, the cause, and the proper repair procedure. It is my intention that by sharing my 15 years of knowledge in rebuilding overdrives, more people will understand its function as well as become more educated. The new knowledge gained will hopefully make you repair them correctly or help make the proper repair decision. I've personally rebuilt an average of 120 overdrives a year for the past 15 years. We have shipped them globally to individuals and GM Dealerships. We have also become a vendor for General Motors and continue to make and sell parts for this particular transmission. In that same time frame we have only seen about 3 percent of our units come back to us in that 15 year span.

We continue do redesign component parts for the overdrive and pick up where General Motors and Doug Nash left off.

 

[JonM]

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[corvette66]

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Well I just got in, I put the OD unit back together till i get the new parts. I take it this is where the labor charges come from. It was a bit tricky, but yet not $2900 tricky haha. I found similar prices as well UNLEADEDBREW.

I found that on 5speeds.com (which ken also sent) I learned of this site about 2 weeks ago. They have the soft rebuild kit which includes clutches, seals, filter, gaskets, and some other wearable parts for only $95.00. So 95 bucks and about 8 hours of work gets me what others spend 3 grand on.

Nice work jon, i love that black rose. I have my car all ripped up and starting to sand it now. im probably going to go with the original black/silver, but i thought about the black rose after i saw your car pics a few weeks ago. Looks great.
How did you get the door off? with all the wires? will the wires and harnesses slip out of that rubber tube on the side of the door?

 

[JonM]

Nice work jon, i love that black rose. I have my car all ripped up and starting to sand it now. im probably going to go with the original black/silver, but i thought about the black rose after i saw your car pics a few weeks ago. Looks great.
How did you get the door off? with all the wires? will the wires and harnesses slip out of that rubber tube on the side of the door?

Yes...everything unplugs and slips (using poetic license with the word slips) out of the boot. What I also did was cut the wires and put some waterproof connectors on switches installed on the door panel. In this manner it’s easy to just unplug the wires if I need to remove the panel in the future.

 

[corvette66]

sounds good, I was wondering how i was goingto get the aluminum panel out, that is in the door. looks like it is in there pretty good. With it in the way I couldn't get at the wires. But that metal panel should slide out some how.

 

[JonM]

sounds good, I was wondering how i was goingto get the aluminum panel out, that is in the door. looks like it is in there pretty good. With it in the way I couldn't get at the wires. But that metal panel should slide out some how.

Here is an artical about changing the window regulator...it should assist you

http://www.corvettemagazine.com/2000/december/window/windowpg1.asp

 

[8388]

When I would click the OD button, the light would come on, and my car would drop RPM as usual, just not as quick, also wouldn't drop as far. for EX at 1600 RPM i click the switch and it would normally drop to around 1200, but with the bad OD it would drop to about 1450 RPM. That was only if i was not on the gas. If i step on the gas after pushing the OD button, the engine would rev up like as if it was slipping. (reason i thought it was clutches)

So now i don't know....???

dan

You might want to take the valve body apart. Sometimes and it doesn't take much, debree can get in there and keep the pistons from moving freely. There are a couple of check balls, so be carefull when taking it apart.

Also note that inside the OD unit there are 2 sets of steels and clutches. One set for the driven and the other for the over drive. If your fliud was not burnt, and you saw no abnormal amounts of debree in the pan, chances are cleaning the valve body and adding the proper amount of fluid and you'l be ok. After filling it full of fluid, take it for a spin or allow the rear wheels to spin and
re-check the fliud level.

 

[corvette66]

Bam!!!

Got mt doors off!! wasn't too bad. thanx

Well funny thing... the first time I noticed my OD not working, I changed the fluid, and it was a little dark. I never changed it since I had it till then. So it may have been just because it was such old fluid. Then after changing the fluid, (wich didn't help) I drove the car for about 2 weeks before I drained it, and removed the OD. The fluid wasn't even dirty the 2nd time. So i don't know.

Side note: The OD clutches are more worn than the direct driven clutches. The driven clutches are more "waffled" and have more friction surface. The OD clutches are not "waffled" they just have diagonal grooves. and the grooves are not real deep. So the OD clutches are thinner looking than the driven clutches, but none of them LOOK worn.

I e-mailed 5SPEEDS.com but they gave me a 3 word explanation something like... "could be a clutch" thanx BOB So-and-So
oh well

if anyones look'n for me, tell'em i went fishing.........for a trani tech

dan

 

[corvette66]

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jonM hey how did you creat that web page for your car? I 'd really like to do that. Is it one of those free web builders or dose it have a monthly charge?