Bucs34

Hi everyone, I need some opinions on what to do. Currently I have a 85Z51, 90K with a 4+3 tranny. The problem with it is that 2nd gear randomly grinds . Its only second gear and it doesnt matter if Im on it or taking it easy, its completely random. So heres my question:

I have $1000 to spend, should I look into getting the 4+3 fixed? Or should I swap out for a different tranny? If so what are my options? Im leaning towards going new tranny because I dont really like the OD and I hear theses trannys are problematic to begin with (learned that after I bought the car).

Thanks for the help in advance!

Kubs

I would try and swap it out for a ZF6 if you can find everything you need in your budget. I think all you need is a new slave cylinder, clutch, and used trans.

RacerX70CC

Drive it and save your money for a swap to a 5-speed (Kiesler conversion), or 6-speed (Richmond ROD). Neither option is cheap.

I personally wouldn't do a ZF swap as they're getting hard to come by, plus there's the brain damage of the flywheels and hydraulics to contend with. However, some on here will disagree, so take any advice you get on a forum for what it's worth... free.

You could have the 4 speed part repaired of your 4+3 (it is nothing more than a Borg Warner 4-speed forward of the OD unit), and from the sounds of your description, it has either bad synchos and/or a worn out shift fork. Saying that, I must at this time inform you that my crystal ball is still not back from the shop, (parts for it have been on backorder for the last 15 years now), so do not take this as a dead-on diagnosis. Repairing the 4+3 can become a pig-in-a-poke, so prepare yourself if you decide to have it repaired.


Best of luck to you!

1985 Corvette

Maybe use the $1000 to repair the 4+3? I'll be in the minority for that but if you invest money into a quality rebuild, I would think that would be better than starting at square one again so to speak.

For $1000 you'll pick up a used Z/F with plenty of miles on it that one point or another will start giving you issues all over again. I'm talking with a guy here in Florida that rebuilt his own overdrive off his 4+3 for around $400, including purchase of the tools needed. Not bad compared to the $1200+ service some specialty shops charge for an O/D rebuild.

I don't hate the 4+3, quite the opposite I find it unique in its operation. Yeah, it's an oddball but I just can't help but like it.

pologreen1

5-speed Kiesler conversion I know they had a big sale not long ago, I am sure they can help you in this economy they probably are not flying off the shelf.

6-speed conversion, one or 2 sets of pieces for the swap in F/S right now.

c4cruiser

Have you checked with a reputable repair shop to see what repair costs would be? If you only see occasional grinding going into 2nd, I would also suspect worn synchros or a worn 2nd gear shift forks. A small parts kit (includes the synchros) for the 4-speed portion is not a lot of money. The trick is finding somebody with the experience to separate the OD from the 4-speed and get them back together.

Upgrading to a ZF6 is a little more involved than just getting a ZF6 and bolting it in. It's a good trans, but unless you know you are getting one in good condition, the cost of rebuilding a ZF can be a bunch.

The Keisler is a good tranny and it is a straight bolt-in swap. The gear ratios are similar in 1st thru 4th with only a slight differnce in 5th compared to the 4+3 4th/OD ratio. But expect to pay somewhere around 2 large for one.

Richmond Gear has a 5-speed and a 6-speed that is a bolt in but they can also be pricey.

rodj

Once again, all the guys saying swap it out don't actually own one

88BlackZ-51

fyi. i will be selling my 4+3 in a few months. it's from my 88 (best year for 4+3).

anyways, i will be letting it go for around $600.

car has 75000 miles on it, and it shifts flawless.

powerpigz-51

Any kind of swap or conversion is going to probably cost you close to 3 times your budget. A rebuild of the T10 would be much, much cheaper and separating the OD from the 4 speed is not that hard. Since the 85 OD is one of the early, more problematic units, I suggest you find someone selling the 4 speed and OD unit out of a later year. (86 on up) You can find one of these for less than a grand. If your current OD still works properly, I would go for the rebuild of the 4 speed and maintenance the current OD, (fluid and filter change every 10k), shifting it only with the clutch and using it only when needed.

skybolt31

Another inexpensive option is to swap it for a T-5. These will not handle the power of the other swap's mentioned, but if your car is stock and you want to fix the tranny problem without sinking a lot of money into a car that isn't worth that much in the first place, this is something to consider.

http://members.cisdi.com/~anesthes/f-car-t5/

88BlackZ-51

2 much work to do the T-5, and its from a 305.

Bucs34

Thanks everyone for the ideas so far. Has anyone ever had thier 4+3 rebuilt at a shop? how much did it cost?

RacerX70CC

I do (or did)... but I swapped to a TH400 (better for drag racing), thus making the manual trans dilemma moot.

Had I decided to stay with a manual, I would have swapped it out for a 5 or 6 speed. The clumsy factory shifter (even with the "short throw" links I put on it), with no aftermarket support is a big reason, plus the problematic OD unit (mine is good, having been recently rebuilt before I bought my '85), made it a no-brainer, at least for me.

Bucs34

How about this option...swapping it for an 88...Any benifits? Will it be a direct bolt on?

powerpigz-51

I have a 88 in my 85, direct bolt in. The 88 does not have the cable to the throttle body, this does not affect operation in any way. The OD will still kick down to passing gear. That is a great deal, I would jump on it if I were you. Then you could sell your good OD and make most of your money back.

rodj

You will need to change the O/d switch in console or use the '88 shifter with button in ****.
'88 has momentary switch whereas early models had a OFF/ON switch
$5 from Radio shack

powerpigz-51

I am using the original console switch.......

helphos

Have you taken a close look at the slave cylinder or the Master cylinder? A slight leak in either could cause 2nd gear to grind, while the others seem unaffected. Rebuild or replace the hydraulics and you could solve your problems. No guarantees, but it worked for me with a ZF that 'lost' second gear.
Good Luck!

powerpigz-51

Helphos is right, worn components could cause the symptoms you describe, including a worn clutch assembly. The clutch should be engaging a good ways up off the floor. Other symptoms would be difficulty putting it (grinding) in reverse.

Bucs34

Thanks everyone for all the input. Is it worth it to bring it to a shop and have them tell me what it will cost to be fixed? Or, is it going to cost a good enough amount for them to even look where itll be to the point that I should just get it rebuilt?