Ryhnoz60vette

I swaped a 1990 ZF6 speed into my 1986 coupe that had the DN 4+3 trans, so my car has a Dana 44 with a 3:07 gear ration from the factory. My question is what gear ratio do I need or what's the best to get to go with my ZF 6 speed. My car is not a race car just a street cruiser. Theirs a guy on the forum selling some gears from his 1996 corvette, I think they are 3:43's , would they bolt right into my car? Thanks for your help.

Ryhnoz60vette

Sorry the gears he is selling are 3:45's? From a 96

FASTAZU

3.45 will work fine but 3.73 would be nice with your stock HP range.

Benny42

I did a T56 swap (same ratios) and the 3.07 drives pretty good. I completely agree
with We Gone, either 3.45 or 3.73 would be perfect.

Ryhnoz60vette

Ok, great thanks for the info. I guess all I have to do now is track down some 3:73 gears. Lol thanks again

pkincy

Given that you already have a line on a set of 3.45s and just do street duty, why not take the ones you can get?

WVZR-1

I'd have to agree here with taking a 3.45 that's already set up and a bolt in or close to a bolt in. The sale of your 3.07 could get you very close maybe to even for the parts swap. You would only have maybe the labor of the exchange or DIY. If you could land a 3.33 from an '89 or '90 that might do well also or even a 3.54 if you found one of those. 3.73 might be steep.

If you get a D44 from a later C4 you'll only need to either get the camber brackets from the later one and drill the rear cover to match the larger bolts required or just drill your camber brackets as well as the rear cover when you do it.

The price and the condition of the 3.45 that's available I believe would make or break the value of the swap.

mtwoolford

even with 345's in my 96 six speed, sixth gear is pretty unusable except at higher freeway speeds; remember the sixth gear is an ungodly 0.50 overdrive; at 2000 rpm I'm doing roughly 84 mph; with 307's you'd be doing what? 100 mph?

MJFuss

My '89 M6 has the stock 3.33 gears. 6th gear is very usable on the highway. In fact, I often leave it in 6th going through towns where the speed limit is 45.

Don't underestimate how well these TPI motors can pull right off idle. Mine will pull the car up a slight incline with my foot off the gas pedal... in 3rd gear. Try it.

You might be giving up some performance with your 3.07 gears, but the drivability should be just fine and you'll probably get tremendous fuel mileage.

hcbph

Have you tried running with the current 3.07's? I've got a Tremec TR3550 5 speed behind mine and with the 3.07 it handles cruising at 1800 rpms at 75 mph and has gotten 32 mpg out of it. It does OK around town and still does very well on the highway. About the only thing I've noted on mine is first gear seems a little steep for my taste but it's livable.

WVZR-1

Yes, I'll bet the 3.27 1st (I think) would be a handful.

That's precisely why I mentioned the 3.33 axle ratio in my comment. I believe you need to completely discard all thoughts regarding 6th gear in the ZF. Nearly all ZF failures are 6th gear related when higher speeds and lack of lubrication create "heat" related failure and "lock-up". 1 - 5 in the ZF is tough, 6th is certainly questionable.

If the 4+ was comfortable in the OP's car, the ZF should be great in the same car with the 3.07. The ratio matches are very similar, a 3.33 if one was available with a near stock engine might be great but if a 3.45 were available for less $$$, that by itself might justify the 3.45.

Forget about entering the 6th gear ratio into the mix.

It's good you commented. That's why I mentioned the 3.33 in my original post and mentioned I thought the 3.73 maybe steep.

Ryhnoz60vette

Wow, thanks for all the info. Definataly gives me something to think about. So should I even change my gear ration then? Is it even worth the time/money . I've never really driven my car since the 6 speed swap, besides a few test runs in my neibor hood, my car isn't road worthy yet, and I'm in the process of doing all the body work and getting it ready for paint. The gears that I mentioned that were available , he's asking 100$ is that a good price? He says they have about 90K mikes on them from his 96 vette. Also, since the heat issue was brought up, what's the best trans oil to run in the ZF's?

WVZR-1

It sounds like he's selling only "used" gears. I'd maybe avoid that buy unless you're very familiar with ring and pinion installs. You would need an install package that's likely $160 or so $$'s and then the labor to remove and rebuild yours with nothing to resell. I thought you hinted that the sale was for a 3d member which would mean you could resell your 3d member.

If you've not driven yours WAIT and I doubt you'll be as interested in the change. If you are I'd try for a 3d member exchange because your 3.07 is very resalable especially if quiet.

Ryhnoz60vette

Ok, thanks ALOT WVZR-1 for all your help. I greatly appreciate it. What's the BEST oil to use in my ZF?

WVZR-1

That gets debated frequently. I have plenty of the GM/OE that's not available any longer and I've used the Castrol 10W60 that ZF recommends with no issues. Some use AMSOIL MTF and like that. There's several choices and I'll avoid that conversation. I don't like the AMSOIL "SHOVE" to promote their product.

A search will find hundreds of conversations.

I believe that frequency of service is maybe more important than the product of choice but I'd stick to a motor oil based product for myself. Be sure and remove the side fill plug before removing the drain plug for service.

Ryhnoz60vette

Ok thanks

Lloyd Smale

ive got a 6speed 92 and the 345s seem a bit to high geared for me. Keep in mind that im more used to older muscle cars though. If i was going to do it id put a set of 410s in it. You have plenty of overdrive built into that tranny to still get good gas milage. I surely wouldnt go any higher then a 373. Keep in mind that even these corvettes were geared as a compromise to meet epa gas milage standards.

vl5150

I have a 1990 L98 with the ZF6 and 3:33 gears. The car was stock when I got it. Here's my impressions:

With the stock HP output, gears 1-5 are fine. 6th is not effective as a pulling gear and is quite sluggish with stock power levels when trying to accelerate at highway speeds. It's a "cruise control" gear for fuel economy and will hold speed on the highway. Down-shifting is required for regular passing. So I would recommend the 3:45 gears if left stock. However I was displaying 30-32 MPG stock in 6th at around 70 MPH with the 3:33/1 ratio.

Just doing the headers, Y pipe, and 1.6rr's gave me enough power to pull in 6th gear with out down-shifting and later when I did the full long tube runners and intake helped a little more. So for me the 3:33's and .50 OD are working very well now with the car's power levels and can pull 6th at an acceptable rate now. I display around 27-28 MPG now at 70. Difference when making a pass in 6th at 70 MPH is very slowly passing a car stock vs blowing by a car.

Keep in mind that L98 and LT1 have different gearing requirements with the L98 needing a lower numerically gear compared to the 92 and up LT1's. I think a 3.73 would be annoying in an L98 and 4:10 would be unlivable and perhaps dangerous in the wet given the 1st gear ratio.

The 6th gear lack of pull was the main reason I decided to modify my car. Just my $.02.

Ryhnoz60vette

Well thanks for your 2 cents V15150 LOL. I appreciate your info .

pkincy

I have had 4.10s in a ZF 6 speed. Although you certainly can use 1st, you also can start in 2nd except uphill. You also get to use 6th a whole lot more. My idea was to spend more time in 3rd and 4th rather than 2nd and 3rd and it does that.

That was in my 94 Z07. I frankly do not remember what I have in the 93 I have now. I think it is the 3.73s from my 94 Z07. I traded the entire batwing out with my buddy who built the 93 Fortieth. He had 4.10s and had serial number 1 vortec for the LT1 put on the 93 and it was too much gear for all that power. I had 3.73s in my Z07 and a stock motor and wanted the 4.10s. We traded and then I sold the 94 and bought the 93 from him. Too many cars, too many aftermarket parts and too much age to remember all that clearly. <g>

Given the 6 speeds you can use anything from the 3.07s to 4.10s without a problem.