I'm planning on changing my Rear Differential to a 3.73. I have an 86 with a manual transmission, so I believe that makes is a Dana 44 assemby (3.07 ratio). I've found the gears and the speedo for about $335 total and the whole assemby for about $1000. I was just wondering how difficult a job it would be to just change out the ring and pinion myself instead of the whole assembly. If anyone has done this or knows of any postings on here, please let me know.
Thanks!

 

You may want to reconsider this. The past has shown no gains with an L98 and shorter gears.

 

I suggest reading the tech tips in the following link: http://www.ring-pinion.com/tech.shtml

Tom Piper

 

Scorp is right on, with the L-98 the engine does not rev high enough to make use of the steeper gear, it is a low end torque motor so you want to keep it in the torque curve.

 

to answer your question, If you have never set up a rear before, dont do it without knowledgable help.

Its not that its hard, but everything must be done correctly! Even if you have a shop install the ring and pinion, its still way cheaper than bying a new unit.

As for the other comments/suggestions about gear ratio, I agree with previous posts that suggest that you rethink your setup. I wouldnt go lower than a 3.07 for a stock L-98

just my $.02

 

I know I said it backwards earlier, so i'm just eliminating this line so that people that don't read the whole posting don't keep repeating things


[Modified by 86_RedRider, 4:33 PM 2/11/2003]


[Modified by 86_RedRider, 10:31 PM 2/11/2003]

 

for an L98, don't do it

 

'86_RedRider,

I've been running the 3:75 (Drive Train Specialities) gear for the past 10 years in my '86 L98. Their number...1-800-521-0628,... they are located in Warren, Michigan. Good people to talk to.

I bought their 3:75 Gears, and their Installation Kit for $434, November, 1993.

When I got these gears installed 10 years ago, I quickly realized, I had much too much gear for my stock '86 engine.

However, my '86 engine is now modified to the expectations I've planned over the years, and the 3:75 gears work for my engine mods really well.

Based on me having been, exactly where you are right this minute, and according to what I see in your signature, and by what I read in your post, I would not recommend the 3:73 gears for your Vette.

The reason for this, is basically a repeat of what Scorp, and Phil mentioned.

Unfortunately, the way your L98 engine is presently configured, I'm afraid your engine would quickly run out of breath...going through the gears, and shifting at 5000 RPM's (if that is where you pull your gears). It would be just too much gear for the stock engine to handle.

That being said...if you think you may be doing any modifications to your engine in the future, then "yes" the 3:73 would be a very good gear for the L98. But, you have to get your engine modified to turn at least 6000 RPM's, to make it a worthwhile mod.

10 years ago, when my 3:75 gears were installed by my mechanic, my costs were Parts + $200.

This would be a good way for you to go...since you already have the Dana 44.
After you get some mods done to your L98 engine, then go for the gears.

I don't know how deep your pockets are, but if $$$$ are no problem, you could in fact buy the 'whole assembly' and change it over once your engine mods are complete.

If you buy just the gears for $335, you're still going to need to purchase the Installation Kit...for another $100. Before I bought them used, I think I would
try to buy them new. There are several companies who offer these gears for your Dana 44. Jeff Kopp, may be another very good source.

Here is what I suggest you do prior to installing the gears.

You definitely need to get your engine to breathe, and make some rear wheel horsepower. You're off to a good start with your exhaust system mod.
Plan on a set of heads in the future. The '86 heads have their limitations.
Try to stay within the 9:00/10:00 to 1:00 compression ratio range, due to todays gasoline octane. (You don't want your engine 'pinging' on you).
Pick a camshaft that you would like to run, in the range you want to be. (Example: 5600 to 6200 RPM's).
The present L98 Maniflod is a real good torque manifold, just the way it is. However, what your engine is going to need if you go for the 3:73 Gears...is a much better manifold,... to once again...help the motor breathe.
Yes, you can modify the stock '86 manifold...which I did too...but now that I've added a Mini Ram, I see that those efforts were not worth the man hours.

If you haven't already done so, I suggest 'opening up' your air filter housing as suggested by TPiS, and also removing the screen on your MAF Sensor, to help get more 'cold air' into the engine. These mods are very easy to do yourself, and may take all of two to three hours to complete.

Last, but no least...you now have to think about having a 'new' PROM programmed for you, or your existing one reprogrammed, for the new mods you complete. It does make a difference, and will help keep your 'codes' from tripping.

Just a few things more, for you to think about, before jumping into anything else.
Hope this helps, and good luck to you. :yesnod:

John

PS: I think what you wanted to say in an earlier post above: was that for every 'one' tire revolution...the driveshaft will 'rotate' 3.73 times.


[Modified by UDLUV12, 1:11 PM 2/11/2003]


[Modified by UDLUV12, 1:22 PM 2/11/2003]

 

One of the reason the gears work so well for you is that you have a MR intake. SuperRam don't seem to like much gear more than 3.07 gear either.

 

Do not go to a lower gear than 3.07 with an L98, youll be out of your power band too quickly, unless you plan on adding a Miniram intake.

 

3:73 worked fine for me??? i run the bottle and blower and i do fine withe 3:73's and not only that but you get the jump hard on alot of other cars! and they are playing catch up! i recommend them! :thumbs:

 

UDLUV12,

So if I open the intake a little to get more air in (and the exhaust is already free-flowing), the 3.73 diff should work. I'm planning on adding a forced air induction (similar to the one they sell that goes through the license plate in the front), do you think this is enough? The open-air lid is taken care of, but I'm worried about the MAF screens. Have you ever had a problem with debris hitting the relays inside? I also noticed that you have the Air Pump Eliminator, is this the one that uses the same stock belt? I heard you could have problems if you change to a smaller belt size.

Thanks for your advice.

P.S. how do you get the picture to show up in the signature?
:withstupid:

 

While on the subject are you saying that a 2.59 setup is better than a 3.07 on a L98 since you'll stay in your powerband longer?

 

I have the 3:45's in my '86 withthe ZF 6-speed. I had the 3:73's and they were waaay too steep. If you really like rowing the gears around town, go for it. I get tired of shifting with the 3:45's and often times will start out in 2nd and shift to 5th when cruising around town. The 3:45's seem to have pretty good performance, but I would have probably gone with the 3:07's if I could do it over again.

 

[QUOTE]Wouldn't this be a direct effect on how the rear wheels spin. For every turn on the driveshaft, the rear wheels turn 3.73 times instead of 3.07?


You have this backwards, Example is for every 3.73 turns of the DRIVESHAFT the WHEEL turns 1 time.

 

'86_RedRider,

Yes, you can open your stock '86 Intake Manifold, and you are sure to pick up a few hundred more RPM's. I do not recommend this, as I now know...it wasn't worth the man hours. However, I believe it all depends on how far you plan to go with your mods?

If you have no plans to get another set of heads, then I say yes, open up your stock '86 manifold, and then you may want to look into some porting and polishing on your stock heads. Perhaps even a valve job (you made no mention of the mileage on your Vette).

I tried this, and the best I got, was another 500 RPM's...after several (at least 6 times) manifold off...manifold on. After doing this mod, hell, I thought this was the ticket for me...only to fully understand the tremendous impact the Mini Ram install would be for me, a year or so later.

You see, I had the Heads, the Headers, the ZZ9 cam and lifters, the MSD Ignition Box, with the 3:75 gears, and of course the stock '86 manifold that was modified (opened-up). Not many from my town could stay with me...so naturally I thought...hell...why change anything...it's running good.

The more I ran the car the more I understood that there was 'more HORSEPOWER there to be had.' I could actually feel it in the pedal. The only thing that kept glarring at me, was the fact that I was still running the stock '86 manifold, even though it was modified.

So, just this past summer, I bought the Mini Ram II...installed it a few weeks later, and I'm telling you, I can not believe the difference this manifold has made for my configuration.

Talk about 'Breathing'...my shift points are 6200 RPM's, and this motor has never 'pulled' so hard on the top end.

I've had the engine to 6700 RPM's for a one time 'look, see, and feel'...but because the ZZ9 cam only makes horsepower to 6250 RPM's (per TPiS)...there is no need for me to push it, and I don't.

Sounds like you got the exhaust system where you want it, and what you've done, reads good.

Here are my thoughts on the 'Forced Air Induction' system you are planning to install.

I'm still running my stock '86 Vette Air Induction System!!!!!
Yes, I've opened the lid, and I use the K&N Filter (reuseable), in addition to removing the screens from the MAF. (No longer a daily driver...as I only enjoy running this Vette on clear, dry days).

I'm convinced, for my particular application, my Vette runs just as good with my stock Air Induction System...as those of my friends who have purchased other Systems from both TPiS, and I believe, Summit.

There are two trains of thought here. First of all, I like the stock design, and I feel...what is the point of installing an Induction System...when there is only so much 'air' that my throttle body can handle.

The way it's running right now, I just don't feel the change would do me any good. It may very well work against me...as I 'picture' too much air being forced into the plenum, and the engine 'falling', and 'bogging' all over itself.
Sometimes, too much is not a good thing.

Now, I'm not telling you not to go out and buy yourself a good Air Induction System. There are a bunch of forum members, whom I've read about in the past, that talk of their gains from this very install, ...and I believe them.

At this point...I just don't think it would be a worthwhile install for me.

As far as the Air Pump Eliminator Kit, yes, this is the one where you can use your stock Serpentine Belt. At the time of install, I thought it would be a good idea for me to install a new belt, even though I only had about 18K on the old one. I keep it for a spare...just in case I throw or break one.

Yes, I too have heard about some guys going to a shorter in length belt, after doing this mod, and having problems with their belts. I'm sticking with the stock belt.

Good talkin' to you RedRider!!

John

 

I have 3.07's in my '87 w/ ZF, and I can tell you that you do NOT want to have 3.07's with the ZF trans. The gears are taller all the way through the ZF, and 6th gear is absolutely useless below 75, even as a cruising gear (I get worse gas mileage in 6th at 70 than I do in 5th). Right now I'm debating between a set of 3.73's for mine and 3.45's. I can get both for free (both owners owe me for work :D ) However, given the state of my car right now and the mods to be coming soon, I will likely be going with the 3.73's.

 

Well, that does makes me feel better about the 3:45's. There are a few "in between" ratios available such as the 3:31. I think that when considering gears, the most important consideration is how you will spend most of your time using the car. If you spend most of your time at the track, steep gears are good as long as they put the motor in its optimum RPM range. But if you spend a lot of time commuting or just cruising around, steep gears can get tiresome. Not only were my 3:73's a PITA because of all the shifting and skipping gears, I noticed a real driveability problem at low speeds. I don't know how to describe it other than it was a lot more work to keep the car moving smoothly and preventing it from chugging and lurching its way along below 25 MPH.

 

I installed 3.73 in my 86 automatic and it was a night and day difference.I had 3.07's and love the gear change.I did know that I would need a better intake system to take advantage of the gears.But since then,using the stock TPI,its been fine with me.Im sure at the 1/4 mile track,it may be a bit too much but on the street and driving anywhere,youll go too fast for legal speeds before youll ever feel your engine running out of the powerband.
At least in my case,thats how it is.

My car pulls hard straight up to 90 mph and I dont choose to go any faster on the roads.Take off speed,mid range passing power is greatly improved.The fun factor is where its at as well.I think too many people read about it but never drove a 3.73 TPI car enough to see the difference and pros and cons.If youre building a 1/4 track car,then stay with 3.07's.

In the real world and on the street and highway youll be going 100+Mph before your engine will feel rpm starved.In fact,with 3.73's the car stays and goes in its powerband between 2,000-4800 rpms faster and easier.
I also have a different cam in the car that makes it power from 2000-5500 so I think that helped somewhat.The stock cam may not be as good with steeper gears hence may be why some guys here that have drove the cars with the gears have noticed it running out of steam somewhat faster.

Down side is MPG is down a bit and highway crusing rpm is increased a bit.Wheelspin may be a problem as well since its really easy to spin the tires and more so on somewhat slippery roads.ie:sand,gravel,wet,etc.
I do hope to install a mini ram or stealth ram someday and a 2800 stall to compliment the gears and go have some fun at the track then.Until then,my 0-65 mph blasts is too much fun to even complain about having too much gear.

Before I forget,I didnt install the actual gears but bought the whole rear end with the gears in it and did a swap.Pretty easy job to do as well.
:)