4+3 trans related

[grumpyvette]

corvette 4-3-transmission fluid replacement procedure - Google Search

1987 Corvette 43 Overdrive Specs
The fourth-generation Corvette, referred to amongst enthusiasts as the C4, debuted as a 1984 model. From 1984 through 1988 the manual transmission on the C4 Corvette was a Doug Nash 4+3 Overdrive unit. This featured a unique setup in that it was a four-speed manual, but the second through fourth gears featured a push-button overdrive feature for added fuel efficiency. Despite its reliable gearbox, the car's overdrive function was prone to failure.

The C4 Corvette had a General Motors' L98 engine. This V-8 engine has 5.7 liters of displacement. It is a cast-iron block with aluminum cylinder heads. The L98 is an overhead valve engine with a four-inch bore, three-inch stroke and a compression ratio of 9.5-to-1. This motor uses tuned port induction to deliver fuel to the engine block and produces 240 hp at 4,000 rpm and 345 foot-pounds of torque at 3,200 rpm.
Doug Nash 4+3 Overdrive Transmission

In addition to the four-speed automatic transmission, Chevrolet offered a four-speed manual gearbox in the 1987 Corvette. This floor-mounted stick shift was on the center console and featured an overdrive option that would engage on the top three gears for fuel efficiency. The first gear has a 2.88 ratio, while second through fourth had 1.91, 1.33 and 1.00 ratios, respectively. The overdrive gear featured a .67-to-1 ratio, while reverse was 2.78-to-1. The final drive ratio of this gearbox was 3.07-to-1.
Dimensions

The 1987 Chevrolet Corvette sits on a 96.2-inch wheelbase with a front track of 59.6 inches and a rear track of 60.4 inches. The body of this two-door sports car has an overall length of 176.5 inches, width of 71 inches and height of 46.4 inches. This sports car has 16-by-8.5-inch rims with either P245/50VR16 tires or the slightly wider P255/50VR16 tires

Originally Posted by c4cruiser
Changing the ATF fluid in the OD unit is not hard at all and it's just like you have found out. It would help to get the car as high as possible so you can access the pan bolts. There's not a lot of fluid in the pan (roughly 2 quarts) so a small drain pan is all you need to catch the old fluid.

Start by removing the fill plug! If you can't do that, there will be no easy way to refill the OD. Remove the bolts but leave two corner bolts loose. Once you start to pull the pan off the housing, the fluid will start to drain out. Once that finishes, pull the last of the bolts to remove the pan. Pull the filter straight down; it's held in place by a rubber grommet. Save the grommet!

Clean all of the gasket material from both the pan rail and the rail on the OD housing. Clean the pan using a solvent or even brake parts cleaner. Remove the magnet and clean it too. Replace in the same spot in the pan. Make sure the pan rails are straight and the edges around the bolt holes are level with the rail.

Here's some part numbers for a new filter. The filter is the same one used in some Ford FMX transmissions found in early 70's Mustangs, Torino's and even a few F-150's:
Carquest 85926 (now Advanced Auto Parts and the p/n may be different
AC Delco TF 184
Fram FT 1024
NAPA ATP14717
Ford D0AZ-7A098-A

These should run about $8 to $10. The do not come with a grommet so save the old one.

Use a good black RTV sealant on the pan rails making sure you go around the bolt holes. The bolts don't need to be very tight but they should be tightened equally.

Use non-synthetic ATF such as Dexron III. You should be able to find that at any parts store. You will need a pump to get the fluid in. Use one that screws onto the bottle and will allow for attaching a short piece of tubing.
http://content.mamotorworks.com/pdf/603817.pdf

http://www.mamotorworks.com/corvett...uild-kits+1984+1988+4+3-manual-1-327-735.html

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

http://www.ecklerscorvette.com/corvette-transmission-rebuild-kit-doug-nash-4-3-1985late-1988.html

http://www.5speeds.com/dne.htm

http://www.5speeds.com/43table.htm

http://www.ecklerscorvette.com/corv...rive-rebuild-kit-doug-nash-4-3-1984-1988.html

http://forums.corvetteforum.com/c4-gene ... pdate.html

http://www.ecklerscorvette.com/corvette ... -1988.html

http://tech.corvettecentral.com/2007/01 ... nsmission/

http://www.ecklerscorvette.com/corvette ... uct_Viewed

http://forums.corvetteforum.com/c4-tech ... ide-2.html

http://www.vetteweb.com/tech/vemp_0511_ ... ewall.html

http://www.mamotorworks.com/corvette-c4 ... 7-735.html

4+3 filter LISTED ON A DIFFERENT SITE


Carquest # 85926
AC-Delco #: TF184 ($4.50 at Rockauto.com)
Fram #: FT1024 ($9 at Kragen)
Napa #: ATP14717 ($8.50)
Ford #: D0AZ-7A098-A
General Motors #: 12339143

 

[Stick the Corners]

My next project is to replace the fluids on my 4+3 transmission.
Studying the service manual and some links, it seems the only gasket and filter is on the overdrive unit. While I do not see any o rings or plug gaskets for either the manual or overdrive side, there is mention of an o ring that goes somewhere when replacing the overdrive filter. Does anyone know anything more about this, or it’s replacement since the filter and gasket kit from Napa does not indicate it comes with it?

There was some conversation on the link to use the existing one; on my car, this o ring could have been replaced on my overdrive rebuild x2 by Chevrolet under warranty around 1986 or 87, and again around 1990. That means it would be 33 years old with probably 20,000 miles since that overhaul. It might be friable from age.

Also, what is the preferred material to use to seal the overdrive gasket?
Does that sealer go on both surfaces of the gasket? Probably need to be careful not to have any excess oozing into the OD fluid.

Update:
I was able to order a kit from Corvette Central that had the O ring(grommet), gasket, filter.
The other links in the thread mostly got me down a rabbit hole with Napa, even after cross referencing some of the part numbers listed from Ford, GM, Fram, A/C Delco, and Napa itself.

Also, I reread the post above where “c4cruiser” talks about using RTV and grommet. But besides making sure the sealer is around the holes, it is obvious that RTV goes on both sides of the gasket?

 

[Stick the Corners]

When replacing the transmission fluids, and the differential fluid for that matter, the service manual calls for the 4speed (manual side) using 2pints Sae 80W or 80W-90 GL5 gear lube, and the overdrive 4pints of Dextron II automatic transmission fluid. Several enthusiasts I spoke to are recommending Amsoil products.
Paul Cangialosi, someone who repaired these units for GM for many years, emailed me his recommendation of using Royal Purple Synchromax in the OD and Royal Purple 75-90 or 85 max gear lube in the 4 speed.
Since I am in the Northeast with freezing winter temps, does anyone else have specific recommendations for both sides of the transmission, and the differential?

I did reread c4cruisers comments about the fluids, where he recommends non-synthetic ATF Dextron III, but I believe that was written a while ago, and hopefully lubricants and fluids are better now.

 

[Stick the Corners]

Still looking for guidance regarding the need for using sealer on both sides of the overdrive pan gasket.

Besides that, what would be the favored sealer? Here are two that look good; which is best for this application or should I use something else? C4cruiser suggested Black RTV, but the person in the 4+3 video used the high tack.

1)Permatex 80065 High Tack Spray-A-Gasket Sealant, 8 oz. net Aerosol Can
or
2)Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker

 

[Grumpy]

sealants and threads

OLD POST's COVERS THAT INFO https://garage.grumpysperformance.com/index.php?threads/head-gasket-roughness-ra.15927/#post-95851 http://garage.grumpysperformance.com/index.php?threads/sbc-head-gasket-choice.11070/#post-79067...

garage.grumpysperformance.com

oil pan gaskets

now Im sure most of you guys have seen or used both types, (the old cork 4 piece sets and the newer synthetic one piece design oil pan gaskets) in my opinion the newer synthetic one piece style is FAR superior! if you read the instructions they say to not use a sealant, Ive found that use of...

garage.grumpysperformance.com

which sealant goes where?

OLD POST COVERS THAT INFO I can,t believe the stuff I see at times..in the car mags that are SUPPOSED to be articles composed by guys who know what they are doing!!!!!!! I picked up a copy of one of the more common, Chevy based magazines and theres PICTURES of a guy dipping head bolts in...

garage.grumpysperformance.com

 

[Stick the Corners]

Thanks for those old links; they will come in handy for future projects also.

So if my reading comprehension is OK, it would seem that the Permatex Ultra black RTV , or equivalent, is good for the OD gasket placed on the upper surface, and following the application instructions on the label, ie waiting for setting. For the threads on the pan bolts, it appears that the Permatex High Tack, or equivalent, will be good for that in accordance with the labeled instructions.

There is a diagram in the service manual that shows how the RTV is placed on the pan and around the bolt holes, but it seems no gasket was used in those days.

Will the 6-8 lb ft of torque spec on the pan bolts , or the technique of torque application, be altered because of the thread seal in some way?

 

[Stick the Corners]

It appears from the shop manual for my 84 C4, that the same 4+3 gear oil for the manual side is the same used in the differential ie. SAE 80W-90 GL-5. I will in all likelihood be using the Royal Purple 75W-90 Max Gear lube. But the shop manual also has an interesting note for “Limited-Slip Differential Rear Axle”as follows:

“GM Part No. 1052271. Before filling, add 4 ounces of GM Part No. 1052358 or equivalent (full size and Corvette B, D and Y body) models only.”

Can someone explain whether I will need to add an additive to my C4’s differential besides the gear oil?

 

[Grumpy]

Limited Slip Axle Lubricant Additive - 4 oz 88900330 | GMPartsDirect.com

88900330 - Limited Slip Axle Lubricant Additive - 4 oz

www.gmpartsdirect.com

and its only $8

it helps reduce the noise and protects the friction discs in the corvettes trans or differential yes its advisable that you use it.
one of the guys that used to post on the site, stated it made a very noticeable improvement on his 1987 vette as it reduced drive train noise considerably

 

[Stick the Corners]

Interesting follow up to this:

I ordered the additive from GMpartsdirect.com. I was not too happy about the $19 shipping fee that was added to the $8 part, but whatever.
So this AM I got this message from them that they are holding the order.

“Hi,
Thank you for your order.
Part number 88900330 is not listed in the current licensed GM parts catalog as an original equipment part for the VIN supplied.
The current licensed General Motors parts catalog does not list a limited slip axle lubricant additive for VIN 1G1AY………………. .

We can process your order as originally placed.
OR
we can cancel your order.

How would you like to proceed?

Please remember we do not have any way of telling if a part from another vehicle will fit yours properly without modification to the part or to your vehicle. Please research parts that did not come on your vehicle to make sure they will fit your vehicle. No one wants to be stuck with parts that don't fit due to bad information.

Sincerely,
Floyd
Your customer service agent for
www.GMPartsDirect.com“

It seems they no longer can link old VINs to the new part numbers that supplanted their old part numbers.
But if I queried their search engine for the old part number, it shows the new part number that was ordered.

I guess, just as well. I called up the local Chevy dealer, and they sell the additive for about $15+tax.

This brings up the larger point that if GM no longer makes parts under the original part numbers for our vintage vehicles, additional research will be needed to get the proper parts if they have upgraded the parts with number change.

 

[Grumpy]

and whats even more insane,
I talked to a local chevy dealer in FLA. and he said ,
some dealerships junk/trash parts for cars over 30 years old as worthless inventory talking up shelf space

 

[Stick the Corners]

I called up Royal Purple to just confirm their products compatibility with my uses, since my OD filter just got delivered from CC. First, their Synchromax should be good as the replacement for the old Dexron II or III ATF for the OD compartment.

Their 75W-90 Max gear is good for the 4 speed side.
But what I found interesting was that the use of this same product in the differential comes with friction modifier’s already. The Rep thought that the addition of the GM additive, that we talked about above, was not necessary, and while it would not hurt the diff, it could make it not function as desired secondary to too much friction modifier.

What do you guys think, to add or not to add the GM friction modifier in addition to the Royal Purple Max gear product?

 

[Grumpy]

Personally, Id try it without and listen to the trans and differential,
you'll hear a marked increase in noise and feel how it functions, if its not operating happy, you'll know it
modern lubes are generally better at function than lubes designed in the 1960-1980s,
and see how the Royal Purple Max gear product? worked, if your not happy only then add the GM additive
but your likely not need it.
I've generally found the modern synthetic lubes ( especially trans fluids) marginally superior
this does not always apply to differential gear oils , but in many cases you'll find synthetic lubes have a higher /wider effective heat range tolerance

best differntial lubes - Google Search

The Best Differential Fluids and How and When to Change Them

Your rear differential is one of the most unappreciated parts in your car or truck.It does what might be the hardest job of all of those components, multiplying torque from your transmission and sending it to two rear tires.The whole time, it is letting those two rear tires spin at different speeds.

www.autoguide.com

Rear Differential Lubricant's Temp Range

I got asked what the ideal rear differential lubricants differential temps should be? Changing the lubricant's and additives in the differential if its of unknown age or it looks overly black may help durability, and perhaps order a magnet to place on the outside surface of the rear...

garage.grumpysperformance.com

 

[DanZ51]

Ah yes, the dreaded DNE 4+3 (or 83MM in GM speak). A Borg Warn Super T-10 trans saddled with DNE electric over drive with dubious build quality and assembly. Under sized main carrier bearing (+ lack of oiling) aside, the poor assembly tolerances was a major issue; OD's were built with excessive lash, zero lash, and even a preload (on a ball bearing - Horrors!). And if I'm not mistaken, Doug Nash Engineering was teetering on going belly-up during the 4+3 production. So chicken/egg: Did poor QC put DNE out of business, or was the business poor and QC suffered?

I enjoyed my 4+3 when I had it. But it was rebuilt twice: Once by the 4+3 Guru in upstate NY (30yr ago, the ONLY person in the country that would touch it), and my attempt (20 yrs later). The second time, the carrier plate was too chewed up to get accurate measurements off it, so it's performance was not good. Hence I converted to a T56.

 

[Stick the Corners]

Mine was rebuilt twice, and I think the third was a switch problem, all under warranty about 30 years ago. I’m hoping they got it right the last time and trying to keep it that way with a change in fluids.

 

[Grumpy]

there's always the option of upgrading the transmission, and there's dozens of choices if you have the time skill and cash required,
(of course the options and cash required vary wildly) 4-5-6 speed manual transmissions , and 3-8 speed automatics
keep in mind the c4 vette trans uses a support beam between the trans and differential

1984-1996 CORVETTE C4 AUTOMATIC SUPPORT BEAM LADDER BAR GREAT CONDITION

1984-1996 CORVETTE C4 AUTOMATIC SUPPORT BEAM LADDER BAR GREAT CONDITION.

www.carrollcorvette.net

a bit of fabrication and custom parts work allows use of several options

Chevrolet GMC 6L90 Remanufactured 6-Speed Automatic Transmission - Powertrain Products

Find high-quality Chevrolet GMC 6L90 Remanufactured 6-Speed Automatic Transmission at Powertrain Products, home of the Pure Care Warranty!

shop.powertrainproducts.net

Id talk to the vette2vette guys if you need parts

Vette2Vette

We have over 125 car parts from 1984-2004 in our 25,000 square foot indoor facility, with additional corvettes and parts arriving all the time. We offer new, used, rebuilt and reproduction parts.

www.vette2vette.com

 

[DanZ51]

T56 with "C" beam adapter.

 

[DanZ51]

This is the adapter I used for Chevy T56. It was built by (now defunct) Pro Street Customs. The other (3) pictures show an T56/C4 adapter someone fabricated (unknown). I've heard Three Pedals offers an adapter, I know nothing about it.

 

[grumpyvette]

thank you for the info and pictures , Im sure it may help some members
and at the very least get then thinking about custom fabricated adapters
and how having or owning a drill press and a decent welder or ideally a milling machine or at least a friendly local machinist might be helpful,
if nothing else

a dial caliper. a pad of paper, a magic marker, some fabrication skills ,
and owning a drill press and a decent welder or ideally a milling machine
can allow you to do amazing things in the correct hands,
especially when getting what you need is not available off the shelf

 

[DanZ51]

thank you for the info and pictures , Im sure it may help some members
and at the very least get then thinking about custom fabricated adapters
and how having or owning a drill press and a decent welder or ideally a milling machine or at least a friendly local machinist might be helpful,
if nothing else

a dial caliper. a pad of paper, a magic marker, some fabrication skills ,
and owning a drill press and a decent welder or ideally a milling machine
can allow you to do amazing things in the correct hands,
especially when getting what you need is not available off the shelf

Yup. The Pro Street unit wasn't overly complicated to fab. But their price was quite fair, and purchasing (as opposed to fabricating) made the swap much quicker.

 

[Stick the Corners]

Finally got all corners on jack stands and ready to change the fluids but nothing is easy for me. I’ve had penetrating oil on the transmission filler and drain plugs. I’ve been initially directing attention to the fill plug, since if I can’t open that, no point in attacking the drain on the 4 speed part of the transmission. Of course, that fill plug was partially mangled at some point on those rebuilds that were done years ago. It looks like a multifaceted socket was used to mangle one corner of that square plug. I’m not completely sure about what tool is the best in this situation but I had a heavy gauge adjustable that I cinched up pretty tightly as I was worried about rounding. I whacked it with a wooden mallet some but not sure I got anywhere. The plug doesn’t appear any worse so after more penetrating oil, I’ll try again tomorrow.

There does seem to be some difference in what tool fits the other plugs. One YouTuber specifies a 9/16, but I found a 14mm was tighter. Mine are open ended wrenches but I think a closed type wrench is something I need to purchase.
Any advice on this or how to manage the mangled plug is appreciated.