I am in the process of rebuilding my 1987 Corvette "YDM Code" 700R4 Transmission. The late style with the auxillary valvebody.

I need to replace the original Reverse Input Drum assembly. I am running a Wide style Carbon 2-4 shift band.

The original replacement 1987-1992 Reverse input drum has been discontinued by GM, #8681295.

I have only found sources that stock used - recondition units for the 1987-1992 700R4 trans. Turned in a lathe and then polished.

GM has a superceeded #24241494 Reverse input drum that they list for all the late 1987 to 1993 700R4 transmissions.

Upon checking this part number with my local GM parts counter person, #24241494 Reverse Input drum is used to present in all the GM 4L65E transmissions to 2010. And is also used in the 1 year only 2005 C6 Corvette 4L65E transmissions.

My ATSG Techtran manual says that there are 3 specific types of 700R4 Reverse input drums that were produced from the 1982 to 1993 700R4 transmission production timeline.

The 1982 to Early 1987 style.

The Late 1987 to 1992 style with a Bellville Plate in the Clutch Pack. Ball Capsule eliminated in the housing. Uses the cast aluminum piston. Requires Pump Cover with .215" Hole between the sealing rings. Has Round .095" Orifice Hole between the sealing rings in the housing.

The 1993 Model Only Style that has identical Specs listed as the Late 1987-1992 Reverse Input Drum But instead used a Large square Hole Between the Sealing Rings in the Housing.

The ATSG book specifically states these different styles of Reverse Input drums will not interchange.

What GM is selling now is a 1993 on up Reverse Input Drum with the Large Square Hole in the Housing from what others have told me in the transmission rebuilding business.

Some I have talked to says it does not matter what Year or style of Reverse Input Drum I use in my Late 1987 700R4 Corvette trans rebuild.

Others say that I must use the correct late 1987-1992 Reverse Input Drum, Discontinued GM# 8681295.

And another said to Use the Revised GM # 24241494 OR #24245624 Reverse Input Drum(s) AND THEN USE THE CORRECT OR MATCHING FRONT PUMP STATOR HUB ASSEMBLY. The Stator Hub unbolts easily from my original 700R4 front pump assembly.

The Correct Stator Hub would be from a GM 4L60E or 4L65E or the 1993 only 700R4 transmission.

Any Auto transmission experts input and advice, what GM parts to use or High Quality aftermarket parts, will be greatly appreciated.

Is Pete K. Still around ?

He is the 700R4 Transmission expert here on C4 Corvette Forum from my readings

I have read many of his older postings here on Corvette Forum.

I have read no recent posts by him lately.

Perhaps he can best answer my question and What Reverse Input Drum to Use and stator shaft hub swap if indeed required.

Since the original GM # drum has been discontinued.

Thanks, Brian R.

 

GM is wrong. The late drum (square hole) replaces all [previous years with no stator swap need.
There are no ill effects of running the square hole drum. Be sure you have the matching aluminum piston, and install the bleed off orifice (restrictor) if it isn't already in it. If you need them, you will have to buy a pack of 5, and they are marketed through Teckpac. A local trans shop, or supplier should have one.

 

Thanks Pete.

There was too much confusion with what Reverse input to use to replace the original.

Do You actually Need Killer Hard Shifts in these C4 700R4 transmissions to make them last?

A few trans builders prefer very hard shifts.

This late 1987 YDM code trans allways had very good and quick positive 1-2, 2-3 shifts at part throttle, and WOT.

The 3-4 WOT shift was allways just OK.

But from reading your older posts, that is about normal with any 700R4 trans , so so 3-4 shifts.

I had the rear planetary gearset fail in the trans I am rebuilding now.

I have purchased All New GM 5-Pinion Front and Rear planetaries, ring gears, Sun gears, Needle thrust washers, And a GM Heat treated sun gear shell so far.

An entirely new GM geartrain minus reusing my original Output shaft.


Have You used the Newer Raybestos "Blue" 3-4 clutch packs ? are they overkill? Some say they can be used on the street. Others say track only.

I believe you prefer the Z-pack 3-4 clutches.

Others like the Red Alto 9- clutch packs.

My friend Jeff, a 20 + year trans builder prefers the Borg Warner rebuild kits allways with the Red Alto 9 clutch 3-4 pack himself. He stated all my options. He has never used the Raybestos "Blues" 3-4.

I am a spirited style driver. When space and no traffic allows, I stretch my 87 Vert. wide open for extended periods. Sometimes to 150+.

Other times I cruise normally for weeks. Then ocassionally I get the drag race bug in my system, play hard and kill another set of rear tires.

Any advice from you Pete is greatly apreciated by me.

Thanks, Brian R.

 

Well, after 10 minutes of typing a reply, the forum decided to wipe it out. So I will try again.

Firm is fine. As long as the clutch packs don't slip excessively, they live.

There is no such thing, in my opinion as too firm on the 3-4, so I lock the accumulator most of the time.

As far as the 5 pinion planets, you spent a bucket of money you didn't have to. I have 10 second cars running stock, tight, used 4 pinion GM planets.
Most rear planet failures are lube related, and not very common.
The cause is usually a worn bushing.

GM hardened reaction shells do fail occasionally. I prefer the beast. I saw a violent planet explosion be contained by the beast. The guy sanded out the burrs, and re-installed it.

My friction preferences are tan borg warners for everything, except the 3-4. I use the Z-Pack. So far, Z-Packs are holding up very well.

 

Hi Pete, I prefer to Overbuild Motors, Rear Differentials, and transmissions too Yes.

I am an auto mechanic by trade. Former GM mechanic. I never specialized In Auto trans rebuilds. I have overhauled maybe 10 in my time.

I am rebuilding this 700R4 Vette trans myself. I have aquired all the necessary Kent Moore factory tools over the past few months this winter.

I gave the Original 1987 Late 700R4 trans in my Corvette a Very Hard Thrashing that most Corvette owners dont do to them on the street for about 2 years straight. The original transmission lasted much longer than I ever expected it to.

It was on the advice of my friend Jeff, longtime transmission builder that I consider upgrading to GM 5-pinion front and rear planetaries and hardware needed for the swap out.

He has watched me Kill many GM and Ford built trannies over 20 years. He knows all too well how I drive at times.

I literally stripped all the teeth off of the Rear reaction 4-pinion planets and the rear reaction sun gear. Jeff said he has seen this before in all 700R4's and 4L60E's.

Did not look like a lubrication problem in my Vettes trans failure. He said that the rear planetary is also used in Overdrive - 4th. gear besides Low and Reverse.

Hard use and high speed driving for 2 years did it in I believe.

The rest of transmission looks very good yet.

I used Synthetic Royal Purple ATF in this Corvette trans the entire time I drove the car.

I believe that helped the stock 700R4 trans live longer than it should have under my hard use.

Many hate this synthetic ATF yes. I have friends using it in their Low 8-second 1/4 mile Renegade class Mustangs for years with no transmission issues what so ever. Built Ford C4 transmissions. Got me hooked on Royal Purple products.

I bought the New GM 5-pinion planets, Ring gears, and Sun Gears, Needle thrust bearings, and GM Hardened Sun Shell for a Very Good price.

I priced out all parts from GM at my discount, it was over $1,000.00.

I kept searching and found someone not far that had all NEW GM parts required to do the GM 4L65E 5-pinion forward and reaction gear swap out.

I saved nearly $650.00. Rather than buying from my local GM dealership I have been shopping from for the past 20 years.

All parts were in there original GM packaging, and has The factory Paint Swab markings on them.

I refuse to use China made parts in anything I build for myself or for other hotrodders and racers.

You just cant trust their inferior parts I found myself in the past. the market is just flooded with China made junk.

I see the money spent as an extra insurance and for future engine swap. Much more than my lightly modified L98 Tuned Port puts out now.

Is it a commen practice by You Pete to eliminate check *****, plug them throughout the transmission and then Drill or redrill required hole sizes needed throughout the transmission to meet your shifting needs ?

My friend Jeff does this Very Often on transmission builds, including the 700R4. And keeps telling me that the Corvette 700R4 is unique throughout compared to run of the mill 700R4's.

I scares me a bit to block off ball capsules, eliminate checkballs, drill specially sized holes in clutch pistons, and replace the special Factory GM valve body seperator plate with a Custom piece modified by my friend Jeff.

I should just trust him, but then again he keeps telling me that these C4 700R4's are all together unique , and especially the valvebody compared to any other 700R4.

Thanks again Pete, Brian R.

 

Yes Pete,

It is a debate that wont be resolved for some time to come. Synthetic trans Fluid verses Dextron III mineral based oil.

GM currently recomends Dextron VI in all there transmissions built to date 2010 and earlier.

Dex VI is a fully synthetic trans fluid. Mercon V , Ford ATF is a full synthetic.

Honda ATF is a full synthetic formulation.

Chrysler , MOPAR has their own ATF, DEX IV, I believe a synthetic fluid or a synthetic Blend.

Probably the best ATF ever made was the the OLD ancient Dextron, or Dextron I.

Made from Whale Oil. Sperm Whales. Enviromentalists and others made sure that formulation disapeared a long time ago.

Last time I seen Original Dex 1 for sale was 1984 or 1987.

I like the stuff yet, Royal Purple.

You may be correct it caused a failure.

Brian R.

 

Hi Pete!

Could you explain a little bit on that accumulator lock?!

 

Bruno,
The 3-4 accumulator piston is removed from the bore in the case, and a piece of steel sleeve is cut to space the piston. The spacer must be filed to size, so the 3 "fingers" on the piston are perfectly flush with the machined surface of the trans case. No spring is used.
B&M does this in their shift kits.

 

This Effectively eliminates the 3-4 Accumulator operation altogether then Pete ?

Would it not be easier then to just block the port(s) leading to the 3-4 accumulator assembly ?

Block it off with small allen screws red or green Loctited in place.

Or is that not a viable option or solution Pete ?

What type or brand of ATF do You prefer ? You are like my friend Jeff. He dont like synthetic transmission fluids also.

BR

 

Thanks Pete!

Souns like it might be worth doing while my engine and tranny are
out of the car.

 

hi, i gotta question about the reverse drum for 700r4, i saw the post on it, so its ok to use a reverse drum that has a 1993 large sqaure hole, and install it into a 87-92 700r4 that had a .095 hole drum Originally? and i notice the 93 has a added check ball for the larger hole. would i have to add that checkball to the 87-92 if i use that drum?

 

Hopefully Pete will see this thread and answer you. Havent seen Brian, (the OP) in a while. The mods will lock this thread after they see that its more than 45 days old. Do your search but dont reply to what you find. If you have a question after researching start a new thread if you want it to stay open long enough to get your questions answered.

PM Pete, he's kinda the tranny guru here. His Inbox may be full but keep trying and go ahead and post a new thread with your questions.

Good luck!

 

yes it was full, so i thought id try him on hear, but thank you for ur concern, i aprecate it

 

I have a brand new 8681295 reverse drum, If interested please e'mail me.
dennis
wit2n@juno.com

 

The post is 3&1/2 years old. He probably has the transmission built by now!!

 

thank you. I am new to this

dennis