700R4 back to a 3 speed

[Big John Sny]

I know it is the wrong direction, but i am wanting to pull the poorly installed 700R4 from my truck and return it back to its three speed roots.

Someone at one time swapped the entire drivetrain from an 85 c10 into my truck. lots of bent, cut, welded crossmembers, the auto linkage utilizes part of the clutch pivot, ect.

My son could really use the 700r4 for his car at the moment, the flex plate on my truck has some damaged teeth and needs to probably be pulled anyways, and I found a rebuilt 67-72 era 3 speed and bell housing cheap, and the truck still has the 3 speed pedal assembly.

The problems I see are:
- I don't have the original column - is a 3 speed column going to be hard to find?
- I don't have the three speed driveshaft
- I do have some of the linkage for the clutch, but not all of it, and the clutch fork and clutch were missing in my 3 speed I found.
- I have 4:11 gears in the truck. I am assuming my freeway speed will be pretty limited without a R and P swap. I think the truck originally had a 3 speed with overdrive as I found a cable going back there from the cab that didn't seem to have a purpose. (this really was not a very clean swap)



If I can not source the column, and have to cut a hole in the floor anyways, I may take a look for a S10 T5 as it also cleans up some of the other issues, but I am thinking I would rather go column shift.

Just wanted to hear any advice, experience, ect.

[Steeveedee]

If you want to reinstall the 3 speed trans, you can buy a relatively inexpensive floor shifter. Finding an OD unit is like finding a unicorn. You'd be better off with a Gear Vendors OD, or something similar.

[LockDoc]

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I think you will need the bell housing cross member too..... It was probably removed when the 700 was installed.

LockDoc

[VetteVet]

My 700 was going south so I pulled it and installed a TH 350. You give up a little in mileage but I don't drive fast enough for the OD to kick in very often anyway.

With that 4:11 your engine will be screaming at 60. I'd pull that and swap in a 3:73 and sell or trade that 4:11. With the TH 350 and the rear end you'll still need a drive shaft. I can't see punching a clutch in traffic where I live, so the automatic was the only answer for me.
YMMV

[dennislbrooks]

Well, the 4.11 should work well with the OD - even if you do not use a lockup. If you are going to stay auto I would rebuild the 700r4 (if needed) and leave in truck and get another 700r4 for son's car. Unless free, switching rear diff gears will be close to price of stock rebuild.

The only truck I have without an OD runs 3.08 gears.

[Big John Sny]

Originally Posted by LockDoc

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I think you will need the bell housing cross member too..... It was probably removed when the 700 was installed.

LockDoc

Ha, I believe that was left in, but pushed back some so it can be in he way.
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[Big John Sny]

I actually enjoy standards, so I have no problem removing the auto. I believe I need a rear swap either way. I am in overdrive by 35 miles per hour with the 4:11s. I is a touch better since I got the torque converter lockup working, but I am turning pretty good RPM at 75 now.
I was thinking I might find someone that is building a truck for the strip that may want to swap ring and pinion with me out of another 12 bolt.
Even if I keep an overdrive (go with a T5 or something) I will still probably change up to 3:55s.
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[dennislbrooks]

With a 4.11, 30 inch tire, and .70 OD at 75 mph is about 2450 rpm. Taller tire will drop rpm more.

OD on a 700r4 should come in at about 45 mph under mild aceleration -- lockup right after unless switched.


With 3.55 gearing -- about 2200 rpm at 70 mph. This matches my 70 olds 442. Lockup will drop another 200 rpm.

My 67 K10 with 3.73 gearing and 31 inch tires runs about 1750 rpm at 60 mph with lockup. BBC --- averaged 14 mpg on a 200 mile trip.

Just numbers for consideration.

Not sure what OD is for a T5 but probably .7 or so. -- Nothing wrong with a stick. I have an 85 vette with 2 OD gears in a stick.

[Big John Sny]

Yeah, the 700R4 is going to my sons vette. He has one that has been gone through twice that they can’t find the issue with. Has the highly recommended trans guy from his shop stumped at the moment. Can’t find why it keeps burning up clutches. Maybe some crack opening up in the case under load or temp possibly. Feeling like taking my “known good” trans takes care of his issue without cutting up his 85 vette. Although, I think he would prefer going standard in it. The T56 swap would be best for his, but he was toying with swapping in a T5.
The thinking was, my swap is so bad in the truck, he could take my trans, not cut up anything in his car at the moment (maybe later when the right T56 deal comes up) and get a trans that has less mystery to it. Personally, standards have always been more “long term” reliable in all of my vehicles.

2200 rpm sounds nice. Using the truck to transport my race bike down to Houston and back to Dallas several times a year it would help with both fuel economy and sound levels. I am not racing anyone at the moment. Currently my speedo reads 100 mph while I am going 65. I think it is closer to 48 or so when the truck says 65 and sounds pretty nice from an engine rpm standpoint. I am assuming the 80’s drivetrain he pulled to stuff in this truck had 3:55’s and approximately the same wheel/ tire size.
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[dennislbrooks]

Not sure what year vette he has but will assume a 82-92. Clutching a non stick vette may be a chore. Everything is tight and hard to get to plus finding all the parts. When I lived in Dallas I picked up an extra 4+3 out of a wrecked 86. I think they used the 4+3 until 87 or 88. It is a good trans if properly maintained.

Good luck on your projects.

[Myoldtruck]

Sounds like your truck just needs a new flex plate, and some clean up work on linkage. Then your truck is still on the road. Your son needs a new transmission, if he can afford a corvette he can afford to buy a new trans on line that is beefed up. Give your son 500.00 towards his repair bill to help him out and you will be way ahead financially in the long run.

Doing the conversion on your truck to stick, doing it yourself will still set you back 750.00 to 1800.00 depending on the price of parts.

I did the 3spd to 4spd conversion. Trans and bellhousing, and high hump, 100.00 on craiglist. New drive shaft, 500.00. New clutch 125.00. Misc parts 75.00. Paying friend to help with heavy work, 60.00.

[Big John Sny]

The truck is worse than a flex plate and some linkage. It is really a bad swap. To do it right, it would require a different trans crossemember (75) the front crossmember removed correctly, linkage (250), wiring (just time), and the correct pedal assembly (100).

I think I am leaning towards a T5 swap. I would need a clutch fork (75$) and an s10 T5 with a Chevy pattern (300-400). The driveshaft should work and I would have to cut a hole in the floor.

My son works as a mechanic to pay his way through college and the vette was 1500 bucks. No the best idea to assume what others can afford.

I appreciate all of the advice on the swap. Was thinking more along the lines of specifics for this truck and less whether I should do a swap or not. Again, I appreciate all the advice.
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[Myoldtruck]

Sorry about assuming. Ask your son if he is having problems with his dash before he goes any further. Those years had a few gremlins in the dash that can be expensive to fix. Does the car have cross fire injection also.

For a daily driver I would go with the 5 speed also. With the o.d. 5th gear and the 4.11 gears you should be ok with 65mph range on the highway. I been looking at that same swap also, but I need to get the grease from under my fingernails from the last swap.

[Big John Sny]

All good.

He already rebuilt the dash and changed out the polarizers. Wasn't to bad since he did it himself. It looks really nice. I think it is a crossfire injection car.
He bought it with a bad trans that seemed a lot like a TV set up wrong. The TV was stuck. Got it unstuck and the 3-4 was dead. He pulled it and him and the transmission specialist at his shop went through it, but TV still didn't seem like it would set right and the 3-4 pack went again. They pulled it down again and the same person, who has an excellent reputation on these transmissions, went over it very closely trying to figure out what happened. They could not find any smoking gun, other than the bad clutches, of course. They built it back up but installed a kit to open up oil flow to the 3-4 pack. He has driven it for about 6 months commuting a pretty good distance for work and made several trips in it. It has felt ok to him, but not given him confidence. It dropped the 3-4 the other day on his way home from work (where he just put in notice so he can focus on his classes), he dropped to second and it was gone by the time he got home.

I think he is done trying to build this trans. There seems to be something wrong that is difficult to diagnose and he is a bit worn out with it. That is the reason I offered mine. At least it is known good. Not something he is going to be pulling in 6 months. That is one of the reasons he was really leaning towards a manual swap in the vette. He swapped a T5 for the 700r4 in his 88 camaro when he was 16, so he is pretty savvy on what it takes to do the swap and how much time/money that is involved in it, plus he was around the performance/restoration shop I worked in when he was a kid and has seen a lot of them done. My thought was just the truck is already such a bad hack job, and the vette is still pretty stock. why not use this as a chance to clean up a vehicle instead of having two chop jobs (even though I know he will do a much better job than the truck). I am wondering if the TV linkage in the vette trans has a different internal linkage for a different throw off of the throttle body or something like this. I thought I remember hearing something like that back when I was working on those.

I am actually having a lot more trouble finding a T5 than I used to. We have a spare one in the shop but it is later camaro so it has the Ford trans to belhousing pattern, but I think it is WC. Too bad it is not an S10 trans with the Ford pattern. I could just make my spacer plate also act as an adapter plate . There is always using the camaro bellhousing and fabricate a clutch throwout. Then I would have to use a s10 tailhousing and still use the funky kiltered Camaro shifter.

At the moment I will just keep my eye out for an early S10. If I could find a column and keep from hacking the floor in the truck I would still consider throwing a three speed in it for the moment since I already have it in the garage.

[RichardJ]

It doesn't really sound like the conversion problems with your truck will be fixed with a 3spd. only compounded.

Your 700r4 isn't a direct fit in the '85 vette. The output shaft is longer and the rear housing is different. The C4 doesn't use a rear trans mount. The trans bolts to an aluminum "C" channel that bolts to the front of the diff housing. The vette uses a different valve body, but would still work.

You need a better trans guy.

I have an '87 with the Doug Nash 4+3 that Dennmislbrooks mentioned. Still a basic small block, but with factory aluminum heads and roller cam.
I do love the car, but every time I spend money and time on it, I ask myself why and that's just to maintain a virtually stock, 167k mile car.

[RichardJ]

'85 should be the TPI, not the twin throttle body CrossFire.

[Big John Sny]

double post

[Big John Sny]

Originally Posted by RichardJ

It doesn't really sound like the conversion problems with your truck will be fixed with a 3spd. only compounded.

Your 700r4 isn't a direct fit in the '85 vette. The output shaft is longer and the rear housing is different. The C4 doesn't use a rear trans mount. The trans bolts to an aluminum "C" channel that bolts to the front of the diff housing. The vette uses a different valve body, but would still work.

You need a better trans guy.

I have an '87 with the Doug Nash 4+3 that Dennmislbrooks mentioned. Still a basic small block, but with factory aluminum heads and roller cam.
I do love the car, but every time I spend money and time on it, I ask myself why and that's just to maintain a virtually stock, 167k mile car.

I agree the 3speed won’t fix it on its own, just a better chance to clean things up. I don’t see it compounding problems. If I ran a three speed with 3.07s I think I would be fine. Not sure if that is what I am going to do. Going to be difficult to find all the parts, but also difficult to find everything I need to clean up the 700r4 swap too, so 6 one way and a half a dozen the other.

We figured we could change tailhousings to swap the transmissions.

I don’t doubt the skills of the transmission builder. Not at all. I do think there is something weird going on with the trans. I am assuming there is something like a crack in the case that is opening under load or temp. Something that is allowing the trans to test good but have some issues under use.
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[Big John Sny]

Looks like the crossmember is still there and riveted in place to put the original bellhousing back in.
Found the original fork for the clutch.

So, far I have a complete bellhousing, flywheel and rebuilt 3 speed for 110 dollars. Found the linkage and column for another 175 if I decide to go that way. Then I would need a driveshaft, clutch, and bellhousing mounts. With a little luck I could find a 3:07 rear end or adapt a R10 or R11 tailhousing on to my Saginaw box and be good to go.

I also have a 90’s Camaro T5. It has the Ford pattern mount to the bellhousing and the wrong tailhousing, but has the longer input shaft, so I could make an adapter/spacer plate easily on the lathe and mill, and adapt a mechanical s10 tailhousing. And then I would just need to buy a clutch.