Need help with Engine transplant

[FL71C10]

I have a 71 SB with no motor (5 lug disk brakes, PS). It was originally a V8 automatic truck. It has no front end on it yet, but I am working on finding a front clip or a donor truck. I just bought a 68 shortbed truck for the bed, and it has a 6 cyl 3 speed manual transmission. The PO said the engine runs. Obviously I will verify that before I do anything with the engine. I really don't want to covnert my automatic truck over to manual for a three on the tree setup. How big a deal would it be to convert the engine to an automatic and put it in the truck? Should I even consider it? I am not hung up on having a V-8.

I would consider a 4 speed or 5 speed from a late model truck but am not sue that it would fit. For that I wouldn't mind switching out the pedal, etc. Will the 68 pedal setup work in my 71 truck? Any advice?

Thanks!

[GruntMoanCough]

Your 6 cyl should just bolt right in, swapping flywheel for flex plate. I presume that you have the auto trans still in your '71.

[FL71C10]

Unfortunately not. Do I just get a flexplate from a jukyard? Will the starter be the same? Any distributor or carb changes necessary due to the trans change?

Thanks!

[GruntMoanCough]

I would suggest a new flex plate but, maybe a used trans, flexplate, starter and carb/shifter linkage from a wrecker would work for you.

BTW.........Welcome!

[raycow]

Any automatic that works on a V-8 will also fit your six. You will not be able to use your manual starter. Find your flexplate first and then the starter because the starter needs to match the flexplate. You will also need an automatic radiator, oil cooler lines, and shift and kickdown linkage if any of these did not come with the 71 truck.

It might be less work/money to swap your manual transmission parts over to the 71 truck. You can get 4 and 5 speed transmissions that will bolt up to your stock bellhousing. My first choice would be a 5 speed from a 92 or earlier S-10.

Ray

[garyed08]

did one of these automatic swaps on my 250. Royal Pain in the rear. i put a 350 turbo behind my 6 cylinder. i had to move the motor ahead just to get my drive shaft to fit. drill new holes for the motor mounts. royal pain to find a starter for. cause the 250 has the inline holes not staggered. it can be done but its a royal PITA. 2 weeks later i put a rod through the block and converted it to a V8 anyways. not to mention taking the spacer block off the fan so it doesnt hit the radiator

[junkyardjohn]

IT'S NOT TO TOUGH AT ALL. DON'T GET HUNG UP ON THE DRIVE SHAFT ISSUE. THEY'RE CHEAP TO HAVE RE-TUBED & EVEN CHEAPER IF YOU JUST NEED IT SHORTENED. THE YOKES ARE THE EXPENSIVE PART. GOING FROM A MANUAL TO AN AUTO-MATIC IS THE SIMPLEST WAY, ESPECIALLY IF YOU HAVE A DONOR TRUCK. STOCK FLEX-PLATES ARE CHEAP & EASY TO FIND AT ANY DECENT AUTO-PARTS STORE. JUST INSPECT THE WELDS WHERE THE RING GEAR IS WELDED TO THE BODY OF THE FLEX PLATE. (SOME OF THEM LOOK LIKE THEY WERE WELDED BY ME.) I WOULD MAIL YOU ONE FOR FREE BUT IT PROBABLY COSTS MORE TO SHIP THAN ITS WORTH. BUY A GOOD ASSEMBLY MANUAL, BONE UP ON THE COMPONENTS & DIVE RIGHT IN. THERES AN AWFUL LOT OF HELPFUL INFO. RIGHT HERE, BUT YOU KINDA HAVE TO SEPARATE THE B.S. FROM THE FACTS. GOOD LUCK WITH YOU'RE PROJECT. JOHN

[FL71C10]

Thanks for all of the advice, guys. Raycow, I am interested in your advice that it may be easier to move the manual trans stuff over to the 71, and put in a later model 5 speed. Why a 92 or later 5 speed? Does it matter if it was a 4 cyl or 6 cyl truck?

So I would use my bellhousing and just bolt the new trans on the back? Will my clutch hardware work on that transmission? Will I need a new crossmember? Am I asking too many questions?

I hope the manual trans cross member from the 68 would work on the 71.

Thanks!

[truckdude239]

all late models 5 speeds require some minor mods seeing the clutch hardware is hydraulic and the older stuff is manual linkage

[rsavage]

Pretty sure that if your truck was born as an automatic, you will need to take the stick crossmember with the bell housing mounts from the donor truck and transplant it into yours. I've gone the other way - stick to automatic and had to remove the rear engine (bellhousing) crossmember and put in an automatic crossmember for the transmission.
Easiest transplant will be a V8 and an auto - what the truck originally came with. You will probably spend as much trying to convert than you would finding a good running used 350 engine and TH 350 trans.

[FL71C10]

What do you guys think I should pay for a used 350 with a turbo 350? I have found a few complete vans with 90000 or less mild on them for $400 or $500.
I heard that vans use different motor mounts.

Could I use the van tilt wheels in the truck as well?

[raycow]

Originally Posted by FL71C10

Why a 92 or later 5 speed? Does it matter if it was a 4 cyl or 6 cyl truck?

So I would use my bellhousing and just bolt the new trans on the back? Will my clutch hardware work on that transmission? Will I need a new crossmember? Am I asking too many questions?

I hope the manual trans cross member from the 68 would work on the 71.

The T-5 needs to be 92 or EARLIER in order to bolt to your stock bellhousing. Either 4 cyl or V-6 will work. The bolt pattern on the T-5 changed in 93 and the bellhousing you would need for the later transmissions is very scarce. You can't use the stock bellhousing from the S-10.

You will need to replace your clutch disc. Keep your stock bellhousing crossmember, clutch linkage, fork, throwout bearing, pressure plate, etc.

The T-5 input shaft is longer than the one on your stock 3 speed. You can either shorten the shaft or use a spacer plate between the transmission and bellhousing. If you decide to shorten the shaft instead of using a plate, you will need a step ring to take up the difference in the center hole diameter (the ring is needed only if you have a 68 or later bellhousing).

I can recommend this guy for the spacer plate because he makes them up to order. Just tell him you are using a truck bell with the 5-1/8" center hole.
http://www.inliners.org/buffalo/index.htm

There are other vendors for the plate, but make sure they understand about the center hole before you order from them. If you want to go the step ring route, those are available from Novak, Advance Adapters, and others. It is also an easy job for any machine shop to make the ring

Don't worry about asking too many questions. It's the people who DON'T ask questions that get into trouble.

Ray

[FL71C10]

Thanks for the info, Raycow.

Are the gear ratios for the 4 cyl and 6 cyl transmissions the same? Do you think I'll end up having to change my rear end gears on the 71? I imagine with an original V8 automatic it would be a 3.08?

So what clutch disc do I get? One for the s10 or one for the 71? If i keep everything else, then I can use all of the clutch mechanism parts from the 68 and move it over to the 71, right? No issues with hydraulic clutches, etc?

Do I need to get the driveshaft from the S-10 so I have the yoke? What about the speedometer cable hookup? Will it be the same?

Any idea how much that plate costs?

Thanks again for the info.

[FL71C10]

Raycow, thanks for the excellent info. So, there's no issue with gear ratios in the transmission from a 4 cyl vs 6 cyl? I know I was going to put a T-5 in my old mustang, and I was told that the gear ratios for the 6 cyl transmissions were too high and the car would drive like a farm truck.

Do I need to get the driveshaft from the 5 speed truck as well? What about the speedometer? Will I have to make mods to make that work?

What clutch disc do I need? One from an S-10, or another one altogether? So my clutch linkage, etc from the 68 will transfer over to the 71 and will work using the original bellhousing?

Thanks again for your time.

John

[raycow]

GM used a bunch of diffferent gear ratios in the T-5. If you find one that still has its ID tag, this chart might help sort out what it has inside.
http://www.britishv8.org/Articles/Bo...T5-ID-Tags.htm
If the tag is missing, you can get an approximate idea of the ratios by shifting it into different gears and turning the shafts.

Your 6 cyl will be ok if you have 3.08 gears. That was a factory option with the 6. The only question is how it will like the O/D. The tallest gearing I have run with a 6 was 3.55 with a 0.70 O/D. That one would pull smoothly in O/D down to about 25-30 mph. Of course the whole point of having O/D is that you can downshift it when conditions require. It was never intended that the O/D should be used all the time.

You will need an Astrovan, Camaro, or S-10 clutch disc, depending on what diameter your pressure plate is. The disc will have 14 splines to fit the T-5 input shaft. Your stock transmission has 10 splines. You definitely will not need hydraulic clutch linkage. That's one of the main advantages of keeping your stock bellhousing.

The S-10 T-5 has the common 27 spline output shaft used on most other GM transmissions. Your stock 3 speed yoke should fit it. You will probably need to shorten the driveshaft though - or look for a correct length shaft in a salvage yard, which is what I did.

Your stock speedo cable will screw on to the T-5 gear fitting, but the cable may be too short. In that case, you can use a cable for an automatic or a 4WD and it will reach. Some of the later transmissions have an electric speedo drive. If you get one of those you can pull it out and replace it with the fitting and gear for a mechanical drive. The one from your 3 speed should fit, but you might have to replace the gear if your speedo reads incorrectly.

Here is another vendor that offers the spacer plate, and this site has pics showing what it looks like. Their price is $130. Buffalo was about the same price the last time I asked, but that was a couple of years ago.
http://hamiltonintakes.com/products/s10t-5-adapter.html

Ray

[FL71C10]

Originally Posted by raycow

The T-5 needs to be 92 or EARLIER in order to bolt to your stock bellhousing. Either 4 cyl or V-6 will work. The bolt pattern on the T-5 changed in 93 and the bellhousing you would need for the later transmissions is very scarce. You can't use the stock bellhousing from the S-10.

You will need to replace your clutch disc. Keep your stock bellhousing crossmember, clutch linkage, fork, throwout bearing, pressure plate, etc.

The T-5 input shaft is longer than the one on your stock 3 speed. You can either shorten the shaft or use a spacer plate between the transmission and bellhousing. If you decide to shorten the shaft instead of using a plate, you will need a step ring to take up the difference in the center hole diameter (the ring is needed only if you have a 68 or later bellhousing).

I can recommend this guy for the spacer plate because he makes them up to order. Just tell him you are using a truck bell with the 5-1/8" center hole.
http://www.inliners.org/buffalo/index.htm

There are other vendors for the plate, but make sure they understand about the center hole before you order from them. If you want to go the step ring route, those are available from Novak, Advance Adapters, and others. It is also an easy job for any machine shop to make the ring

Don't worry about asking too many questions. It's the people who DON'T ask questions that get into trouble.

Ray

Raycow,

A couple more questions:

No issues with gear ratios on a 4 cyl trans vs a 6 cyl one?

Do I need to get the driveshaft from the S-10 so I have the front yoike, or will my old one work?

So if i am using the old bellhousing and other clutch hardware, my donor truck pedals, etc should bolt in to the 71 amd I won't need to make any mods there?

What clutch disc do I need to get?

Any idea how much that spacer will run me?

Thanks!

John

[raycow]

Originally Posted by FL71C10

Raycow,

A couple more questions:

No issues with gear ratios on a 4 cyl trans vs a 6 cyl one?

Do I need to get the driveshaft from the S-10 so I have the front yoike, or will my old one work?

So if i am using the old bellhousing and other clutch hardware, my donor truck pedals, etc should bolt in to the 71 amd I won't need to make any mods there?

What clutch disc do I need to get?

Any idea how much that spacer will run me?

Thanks!

John

Looking at the ratio chart, it appears that on some models the same transmission was used on both the 4 and the 6. On others, the 4 had somewhat lower (numerically higher) gearing. Any of them would give you plenty of 1st gear for starting off, even if you have a 3.08 rear. 1st gear in the most common 3 speeds was only 2.94 or 2.85, depending on whether or not it had synchro. If you are concerned about the gaps between gears, any of them will be closer than on your 3 speed.

I am pretty sure the entire pedal assembly should swap between the two trucks. IIRC, the 71 has a different throttle arrangement that uses a cable, but I don't believe that would affect the other pedals. The only possible issue I can think of is that if one had PB and the other didn't, then you might need to get a different pushrod.

Oh, and the automatic truck won't have the frame bracket for the clutch cross shaft. You can cut the bracket off the stick shift truck, but I believe that bracket is reproduced and it would be less work to just buy a new one.

On the clutch disc, your 6 could have either a 10" or 11" clutch. It's best to wait till you get it apart, but you can get a rough idea by looking now. Take the bottom cover off the bellhousing and look at the pressure plate near one of the screws. If the outer edge of the stamping is almost touching the edge of the flywheel, you have the 11". If there is a space of about 1/2" or so, it's the 10".

I believe your other questions are answered in my previous post.

Ray