New to fourm. V-6 vs V-8 & Manual vs Auto???

[pmercer]

I'm new to this forum and seek some advise.

I have a 1961 GMC 910 Step side short box with a 235 three speed. Rear end gears are 390. I recently installed power streering from a '81 chev and love it.

The problem I have is that with the above configuration the truck screams on the highway. I cruse with a group who all have V-8 automatics so they usually want to cruse at 60-70mph. At that speed my truck is at 3000-3500rpms.

I would like to keep the truck some what stock. I have sourced a 283 from a '65 pontiac and would love to install it in my truck. From reading some posts on this fourm, I think the 700 R4 automatic would be a good match.

So my questions are;
- Will the 700 R4 bolt up to the 283 or will I need some special adapter plate.
- Are all 283's the same. I have heard that some are different.
- Will the 700 R4 fit in my truck since it is a short box and pre'63.
- Other than the typical (yoke, drive shaft, engine mounts, trans mount) what else will I have to modify.

Thanks

Peter Mercer
St. John's Newfoundland Canada

[markeb01]

Addressing your first issue first, changing the rear end gear might be an easier and less expensive solution, especially if you want to keep the truck relatively stock. Not knowing if your truck is Canadian built, or if there are differences between Canadian and American made - American made 61 GMC's have Dana 44 rear axles. These are strong and remain very popular on Jeeps and Blazers, so getting someone to swap the gear set is an easy initial investment. Going from a 3.90 to a 3.08 or even a 3.31 will make a world of difference. You will need to have the carrier changed, as the 3.90 carrier is the break point for swapping to 4.09, 4.27 and lower gears.

If however you really want to change to an automatic, the gear change isn’t necessary. The 700R4 has a 0.7 overdrive in high gear, which would effectively reduce your final drive ratio to 2.73.

Some of your information is confusing. Does your truck currently have a 235 inline six, or is it the 305 GMC V6? Also, the 65 Pontiac, is that a Canadian build with a 283 Chevy engine in it?

If it truly is a Chevy 283, there are few differences. The 57 283 is unique having only front engine mount bosses for the cushion and stem type front engine mounts. 58-67 were essentially the same with conventional side engine mount bosses. The original 1955 small block 265 had different oiling at the rear cam bearing and used an external oil filter

I’m not personally familiar with the 700R4, but from everything I’m reading it appears the 700R4 will bolt up to a 283. It just needs the correct flexplate and matching starter. You will also need to fabricate a rear crossmember for the tailshaft mount.

Here’s a few links that explain technical details you might find helpful:

http://67-72chevytrucks.com/vboard/s...ighlight=700r4
http://67-72chevytrucks.com/vboard/s...ighlight=700r4
http://www.smokemup.com/tech/700r4.php
http://www.hotrodders.com/forum/700r...-a-111637.html

[padresag]

canadian gmc and pontiac in those years all used chev running gear
700r4 will not bolt up to a 235 I6 but will bolt up yo any 283 and to any 63 and up I6
in order to put a 700r4 in a 61 with any eng you will have to omit the crossmember under where the bellhousing mounts were and install a rear trans mount. you will also have to have side mounting on the eng- 3 point mounting
you could keep it as is and install a 3 speed o/d. bolt in replacement for the trans that you now have.
don't know what you have on there for tires, but you could install some larger tires(dia) which should cut your rpm a little.
ron

[pmercer]

Thanks for the replys guys.

My truck is a 235 I-6. I meant to say I-6 vs V-8 in thread title. My truck is a Canadian Truck. I thought about a rear gear change but I think the truck would really suffer on the hills then, with it being a three speed I couldn't really gear down or the rpm's would hit the roof.

How would I know if th 283 is a chevy or not. The engine is out of the car and the car is long gone.

Thanks

Peter

[padresag]

a 283 is a 283
3:08 may be a little high, but 3:4 or 3:7 would be quite manageable. this all depends on what you want to do with it. If your going to drive it as a car you can get away with 3:08s nand if you feel it lugging just put it in second
ron

[markeb01]

If you can get the casting number off the block, a check with one of many websites will identify what it is. Following is a Camaro site with a wealth of information. They are many others available via a Google search.

http://www.nastyz28.com/sbchevy/sblock.php