Engine crossmember forward, 72 k5,? before drill

[72 paul]

Well I know many have done this before and I have read many threads as to how far to move forward. Ive laid out 1 7/8 " for a 700 r, going to use stock xm.Before I drill it out would like to get some more input on best route to go for a solid deal.Kinda the measure 3 times and cut once thing.Thanks ahead for any replies. Paul.

[JMac11]

Seems like a few holes line up, loosened exhaust brackets slid motor forward, put in 700r4, bolted it back together. I have an LS now, different ball of wax

[4oldcars]

I have 350/700R4. I moved the bracket and re-drilled. Also re-sized the drive shaft. Had I to do again, I would keep the 350 trans. 700R4 is not worth the effort. Just my opinion.

[Bigdav160]

I went out and measured mine, yes, 1 7/8" inch. When did mine, I installed engine, crossmember and transmission. Clamped the crossmember to the frame and then drilled. It wasn't that easy even with all my tools.

[hemi43]

Just my 2 cents, but just installing a 700R4 by itself is a waste of time. The transmission is just one part that needs to be replaced to see any benefit. If you don't do an upgrade to your engine and gearing, your truck will be a dog. The camshaft and head design of the older 350 engines were most efficient with a cruising speed around 2500 RPM. Even if you upgrade your gearing to something like a 4.10:1 and had a 33"tall tire, your cruising RPM will be around 2000 which IMO is too low for that old engine. A nice drivable truck is the sum of all it's parts, and like a chain, will be as good as the weakest link.
What is your gear ratio, and your tire size ?
Dan

[Bigdav160]

I'm not sure I'd call it a waste of time. The gearing in third is the same 1:1 ratio as the original transmission. So performance is the same there. While not as deep as a manual transmission granny gear, first gear in the 700R4 is certainly better for take off. How many millions of trucks did GM build with anemic 150-200hp engines (carb and TBI) with a 700R4 and highway gears?

The benefit to a 700R4 retrofit is more comfortable cruising at highway speeds, longer engine life and a couple miles to the gallon at the pump.

[jjzepplin]

I agree. But then I have a built 406 and I built my 700r4 with many upgrades. Overdrive and lockup were nice to have when I drove it to Florida from Cali. Maybe that's why my 16 year old engine still runs like new. 4.10's too.
Seems like I remember the one side hole lined up so I used a right angle drill to drill the holes. I used needle nose vise grips to hold the member and mark where I needed to drill. Makes it real easy to work on the engine.

[hemi43]

Originally Posted by Bigdav160

I'm not sure I'd call it a waste of time. The gearing in third is the same 1:1 ratio as the original transmission. So performance is the same there. While not as deep as a manual transmission granny gear, first gear in the 700R4 is certainly better for take off. How many millions of trucks did GM build with anemic 150-200hp engines (carb and TBI) with a 700R4 and highway gears?

The benefit to a 700R4 retrofit is more comfortable cruising at highway speeds, longer engine life and a couple miles to the gallon at the pump.

I agree with what you're saying, but the example you gave above uses an engine that was designed to cruise at 2000 RPM, and those trucks came with either 3.42 or 3.73 gears. My original comment was to inform the OP that just bolting a 700R4 may not have the results he expected.
I have no idea what equipment the OP has on his truck, but for example if he has the original 3.08 gears and is running 33" tires, his engine RPM @ 60 MPH would be around 1300 RPM, which would not work.

[72 paul]

Hemi43, very nice truck you did there.Well not just putting this 700r in behind a tired old 350,will have 400 to 450 hp when done, good guts k case 700r 205,33s with 373s.Looking to do about the same as what jjzepplin described. Highway usage but not afraid to wheel.Drove truck for about 5 years, tore it down May of 15 and going back together now. I did get the drillin done.Guess Iwas a little skeptic on diving in.Thanks for replies everyone. Paul.

[hemi43]

Originally Posted by 72 paul

Hemi43, very nice truck you did there.Well not just putting this 700r in behind a tired old 350,will have 400 to 450 hp when done, good guts k case 700r 205,33s with 373s.Looking to do about the same as what jjzepplin described. Highway usage but not afraid to wheel.Drove truck for about 5 years, tore it down May of 15 and going back together now. I did get the drillin done.Guess Iwas a little skeptic on diving in.Thanks for replies everyone. Paul.

Thanks for the comment, Paul !!
I'm also running 33's, and have 4.10 gears. IMO, this is the perfect combination with an OD transmission. I have way more bottom end power than I need, and cruise around 1900 RPM. The last trip I went on I averaged 24.6 MPG.
3.73 gears may still be a bit too stiff with those tall tires IMHO.