MonteCarloSS.com

Transmission swap

Posted By: JYD

Transmission swap - 01/30/19 03:34 AM

Hello everyone,
I have recently been given a 1986 Monte with no motor and transmission.
I am intalling a gen 1 small block and have a 700r4 trans to install. Can anyone tell me what modifications I will need to do with the trans cross member?
Thank you.
Posted By: mmc427ss

Re: Transmission swap - 01/31/19 05:30 AM

Here's an old post from years ago that may be some help.
http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=762415&page=1
Bob
Posted By: JYD

Re: Transmission swap - 02/09/19 04:45 PM

Thanks Bob,

So this is what we did to the cross member to make it fit.. First of all we opened up the slot for the trans mount so we could slide it in place, to make the cross member fit level. We also had to remove about 1/4 inch of materal off of the left side of the cross member then installed the two bolts loose on the right hand side. then took a hole saw and drilled two new mounting holes on the left hand side of the frame rail.


My next obsicale is the speedo drive housing and drive shaft, which I have leads on both for soulutions.

As I continue to surpass these obsicales I will continue adding what I found to get the job completedand on the road.
Posted By: mmc427ss

Re: Transmission swap - 02/11/19 05:00 AM

As for the crossmember with any trans swap you try to get the tailhousing as high as possible. The engine/trans angle generally runs in the area of 3 1/4-1/2 degrees for most stock installs, sloping rearward. this is why the engine intake manifold has same angle front to rear.
Often the mistake is made when doing a trans swap to a trans not original to the chassis to just stick it in there. Mostly because some of these new trans are larger than the stock trans and require surgery on the tunnel to get them installed high enough into the tunnel to get that engine /trams angle.


What speedometer are you using, and is the donor trans an electronic speedo? This site may help with that problem.
Bob
Posted By: JYD

Re: Transmission swap - 03/19/20 02:14 AM

Hello Bob Thank you for the info.
It has been a while since I was on here last.
As for the speedo I am using the stock one to the car, the Trans is digital output. My plan is to get a Dakota box to convert it to analog.
Posted By: mmc427ss

Re: Transmission swap - 03/19/20 05:21 AM

Not sure if I linked any info about ways to adapt the speedo. Never doing that can't say what the easiest, cheapest or best way is. Several here have remedied it. The Dakota is one option I've seen, wow over 300 bucks. But you need a motor to drive the cable, power to drive it and something to converter pulse to revolutions, gets complicated. Some have swapped in a mech speedo tailhousing, swapped in a speedo gear from a same length 700.

Laying under a shelf in dark back corner of the shop is a 700R from an 87 IROC I bought, maybe 1993. The 86 had about about 40 K and I hated the 200R. Why wasn't it as smart as some of the TH350s I owned. At that time good 200R builds were scare and swapping in a 700R was done often. Yes when fresh maybe more durable than a 200 but you have to live with the ratio separation. That 3.06 1st gear is an rpm drop of 47%. The plus side of all that 1st ratio is quicker acceleration in 1st gear. Down side is that 47% rpm drop into 2nd from 5K drops to 2600. My 95 Astro has a 700R with 3.73 front and rear, Pretty peppy in 1st gear, with a "Corvette Servo" mod and it jumps into 2nd gear and falls on it's face trying to pull the sled. My wife 02 SS has a little less 1st, 2.92 but still has that 46% drop. With a 3.29 R&P accel is good in 1st gear but suffers the 2nd gear pull also. One fix for that is more torque down low with the 700R, more is better. The other fix to swap in a T56 with a 2.97 1st and only a 30% drop into 2nd.That's the reason the 700R is still in the dark corner.
Bob
Posted By: Hunter79764

Re: Transmission swap - 03/19/20 01:49 PM

There is also an option of using the "guts" from a Blazer (electronic) speedometer swapped over to the Monte dash/faceplate. I'm wanting to say it was a late 80's Blazer that worked, but there was a thread or two on here a while back.
Posted By: 86SS86LS

Re: Transmission swap - 03/20/20 02:37 AM

Originally Posted by Hunter79764
There is also an option of using the "guts" from a Blazer (electronic) speedometer swapped over to the Monte dash/faceplate. I'm wanting to say it was a late 80's Blazer that worked, but there was a thread or two on here a while back.


90-91 K5 Blazer or Suburban with 700r4 trans.

Here is a good write up:

https://gbodyforum.com/threads/electronic-speedo-conversion-pic-heavy.60194/
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